Low-grade high-silicon niobium concentrate sulfuric acid smelting method

Abstract

The application provides a low-grade high-silicon type niobium concentrate sulfuric acid smelting method and belongs to the field of niobium metallurgy. The application uses an activator, concentrated sulfuric acid and low-temperature roasting to convert niobium minerals into water-soluble salts and convert rare earth minerals into water-insoluble double salts. After roasting, the minerals are water-immersed to separate niobium from rare earth, silicates and other insoluble impurities. The niobium leaching solution is treated by a small amount of HF to remove impurities, and then is treated by TBP extraction, back extraction and heat treatment to obtain a niobium oxide product with a purity of more than 99%. The rare earth-containing filter residue can be treated by an alkali solution to obtain a rare earth hydroxide, and then is treated by hydrochloric acid leaching, extraction and carbon precipitation process to obtain a rare earth carbonate product. The application solves the problems of low niobium leaching rate of Baotou low-grade high-silicon type niobium concentrate and industrialization of sulfuric acid smelting, and has the advantages of simple process, high element yield, low production cost, energy saving and emission reduction.

Description

Technical Field

[0001] This invention belongs to the field of niobium metallurgy technology, and particularly relates to a method for smelting low-grade, high-silicon niobium concentrate with sulfuric acid. Background Technology

[0002] Niobium is widely used in cutting-edge and high-tech fields such as metallurgy, aerospace, and superconducting materials. Globally, 79% of niobium resources are used to produce high-strength low-alloy steel, with stainless steel, corrosion-resistant and heat-resistant steel accounting for 10% of niobium consumption, and super niobium-based heat-resistant alloys accounting for 9%. Niobium and titanium are important microalloying elements for improving the strength and toughness of steel materials. High-strength low-alloy structural steel with niobium and titanium as the main microalloying elements is the main product of domestic steel companies. Currently, the domestic steel raw material market is facing a severe situation, with ferroniobium and ferrotitanium used in high-strength low-alloy steel mainly relying on imports. Domestic niobium consumption has been continuously increasing, from 3,500 tons in 2004 to over 20,000 tons in 2013, and is projected to reach 23,500-33,600 tons by 2030. Although my country has abundant niobium reserves, it still heavily relies on imports, with an external dependence rate exceeding 95%. my country's niobium resources are mostly low-grade, complexly distributed, and difficult to decompose, making resource utilization challenging. At the same time, the uneven distribution of global niobium resources has resulted in a highly monopolized niobium market, with prices determined by foreign industry giants. Therefore, in order to solve the problem of niobium resource extraction in my country and ensure the safe supply of niobium resources, efficient niobium extraction technology has received widespread attention.

[0003] The Bayan Obo mine is a world-renowned associated mineral deposit rich in strategic resources such as rare earth elements, iron, niobium, scandium, and thorium. my country's niobium oxide reserves in Bayan Obo exceed 6.6 million tons, second only to Brazil, ranking second in the world. However, due to its low grade, fine crystal size, and complex mineral composition, niobium resource recovery has remained at the laboratory stage. my country faces a relative shortage of rich mineral resources, while the rapid development of the national economy has created a large demand for mineral resources. Therefore, developing new methods and key technologies for the efficient and synergistic utilization of niobium resources, tailored to the characteristics of Bayan Obo niobium minerals, and conducting stable pilot-scale production verification to achieve clean, efficient, and scientific utilization of niobium mineral resources is a very urgent task.

