Method for preparing niobium-iron alloy through electrolysis of niobium concentrate

Abstract

The invention provides a method for preparing a niobium-iron alloy through electrolysis of niobium concentrate, and belongs to the technical field of non-ferrous metallurgy refining. The method comprises the steps that firstly, under the protective atmosphere, niobium concentrate is dried, electrolyte is obtained, and the main components of the niobium concentrate are silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and ferric oxide; and then electrolyzing the electrolyte to obtain the niobium-iron alloy. According to the method, the niobium concentrate subjected to rare earth extraction and efficient iron removal serves as the raw material, the molten oxide-fluoride system is adopted for electrolysis to prepare the niobium-iron alloy, the electrolysis process is effectively controlled, the high-quality niobium-iron alloy can be obtained, and separation of niobium and titanium is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal metallurgy and refining, and in particular to a method for preparing ferroniobium alloy by electrolyzing niobium concentrate. Background Art

[0002] Niobium has good superconductivity, high melting point, corrosion resistance and other physical properties, and is widely used in aerospace, atomic energy, biotechnology, superconducting materials, metallurgy and steel industries. In recent years, with the rapid development of high-tech fields such as nuclear energy industry, aerospace and medical surgery, the demand for niobium has begun to grow year by year, making niobium a vital strategic metal. Niobium iron alloy is an important component of high-temperature resistant alloys, stainless steel materials and high-strength low-alloy steel, accounting for 80% of the total niobium consumption. At present, my country's dependence on imported niobium resources from overseas is as high as 95%.

[0003] The Bayan Obo mine is a world-famous polymetallic symbiotic deposit with iron, rare earth and niobium, which has extremely high comprehensive utilization value. The potential reserves of niobium in the Bayan Obo deposit are 6.6 million tons. The mineral resources of Bayan Obo are characterized by large reserves, multiple types, low grade, fine crystal size and complex mineral composition, which bring great difficulties to separation and extraction. After the beneficiation of iron and rare earth, the remaining niobium resources in the tailings have not been fully extracted, resulting in almost zero utilization of niobium resources. At present, the commercial smelting processes for producing metallic Nb include aluminothermic reduction of Nb2O5, carbon thermal reduction of Nb2O5 and sodium reduction of K2NbF7. However, the traditional smelting process is only suitable for processing high-grade niobium concentrate (>50%), but it is not economical for processing low-grade niobium ore, especially the extremely low-grade niobium ore (0.1%) like Bayan Obo. The mineral composition characteristics and grade differences determine that it is difficult to extract niobium using traditional smelting processes. Baosteel Group once used the "high-speed-to-electricity-electricity" process to obtain low-grade niobium ferrotitanium alloy by carbon thermal reduction of low-grade niobium concentrate. Niobium ferrotitanium alloy has no application in the steel industry, and the alloy cannot separate niobium and titanium, so the technology was not further developed.

[0004] The melt electrolysis method has become a potential method to replace traditional smelting due to its advantages such as short process flow, low cost, continuous production and high product purity. Many researchers have begun to study the electrochemical behavior of niobium ions in fluoride and chloride melts in the mid-20th century. Since niobium ions have multiple valence states in the melt, the reaction during the electrochemical reduction process is quite complicated. Due to factors such as electrolytes, electrolysis conditions and different sources of niobium ions (Nb2O5, NbCl5 and K2NbF7), the study found that the reduction process of niobium ions also has certain differences. Their common feature is that they are a gradual reduction process. In 1998, Fray et al. proposed a new concept called solid cathode electro-deoxidation, namely the FFC method, which uses metal oxides as cathodes, obtains electrons during the electrolysis process and is reduced to metals, and oxygen ions migrate to the anode to be oxidized to oxygen. In 2005, Fray et al. conducted a study on the direct reduction of Nb2O5 in a chloride melt using the FFC method. However, both the melt electrolysis method and the FFC method mentioned above require pure niobium oxide powder as the electrolysis raw material, and cannot be directly applied to the niobium electrolysis of mineral raw materials. Therefore, it is of great significance to study a method for preparing niobium iron alloy by electrolysis of niobium concentrate and to obtain high-quality niobium iron alloy using low-grade niobium ore. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing niobium-iron alloy by electrolysis of niobium concentrate, so as to solve the problem that niobium cannot be extracted from low-grade niobium ore in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing ferroniobium alloy by electrolysis of niobium concentrate, comprising the following steps:

[0008] (1) Drying the niobium concentrate under a protective atmosphere to obtain an electrolyte;

[0009] The main components of the niobium concentrate are silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and iron trioxide;

[0010] (2) Electrolyzing the electrolyte to obtain niobium-iron alloy.