[0004] Currently, the main smelting process for niobium minerals worldwide involves adding 50%-60% high-grade niobium minerals into a reactor lined with lead, molybdenum-nickel alloy, or graphite plates. Niobium is then leached in HF (hydrofluoric acid) or HF-H₂SO₄ solutions, resulting in niobium existing as a complex acid (generally using 60-70% hydrofluoric acid at a decomposition temperature of 90-100℃ for 4 hours; the leachate is then cooled, filtered, and sent to the extraction process; the extractant used is methyl ethyl ketone or 2-octanol, etc.). The niobium minerals in Bayan Obo have a complex composition, fine grain size, low grade, and poor selectivity in each mineral phase, exhibiting characteristics of "abundance, scarcity, fineness, and complexity," making it difficult to obtain high-grade niobium concentrate (generally only 1%-5%). This results in significant challenges in mineral processing and smelting. Therefore, niobium is not effectively utilized in existing processes, and large amounts of niobium resources are discharged into tailings ponds, causing serious environmental pollution and resource waste. Currently, although there are processes for smelting dolomite niobium concentrate using HF-H2SO4 or HF, the silica content in the concentrate exceeds 30%, leading to the formation of fluorosilicic acid and silicon tetrafluoride from HF and SiO2. This not only consumes hydrofluoric acid but also results in a high concentration of fluorine-containing substances in the leachate, severely impacting subsequent extraction processes and drastically reducing the extractant's extraction capacity. Furthermore, the back-extraction product contains a significant amount of silicon impurities, making it impractical at present. Given the drawbacks of the hydrofluoric acid process, researchers have developed a high-temperature roasting activation-sulfuric acid leaching process. However, the niobium leaching rate remains low (less than 80%), mostly between 50-60%, and the high-temperature roasting consumes a large amount of energy, increasing costs.

[0005] Therefore, there is an urgent need to develop an effective smelting technology for low-grade, high-silicon niobium concentrate to solve the problems of low niobium yield, high energy consumption, high acid consumption, large amount of waste, and inability to industrialize the current smelting of Bayan Obo niobium concentrate, and to ensure the safe supply of niobium resources. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for smelting low-grade, high-silicon niobium concentrate with sulfuric acid.

[0007] To achieve the above objectives, the present invention provides a method for sulfuric acid smelting of low-grade high-silicon niobium concentrate, wherein an activator, concentrated sulfuric acid and low-grade high-silicon niobium concentrate are first mixed and roasted, and then subjected to subsequent leaching treatment.

[0008] The activator is sodium chloride (NaCl).

[0009] This invention first mixes an activator, concentrated sulfuric acid (concentrated H2SO4), and low-grade, high-silica niobium concentrate. After roasting, it undergoes subsequent conventional treatments such as water leaching. During the roasting process, the activator, concentrated sulfuric acid, and low-grade, high-silica niobium concentrate react with homogeneous niobium minerals (minerals formed by rare earth elements, niobium, and titanium) with hydrochloric acid, sodium sulfate (generated from concentrated sulfuric acid and NaCl), and sulfuric acid to produce water-soluble niobium oxysulfate, niobium chloride, titanium sulfate, titanium chloride, and water-insoluble rare earth sulfate double salts, which precipitate out. This promotes the decomposition of niobium minerals and reduces the Gibbs free energy of niobium mineral decomposition. The addition of the activator NaCl in this invention transforms reactions that would otherwise not occur under low-temperature roasting conditions with concentrated sulfuric acid into decomposition reactions, significantly increasing the niobium leaching rate.

[0010] The method of this invention comprehensively recovers niobium and rare earth elements, with a niobium leaching rate of over 90% and a niobium oxide product purity of over 99%. The method of this invention features a short process flow, high element recovery rate, and low production cost, while significantly reducing the amount of waste and solving the problems of low niobium leaching rate, large acid consumption, and long process flow in existing technologies.

[0011] Furthermore, the method for smelting low-grade, high-silica niobium concentrate with sulfuric acid includes the following steps:

[0012] The activator, concentrated sulfuric acid, and low-grade, high-silica niobium concentrate are mixed and roasted.

[0013] The roasted product was immediately soaked in water.

[0014] The leached solution is filtered to obtain a leachate and a filter residue. The leachate is a niobium-containing leachate, and the filter residue is a filter residue containing silicon minerals and rare earth complex salts.

[0015] The filter residue is treated with an alkaline solution to separate rare earth elements from impurities.

[0016] The leachate was subjected to impurity removal, extraction, washing, back-extraction and heat treatment to obtain niobium oxide (Nb2O5);

[0017] The activator is NaCl.

[0018] Furthermore, the particle size of the low-grade, high-silica niobium concentrate is less than 200 mesh; and / or, the particle size of the activator is less than 200 mesh. The low-grade, high-silica niobium concentrate is crushed and ground to a particle size of less than 200 mesh; the activator NaCl is directly ground to a particle size of less than 200 mesh. This particle size increases the reaction contact area and optimizes heat transfer and reaction uniformity.

[0019] Furthermore, the amount of activator added is 20-30% of the mass of low-grade, high-silica niobium concentrate.

[0020] Furthermore, the calcination temperature is 250-400℃, and the holding time is 1-3 hours.

[0021] Furthermore, the concentrated sulfuric acid is 98 wt% sulfuric acid; the liquid-to-solid ratio of the concentrated sulfuric acid to the low-grade, high-silica niobium concentrate is (0.5-1) L: 1 kg.

[0022] Furthermore, the liquid-to-solid ratio during water immersion is (5-10) L: 1 kg;

[0023] And / or, the immersion time is 2 hours.

[0024] Furthermore, the water immersion is carried out under stirring conditions, and the stirring rate is 200 r / min.

[0025] Furthermore, the alkaline solution is a sodium hydroxide solution.

[0026] Treating filter residue with alkaline solution to obtain rare earth products is a common rare earth recovery method in the field. In this invention, the method for rare earth recovery is not limited, as long as it can achieve rare earth recovery. For example, the steps for treating the filter residue with alkaline solution to separate rare earth from impurities are as follows: A 50% sodium hydroxide solution is added to the filter residue, and the residue is leached at 160°C for 2 hours at a liquid-to-solid ratio of 5:1, causing the rare earth minerals to transform into rare earth hydroxide, while most of the silicon is converted into sodium silicate and enters the solution. After filtration, a rare earth hydroxide filter cake is obtained. The filter cake is then leached with hydrochloric acid to obtain a rare earth chloride solution (a small amount of silicon-containing material remains in the filter residue). The rare earth chloride solution is then extracted and carbonized to obtain rare earth carbonate products.

[0027] When the filter residue is treated with alkaline solution, it is converted into rare earth hydroxide precipitate by the action of hot alkaline solution, while the silicon-containing minerals dissolve in the alkaline solution, thus achieving the separation of rare earth and impurities.

[0028] For example, the steps to obtain niobium oxide after impurity removal, extraction, washing and heat treatment of the leachate are as follows: after adding hydrofluoric acid to the leachate for impurity removal, it is extracted with BTP (tributyl phosphate), and after washing and heat treatment (temperature of 800℃, time of 2-3h), a pure niobium oxide product (purity of niobium oxide is above 99%) is obtained.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] This invention provides a sulfuric acid smelting method for low-grade, high-silica niobium concentrate. It is a short-process smelting method for the comprehensive recovery of niobium and rare earth elements. This invention uses an activator, concentrated sulfuric acid, and low-temperature roasting to convert niobium minerals into water-soluble salts and rare earth minerals into water-insoluble complex salts. On the one hand, it effectively solves the problems of low leaching rate and high acid consumption of niobium minerals in sulfuric acid systems. On the other hand, it effectively solves the problem that rare earth elements in the concentrate are easily soluble in the leachate, difficult to separate, and are extracted into the organic phase along with niobium in subsequent processes, affecting the final purity of the product.

[0031] Compared to existing production processes (HF method, HF-H2SO4 method), the process of this invention achieves hydrofluoric acid-free leaching, improves equipment corrosion and the smelting environment, and significantly reduces production costs. Furthermore, current hydrofluoric acid methods (HF, HF-H2SO4) for treating low-grade silicon-containing niobium concentrates result in leachates containing large amounts of silicon-containing minerals, severely impacting subsequent extraction processes and the purity of the extracted product. In contrast, this invention does not dissolve quartz and silicon-containing minerals during leaching, resulting in relatively fewer impurities in the leachate and no silicon-containing substances affecting extraction, leading to a higher purity product. Compared to existing concentrated sulfuric acid leaching processes, this invention significantly improves the niobium leaching rate, significantly reduces the amount of concentrated sulfuric acid used, and effectively separates niobium from rare earth elements, reducing subsequent processing steps, improving product purity, and solving the problem of the current inability to industrialize sulfuric acid leaching of niobium.

[0032] This invention significantly reduces the amount of acid used and the amount of waste requiring treatment. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to 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. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0037] An embodiment of the present invention provides a method for smelting sulfuric acid from low-grade, high-silica niobium concentrate, comprising the following steps:

[0038] The activator NaCl and concentrated sulfuric acid are mixed with low-grade, high-silicon niobium concentrate and then roasted.

[0039] The roasted product was immediately soaked in water.

[0040] The leached solution is filtered to obtain a leachate and a filter residue. The leachate is a niobium-containing leachate, and the filter residue is a filter residue containing silicon minerals and rare earth complex salts.