[0011] Preferably, in the step (1), the mass ratio of silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and ferric oxide is 20-40:20-40:10-30:5-15:5-20:2-10; and the niobium concentrate is Bayan Obo niobium concentrate.

[0012] Preferably, in step (1), the drying temperature is 100 to 500° C., and the drying time is 2 to 60 hours.

[0013] Preferably, in step (1), the protective atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0014] Preferably, in step (2), the electrolysis temperature is 1200-1700° C., the electrolysis time is 1-48 h, and the heating rate to the electrolysis temperature is 3-6° C. / min.

[0015] Preferably, in the step (2), the electrolyte is heated to the electrolysis temperature, the obtained electrolyte melt is subjected to a heat preservation treatment at the electrolysis temperature and then electrolyzed, wherein the heat preservation treatment time is 30 to 240 minutes.

[0016] Preferably, in step (2), during electrolysis, a tungsten wire or an iron rod is used as the cathode, and an inert electrode is used as the anode; the area ratio of the anode to the cathode is 4 to 8:1.

[0017] Preferably, the diameter of the iron rod is 1-6 mm; the diameter of the tungsten wire is 1-3 mm; and the inert electrode is a graphite electrode, a glassy carbon electrode, a platinum electrode, a platinum-rhodium electrode or an iridium electrode.

[0018] Preferably, the method for pre-treating the tungsten wire or the iron rod is: grinding and polishing, acid immersion, and ultrasonic cleaning the tungsten wire or the iron rod in sequence.

[0019] Preferably, the current density of the electrolysis is 0.1 to 3.0 A / cm 2 .

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention uses niobium concentrate from which rare earths have been extracted and iron has been efficiently removed as a raw material, and adopts a molten oxide-fluoride system for electrolysis to prepare ferroniobium alloy. By effectively controlling the electrolysis process, not only high-quality ferroniobium alloy can be obtained, but also niobium and titanium can be separated. The obtained ferroniobium alloy is a titanium-free ferroniobium alloy.

[0022] (2) The present invention can deeply extract the remaining iron and niobium in the tailings. The technical solution is simple to operate and has strong operability, which realizes the efficient preparation of niobium-iron alloy, thereby reducing the energy consumption of the entire niobium-iron alloy preparation and achieving good economic benefits.

[0023] (3) Compared with the conventional blast furnace electric furnace smelting method of ferroniobium alloy, the present invention uses a suitable inert anode to electrolyze the electrolyte melt, which will release less carbon dioxide and even achieve zero carbon dioxide emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1Schematic diagram of the electrolysis device used for electrolyzing the electrolyte melt in the present invention, wherein 1 is an anode, 2 is a cathode, 3 is an alumina protection tube, 4 is a water-cooling flange, 5 is a boron nitride crucible, 6 is a heating element, 7 is a reference electrode, 8 is a heating furnace, and 9 is an electrolyte melt;

[0025] Figure 2 This is a SEM image of the ferroniobium alloy prepared in Example 1;

[0026] Figure 3 This is the EDS image of the ferroniobium alloy prepared in Example 1, wherein Figure 3 Point1 in Figure 2 Point 1, Point 2 corresponds to Figure 2 Point 2, Point 3 corresponds to Figure 3 3 of 3;

[0027] Figure 4 is the XRD pattern of the ferroniobium alloy prepared in Example 1;

[0028] Figure 5 This is the SEM-EDS image of the ferroniobium alloy prepared in Example 2;

[0029] Figure 6 This is the SEM-EDS image of the ferroniobium alloy prepared in Example 3;

[0030] Figure 7 This is the SEM-EDS image of the niobium-iron alloy prepared in Example 4. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing ferroniobium alloy by electrolysis of niobium concentrate, comprising the following steps:

[0032] (1) Drying the niobium concentrate under a protective atmosphere to obtain an electrolyte;

[0033] The main components of the niobium concentrate are silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and iron trioxide;

[0034] (2) Electrolyzing the electrolyte to obtain niobium-iron alloy.

[0035] In the present invention, in the step (1), the mass ratio of silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and ferric oxide is 20-40:20-40:10-30:5-15:5-20:2-10, preferably 25-38:25-37:15-25:6-12:8-12:4-8, and more preferably 30.9-34:30.2-34:20-22:6-8:10:4-6; the niobium concentrate is Bayan Obo niobium concentrate.