[0041] Alkaline solution is used to treat the filter residue to achieve the separation of rare earth elements from impurities;

[0042] Niobium oxide is obtained from the leachate after impurity removal, extraction, washing, back-extraction and heat treatment.

[0043] The method of this invention comprehensively recovers niobium and rare earth elements, with a niobium leaching rate of over 90% and a niobium oxide product purity of over 99%. The method of this invention features a short process flow, high element recovery rate, and low production cost, while significantly reducing the amount of waste and solving the problems of low niobium leaching rate, large acid consumption, and long process flow in existing technologies.

[0044] In embodiments of the present invention, the particle size of the low-grade, high-silica niobium concentrate is less than 200 mesh; and / or, the particle size of the activator is less than 200 mesh. The low-grade, high-silica niobium concentrate is crushed and ground to a particle size less than 200 mesh; the activator NaCl is directly ground to a particle size less than 200 mesh. This particle size increases the reaction contact area and optimizes heat transfer and reaction uniformity. The temperature distribution within the roasting equipment (such as a rotary kiln) is affected by the material's packing state. This particle size can eliminate the "cold center" effect: when coarse particles are packed, a low-temperature zone (cold center) easily forms inside, leading to incomplete local reactions. Fine particles (<200 mesh) have higher porosity (approximately 40% vs. 30% of coarse particles), resulting in more uniform heat penetration. Simultaneously, this particle size can also increase equipment stability: fine particles have high fluidity, reducing the risk of local blockage in the roasting equipment (such as a rotary kiln) and extending equipment life.

[0045] In embodiments of the present invention, the amount of activator added is 20-30% of the mass of low-grade, high-silica niobium concentrate.

[0046] In an embodiment of the present invention, the roasting temperature is 250-400℃ and the holding time is 1-3h to ensure complete decomposition of niobium and rare earth ores.

[0047] In the embodiments of the present invention, the concentrated sulfuric acid is sulfuric acid with a concentration of 98 wt%; the liquid-solid ratio of the concentrated sulfuric acid to the low-grade high-silica niobium concentrate is (0.5-1) L: 1 kg.

[0048] In an embodiment of the present invention, the liquid-to-solid ratio during water immersion is (5-10) L:1 kg; the immersion time is 2 h; the immersion is carried out under stirring conditions, and the stirring rate is 200 r / min. The present invention immediately immerses the calcined product in water. Because the calcined product has a certain temperature, the water temperature will reach 40-60℃.

[0049] The product obtained by roasting a mixture of activator NaCl, concentrated sulfuric acid, and low-grade high-silicon niobium concentrate is then leached with water. The leaching solution is filtered to obtain a niobium-containing leachate and a filter residue containing silicon minerals and rare earth complex salts. High-grade niobium oxide can be obtained by treating the niobium-containing leachate using common processing techniques in the art; the rare earths and impurities can be separated by treating the filter residue containing silicon minerals and rare earth complex salts using common processing techniques in the art. In an embodiment of the present invention, the step of treating the filter residue with an alkaline solution to achieve the separation of rare earths and impurities is as follows: the filter residue is added to a 50% sodium hydroxide solution and leached at 160°C for 2 hours at a liquid-to-solid ratio of 5:1, causing the rare earth minerals to become rare earth hydroxide, while most of the silicon becomes sodium silicate and enters the solution. After filtration, a rare earth hydroxide filter cake is obtained. The filter cake is then leached with hydrochloric acid to obtain a rare earth chloride solution (the remaining small amount of silicon-containing material is completely immersed in the filter residue). The rare earth chloride solution is then subjected to extraction and carbon precipitation processes to obtain rare earth carbonate products. When the filter residue is treated with alkaline solution, it is converted into rare earth hydroxide precipitate by the action of hot alkaline solution, while the silicon-containing minerals dissolve in the alkaline solution, thus achieving the separation of rare earth elements from impurities. The steps for obtaining niobium oxide from the leachate after impurity removal, extraction, washing, back-extraction, and heat treatment are as follows: Hydrofluoric acid is added to the leachate for impurity removal, followed by extraction with BTP (tributyl phosphate), washing, ammonia back-extraction, and heat treatment (at 800℃ for 2-3 hours) to obtain a pure niobium oxide product (purity of niobium oxide is above 99%).