[0036] In the present invention, in step (1), the drying temperature is 100 to 500° C., preferably 180 to 300° C., and more preferably 200 to 240° C.; the drying time is 2 to 60 h, preferably 20 to 50 h, and more preferably 35 to 42 h.

[0037] In the present invention, in step (1), the protective atmosphere is an argon atmosphere or a nitrogen atmosphere, preferably an argon atmosphere.

[0038] In the present invention, the niobium concentrate is preferably ground after being dried.

[0039] In the present invention, in the step (2), the electrolysis temperature is 1200-1700°C, preferably 1300-1500°C, and more preferably 1350-1470°C; the electrolysis time is 1-48h, preferably 1h, 2h, 8h, 10h, 20h, 30h, 40h, 48h, and more preferably 1h, 2h, 8h, 48h; the heating rate for heating to the electrolysis temperature is 3-6°C / min, preferably 3.5-5.5°C / min, and more preferably 4-5°C / min.

[0040] In the present invention, in step (2), the electrolyte is heated to the electrolysis temperature, and the obtained electrolyte melt is subjected to a heat preservation treatment at the electrolysis temperature before being electrolyzed, wherein the heat preservation treatment time is 30 to 240 minutes, preferably 60 to 180 minutes, and more preferably 90 to 120 minutes.

[0041] In the present invention, in step (2), during electrolysis, a tungsten wire or an iron rod is used as a cathode, and an inert electrode is used as an anode; the area ratio of the anode to the cathode is 4 to 8:1, preferably 6 to 7.5:1, and more preferably 6 to 7:1.

[0042] In the present invention, the purity of the tungsten wire is 98-99.99%, preferably 98.5-99.95%, and more preferably 99.5-99.9%; the purity of the iron rod is 98-99.99%, preferably 98.5-99.95%, and more preferably 99.5-99.9%.

[0043] In the present invention, the diameter of the iron rod is 1-6 mm, preferably 2-5 mm, and more preferably 3-4 mm; the diameter of the tungsten wire is 1-3 mm, preferably 1.5-2.5 mm, and more preferably 2 mm; the inert electrode is a graphite electrode, a glassy carbon electrode, a platinum electrode, a platinum-rhodium electrode or an iridium electrode, and is preferably a graphite electrode.

[0044] In the present invention, the method for pre-treating the tungsten wire or the iron rod is: grinding and polishing, acid immersion, and ultrasonic cleaning are sequentially performed on the tungsten wire or the iron rod.

[0045] In the present invention, during the grinding and polishing, the tungsten wire or iron rod is preferably polished with sandpaper of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh in sequence, and then immersed in dilute hydrochloric acid after grinding, wherein the immersion time is 1 to 3 hours, and after the immersion, it is preferably ultrasonically cleaned with anhydrous ethanol, wherein the ultrasonic power during ultrasonic cleaning is 100 to 500 W, preferably 200 to 400 W, and more preferably 300 W, and the ultrasonic cleaning time is 20 to 120 min, preferably 40 to 80 min, and more preferably 45 to 70 min.

[0046] In the present invention, the current density of the electrolysis is 0.1 to 3.0 A / cm 2 , preferably 0.5 to 2.5 A / cm 2 , more preferably 1.0 to 1.8 A / cm 2 .

[0047] In the present invention, the electrolysis is carried out in a protective atmosphere, which is an argon atmosphere or a nitrogen atmosphere, preferably an argon atmosphere.

[0048] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0049] Example 1

[0050] Take 120g of Bayan Obo niobium concentrate, whose main components and contents are: 37.8g SiO2, 30.2g CaO, 20.0g CaF2, 8g Nb2O5, 12g TiO2, 4g Fe2O3 and 8g other minerals, dry it at 210°C for 36h in an argon atmosphere, and then grind it in an agate mortar to obtain an electrolyte.

[0051] A tungsten wire with a diameter of 2 mm (purity of 99.5%) was polished with sandpaper of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh in turn, then immersed in dilute hydrochloric acid (mass concentration of 10%) for 2.5 h, and finally ultrasonically cleaned with anhydrous ethanol for 50 min (ultrasonic frequency of 300 W) to remove organic matter on the electrode surface.

[0052] The pretreated tungsten wire was used as the cathode and the graphite electrode was used as the anode, and the area ratio of the anode to the cathode was 8:1.