[0050] This invention provides a method for sulfuric acid smelting of low-grade, high-silicon niobium concentrate. It is a short-process smelting method for effectively recovering niobium and rare earth elements. In this invention, niobium concentrate, NaCl, and concentrated H₂SO₄ are mixed and added to a rotary kiln, where they are roasted at 250-400℃ for 1.5-3 hours. After roasting, the niobium minerals are converted into water-soluble salts, while the rare earth elements are converted into water-insoluble complex salts. This process effectively solves the problems of low niobium leaching rate and easy entry of rare earth elements and silicon into the solution when using sulfuric acid to treat Baotou niobium concentrate. The niobium leaching solution produced by this invention has fewer impurities, and only a small amount of hydrofluoric acid (typically around 2 mol / L in the leaching solution) needs to be added in the subsequent step to remove impurities. After extraction and heat treatment, high-grade Nb₂O₅ products can be prepared. At the same time, it avoids the problems of high acid consumption and difficult wastewater treatment in current sulfuric acid leaching methods. Overall, this invention effectively avoids the problems of high acid consumption, silicon entering the leaching solution, and difficulty in extracting niobium in existing processes (HF method, HF-H2SO4 method), while solving the problems of low niobium leaching rate, difficulty in effectively separating rare earth elements, high sulfuric acid consumption, and large amount of waste in the current sulfuric acid method.

[0051] In the following embodiments and comparative examples of the present invention, the testing methods are as follows:

[0052] The contents of REO and Nb2O5 were determined by inductively coupled plasma spectroscopy.

[0053] The leaching rate (%) of niobium and the rare earth loss rate (%) were calculated according to formulas (1) and (2):

[0054]

[0055] In formulas (1) and (2): w 0REO with w 0Nb2O5 , respectively, represent the rare earth and niobium content in the niobium concentrate, in wt%; m0 represents the mass of the niobium concentrate, in kg; w 1REO with w 1Nb2O5 The values ​​are the rare earth and niobium contents in the leaching residue after water immersion, respectively, in wt%; m1 is the mass of the leaching residue after water immersion, in kg.

[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0057] Concentrated sulfuric acid typically refers to sulfuric acid with a mass concentration of 90% or higher. In the embodiments and comparative examples of this invention, "98% sulfuric acid" refers to sulfuric acid with a mass concentration of 98%, which is a colorless, transparent, oily liquid with a density of 1.84 g / cm³. 3 It has a boiling point of 338℃ and is highly corrosive. This sulfuric acid is highly concentrated and has strong oxidizing, dehydrating, and hygroscopic properties.

[0058] In this invention, the unit for liquid-to-solid ratio is L:kg.

[0059] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0060] The technical solution of the present invention will be further illustrated by the following embodiments.

[0061] Example 1

[0062] The chemical composition (mass percentage) of the low-grade, high-silica niobium concentrate used in this embodiment is as follows: Nb₂O₅: 5.65%, REO: 5.58%, ΣFe: 19.78%, SiO₂: 38.74%, TiO₂: 9.48%, CaO: 2.77%, MgO: 2.55%, Al₂O₃: 1.47%, MnO: 1.07%, and others: 12.91%.

[0063] The smelting methods for the above-mentioned low-grade, high-silicon niobium concentrate are as follows:

[0064] A. Raw material preparation: Crush and grind the low-grade high-silicon niobium concentrate to a particle size of less than 200 mesh; grind the activator NaCl to a particle size of less than 200 mesh, add NaCl at 25% of the weight of the low-grade high-silicon niobium concentrate for batching, mix evenly, and then add 98 sulfuric acid with a liquid-to-solid ratio of 0.7:1 (L:kg, the same below) to the evenly mixed material and mix evenly. That is, the acid-to-ore ratio for roasting in this embodiment is 0.7:1.

[0065] B. Low-temperature roasting: Place the evenly mixed material into a rotary kiln, heat it to 340℃, and keep it at that temperature for 2 hours to allow the niobium mineral and rare earth mineral to react fully.

[0066] C. Water leaching: The material after low-temperature roasting is immediately added to the water-containing leaching tank at a liquid-to-solid ratio of 8:1 (L:kg, the same below) and leached for 2 hours at a stirring rate of 200r / min to leach niobium minerals. That is, the liquid-to-solid ratio of leaching in this embodiment is 8:1.

[0067] D. After leaching, filter to obtain leachate and filter residue. Wash the filter residue. The leachate is niobium-containing leachate, and the filter residue is filter residue containing silicon minerals and rare earth complex salts.

[0068] E. Add a 50% sodium hydroxide solution to the filter residue and leach it at 160℃ for 2 hours with a liquid-to-solid ratio of 5:1. Under the action of the hot alkaline solution, the rare earth minerals are converted into rare earth hydroxides, while most of the silicon is converted into sodium silicate and enters the solution. After filtration, a rare earth hydroxide filter cake is obtained. The rare earth hydroxide filter cake is then leached with hydrochloric acid (6 mol / L) to obtain a rare earth chloride solution (a small amount of silicon-containing substances remain in the filter residue). The rare earth chloride solution is extracted (extractant P507 at room temperature) and carbonized (ammonium carbonate at room temperature) to obtain a rare earth carbonate product, thus achieving the separation of rare earth and impurities. After adding a small amount of hydrofluoric acid (the concentration of hydrofluoric acid in the leaching solution is 2 mol / L) to remove impurities, the leachate obtained in step D is extracted with BTP, washed, back-extracted with ammonia, and heat-treated at 800℃ for 2 hours to obtain a pure niobium oxide product.

[0069] The niobium concentrate was subjected to low-temperature roasting and water leaching, with a niobium leaching rate of 91.01% and a rare earth loss rate of 5.21%. In this example, the purity of niobium oxide was 99.01%, as detailed in Table 1.

[0070] Comparative Example 1

[0071] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is that the activator NaCl was not added. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product niobium oxide are shown in Table 1.

[0072] Comparative Example 2

[0073] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the amount of NaCl added as the activator. See Table 1 for details. The niobium leaching rate, rare earth loss rate, and purity of the final product, niobium oxide, are shown in Table 1.

[0074] Comparative Example 3

[0075] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the amount of NaCl added as the activator. See Table 1 for details. The niobium leaching rate, rare earth loss rate, and purity of the final product, niobium oxide, are shown in Table 1.

[0076] Comparative Example 4

[0077] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the low-temperature roasting temperature, as shown in Table 1. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product, niobium oxide, are shown in Table 1.

[0078] Comparative Example 5

[0079] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the low-temperature roasting temperature, as shown in Table 1. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product, niobium oxide, are shown in Table 1.

[0080] Comparative Example 6

[0081] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the low-temperature roasting time, as shown in Table 1. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product, niobium oxide, are shown in Table 1.

[0082] Comparative Example 7

[0083] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the sulfuric acid concentration, as shown in Table 1. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product, niobium oxide, are shown in Table 1.

[0084] Comparative Example 8

[0085] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the acid-ore ratio during roasting, as shown in Table 1. The niobium leaching rate, rare earth loss rate, and purity of the final product, niobium oxide, are shown in Table 1.

[0086] Comparative Example 9

[0087] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the liquid-to-solid ratio of the leaching process, as shown in Table 1. The leaching rate of niobium, the loss rate of rare earth elements, and the purity of the final product, niobium oxide, are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] As can be seen from the data in Table 1:

[0092] A comparison of Example 1 and Comparative Example 1 shows that without the addition of NaCl particles as an activator, the niobium leaching rate of the niobium concentrate is low, the amount of rare earth dissolved in the leachate is large, and the loss rate of rare earth in the slag is relatively large. This is mainly because the niobium minerals in the niobium concentrate do not react completely. In addition, the rare earth sulfate generated in the leachate does not form a double salt precipitate because it does not contain sodium. A large amount of rare earth enters the leachate during leaching, and the niobium-containing leachate fails to completely remove the rare earth during the impurity removal process. TBP can extract rare earth, which leads to a decrease in the purity of the subsequent niobium oxide product.

[0093] A comparison of Example 1 and Comparative Example 2 shows that when the amount of activator added is small, the niobium minerals in the concentrate do not react completely during roasting, the niobium yield (i.e., the niobium leaching rate) is less than 90%, and the insufficient sodium content leads to the loss of rare earth elements. The leachate contains a large amount of rare earth elements, which causes problems in subsequent impurity removal and extraction, and the purity of the niobium oxide product does not reach more than 99%.