[0053] The electrolyte was transferred to a boron nitride crucible and placed in an electrolysis device. In an argon atmosphere, the heating furnace was heated to 1470°C at a heating rate of 4.5°C / min. The electrolyte melt was kept at 1470°C for 90 minutes. After the end of the heat preservation, a 1.8A / cm 2 The electrolyte melt was electrolyzed at 1470°C for 2 hours with a cathode current. After the electrolysis, the melt was slowly cooled with the furnace. After the temperature dropped to room temperature, the solidified electrolyte in the boron nitride crucible was taken out to obtain niobium-iron alloy at the bottom of the electrolyte.

[0054] The SEM image of the niobium-iron alloy prepared in this embodiment is as follows: Figure 2 As shown, Figure 3 For the EDS diagram, Figure 3 It can be seen that the ferroniobium alloy mainly includes Fe, Nb and Nb-Fe alloy. The atomic ratio of Nb and Fe in the Nb-Fe alloy is close to 1:2. The obtained ferroniobium alloy is mainly Fe2Nb without titanium. Figure 4 The XRD pattern of the ferroniobium alloy prepared in the embodiment is shown in FIG. Figure 4 It can be seen that the prepared ferroniobium alloy is mainly composed of Fe and Fe2Nb alloy, and also contains a small amount of FeNb alloy.

[0055] Example 2

[0056] Take 120g of Bayan Obo niobium concentrate, whose main components and contents are: 34g SiO2, 34g CaO, 22.0g CaF2, 8g Nb2O5, 10g TiO2, 6g Fe2O3 and 6g other minerals, dry it at 200°C for 42h in an argon atmosphere, and then grind it in an agate mortar to obtain an electrolyte.

[0057] A tungsten wire with a diameter of 2 mm (purity of 99.95%) was polished with sandpaper of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh in turn, then immersed in dilute hydrochloric acid (mass concentration of 10%) for 3 h, and finally ultrasonically cleaned with anhydrous ethanol for 60 min (ultrasonic frequency of 200 W) to remove organic matter on the electrode surface.

[0058] The pretreated tungsten wire was used as the cathode and the graphite electrode was used as the anode, and the area ratio of the anode to the cathode was 7:1.

[0059] The electrolyte was transferred to a boron nitride crucible and placed in an electrolysis device. In an argon atmosphere, the heating furnace was heated to 1450°C at a heating rate of 5°C / min. The electrolyte melt was kept at 1450°C for 60 minutes. After the end of the heat preservation, a 0.1A / cm 2The electrolyte melt was electrolyzed at 1450°C for 48 hours with a cathode current. After the electrolysis, the melt was slowly cooled with the furnace. After the temperature dropped to room temperature, the solidified electrolyte in the boron nitride crucible was taken out to obtain niobium-iron alloy at the bottom of the electrolyte.

[0060] The SEM-EDS image of the ferroniobium alloy prepared in this embodiment is as follows: Figure 5 As shown, EDS analysis shows that the atomic ratio of Nb and Fe is close to 1:1, there is no titanium, and the obtained niobium-iron alloy is mainly FeNb.

[0061] Example 3

[0062] Take 110g of Bayan Obo niobium concentrate, whose main components and contents are: 30.9g SiO2, 37.1g CaO, 20.0g CaF2, 6g Nb2O5, 8g TiO2, 4g Fe2O3 and 4g other minerals, dry it at 300°C for 40h in an argon atmosphere, and then grind it in an agate mortar to obtain an electrolyte.

[0063] A tungsten wire with a diameter of 3 mm (purity of 99.99%) was polished with sandpaper of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh in turn, then immersed in dilute hydrochloric acid (mass concentration of 10%) for 2 h, and finally ultrasonically cleaned with anhydrous ethanol for 45 min (ultrasonic frequency of 400 W) to remove organic matter on the electrode surface.

[0064] The pretreated tungsten wire was used as the cathode and the graphite electrode was used as the anode, and the area ratio of the anode to the cathode was 7.5:1.

[0065] The electrolyte was transferred to a boron nitride crucible and placed in an electrolysis device. In an argon atmosphere, the heating furnace was heated to 1430°C at a heating rate of 3.5°C / min. The electrolyte melt was kept at 1430°C for 120 minutes. After the end of the heat preservation, a 1.0A / cm 2 The electrolyte melt was electrolyzed at 1430°C for 8 hours with a cathode current. After the electrolysis, the melt was slowly cooled with the furnace. After the temperature dropped to room temperature, the solidified electrolyte in the boron nitride crucible was taken out to obtain niobium-iron alloy at the bottom of the electrolyte.

[0066] The SEM-EDS image of the ferroniobium alloy prepared in this embodiment is as follows: Figure 6 As shown, EDS analysis shows that the ferroniobium alloy is mainly FeNb alloy.

[0067] Example 4

[0068] Take 112g of Bayan Obo niobium concentrate, whose main components and contents are: 32g SiO2, 32g CaO, 21.0g CaF2, 8g Nb2O5, 8g TiO2, 6g Fe2O3 and 5g other minerals, dry it at 240°C for 35h in an argon atmosphere, and then grind it in an agate mortar to obtain an electrolyte.

[0069] An iron rod with a diameter of 6 mm (purity of 99.9%) was polished with sandpaper of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh in turn, then immersed in dilute hydrochloric acid (mass concentration of 10%) for 2 h, and finally ultrasonically cleaned with anhydrous ethanol for 80 min (ultrasonic frequency of 350 W) to remove organic matter on the electrode surface.

[0070] The pretreated tungsten wire was used as the cathode and the graphite electrode was used as the anode, and the area ratio of the anode to the cathode was 6:1.

[0071] The electrolyte was transferred to a boron nitride crucible and placed in an electrolysis device. In an argon atmosphere, the heating furnace was heated to 1350°C at a heating rate of 4°C / min. The electrolyte melt was kept at 1350°C for 120 minutes. After the end of the heat preservation, a 3.0A / cm 2 The electrolyte melt was electrolyzed at 1350°C for 1 hour with a cathode current. After the electrolysis, the melt was slowly cooled with the furnace. After the temperature dropped to room temperature, the solidified electrolyte in the boron nitride crucible was taken out to obtain niobium-iron alloy at the bottom of the electrolyte.

[0072] The SEM-EDS image of the ferroniobium alloy prepared in this embodiment is as follows: Figure 7 As shown, EDS analysis shows that the obtained ferroniobium alloy is FeNb alloy.

[0073] As can be seen from the above embodiments, the present invention provides a method for preparing ferroniobium alloy by electrolysis of niobium concentrate, wherein the niobium concentrate is first dried under a protective atmosphere to obtain an electrolyte; wherein the main components of the niobium concentrate are silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and ferric oxide; and then the electrolyte is electrolyzed to obtain ferroniobium alloy. The present invention uses niobium concentrate after rare earth extraction and efficient iron removal as raw material, adopts a molten oxide-fluoride system for electrolysis to prepare ferroniobium alloy, and can obtain high-quality ferroniobium alloy by effectively controlling the electrolysis process.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing ferroniobium alloy by electrolysis of niobium concentrate, characterized in that: The steps include: (1) Drying the niobium concentrate under a protective atmosphere to obtain an electrolyte; The main components of the niobium concentrate are silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and iron trioxide; (2) Electrolyzing the electrolyte to obtain niobium-iron alloy.

2. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 1, characterized in that: In the step (1), the mass ratio of silicon dioxide, calcium oxide, calcium fluoride, niobium pentoxide, titanium dioxide and ferric oxide is 20-40:20-40:10-30:5-15:5-20:2-10; and the niobium concentrate is Bayan Obo niobium concentrate.

3. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 1 or 2, characterized in that: In the step (1), the drying temperature is 100 to 500° C. and the drying time is 2 to 60 hours.

4. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 3, characterized in that: In the step (1), the protective atmosphere is an argon atmosphere or a nitrogen atmosphere.

5. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 1, 2 or 4, characterized in that: In the step (2), the electrolysis temperature is 1200-1700° C., the electrolysis time is 1-48 hours, and the heating rate to the electrolysis temperature is 3-6° C. / min.

6. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 5, characterized in that: In the step (2), the electrolyte is heated to the electrolysis temperature, and the obtained electrolyte melt is subjected to a heat preservation treatment at the electrolysis temperature before being electrolyzed, wherein the heat preservation treatment time is 30 to 240 minutes.

7. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 4 or 6, characterized in that: In the step (2), during electrolysis, a tungsten wire or an iron rod is used as a cathode, and an inert electrode is used as an anode; the area ratio of the anode to the cathode is 4 to 8:

1.

8. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 7, characterized in that: The diameter of the iron rod is 1-6 mm; the diameter of the tungsten wire is 1-3 mm; the inert electrode is a graphite electrode, a glassy carbon electrode, a platinum electrode, a platinum-rhodium electrode or an iridium electrode.

9. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 8, characterized in that: The method for pre-treating the tungsten wire or the iron rod is: grinding and polishing, acid soaking, and ultrasonic cleaning the tungsten wire or the iron rod in sequence.

10. The method for preparing ferroniobium alloy by electrolysis of niobium concentrate according to claim 6 or 9, characterized in that: The current density of the electrolysis is 0.1 to 3.0 A / cm 2 .

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