[0094] A comparison of Example 1 and Comparative Example 3 shows that when too much activator is added, it is actually detrimental to the leaching of niobium.

[0095] A comparison of Example 1 and Comparative Example 4 shows that when the roasting temperature is low, the decomposition of minerals such as niobium and rare earth elements is incomplete, resulting in a low niobium leaching rate.

[0096] A comparison of Example 1 and Comparative Example 5 shows that when the calcination temperature is high, the generated niobium is easily burned out, reducing its activity and making it difficult to leach.

[0097] A comparison of Example 1 and Comparative Example 6 shows that when the roasting time is short, the niobium mineral is not completely decomposed, resulting in a low niobium leaching rate.

[0098] A comparison of Example 1 and Comparative Example 7 shows that when the concentration of sulfuric acid during roasting is low, the sulfuric acid decomposes the niobium minerals less completely, resulting in a lower niobium leaching rate.

[0099] A comparison of Example 1 and Comparative Example 8 shows that when the acid content of the roasted ore is low, the sulfuric acid does not come into sufficient contact with the mineral, and the niobium mineral is not completely decomposed, resulting in a low niobium leaching rate.

[0100] A comparison of Example 1 and Comparative Example 9 shows that when the liquid-to-solid ratio of the leaching is low, the roasted ore does not come into sufficient contact with water, resulting in poor leaching kinetics and hindering the leaching and dissolution of niobium.

[0101] Therefore, based on the above comparison, it can be seen that there is an optimal range for the parameters in the process. Exceeding this range will correspondingly reduce the element yield and product purity.

[0102] Comparative Example 10

[0103] The chemical composition and smelting method of the low-grade, high-silicon niobium concentrate used in this comparative example are the same as those in Example 1. The only difference is the activator, which is potassium chloride in this comparative example.

[0104] In this comparative example, the leaching rate of niobium was 75.05%, the loss rate of rare earth elements was 6.09%, and the purity of niobium oxide was 95.02%.

[0105] Comparative Example 11

[0106] The chemical composition of the low-grade, high-silicon niobium concentrate used in this comparative example is the same as that in Example 1, and the smelting method is the same as that in Example 1. The only difference is the activator, which is ammonium chloride in this comparative example.

[0107] In this comparative example, the leaching rate of niobium was 72.42%, the loss rate of rare earth elements was 65.49%, and the purity of niobium oxide was 96.14%.

[0108] Comparative Example 12

[0109] The chemical composition and smelting method of the low-grade, high-silica niobium concentrate used in this comparative example are the same as those in Example 1. The only difference is the activator, which is hydrochloric acid.

[0110] In this comparative example, the leaching rate of niobium was 79.05%, the loss rate of rare earth elements was 67.91%, and the purity of niobium oxide was 94.68%.

[0111] Comparative Example 13

[0112] The chemical composition and smelting method of the low-grade, high-silicon niobium concentrate used in this comparative example are the same as those in Example 1. The only difference is the activator, which is Ca2SO4 in this comparative example.

[0113] In this comparative example, the leaching rate of niobium was 69.14%, the loss rate of rare earth elements was 60.25%, and the purity of niobium oxide was 95.17%.

[0114] As shown in Example 1 and Comparative Examples 10-13, the type of activator affects the leaching rate of niobium, the loss rate of rare earth elements, and the purity of niobium oxide.

[0115] Comparative Example 14

[0116] The low-grade, high-silica niobium concentrate used in this comparative example has the same chemical composition as in Example 1, and the smelting method is as follows:

[0117] A. Raw material preparation: Crush and grind the low-grade high-silicon niobium concentrate to a particle size of less than 200 mesh; grind the activator NaCl to a particle size of less than 200 mesh, add NaCl at 25% of the weight of the low-grade high-silicon niobium concentrate for batching, and mix evenly;

[0118] B. Low-temperature roasting: Place the evenly mixed material into a rotary kiln, heat it to 340℃, and keep it at that temperature for 2 hours to allow the niobium mineral and rare earth mineral to react fully.

[0119] C. Acid leaching: Add 98% sulfuric acid with a liquid-to-solid ratio of 0.7:1 to the product after low-temperature roasting and mix thoroughly;

[0120] D. Water leaching: The material after low-temperature roasting is leached in a leaching tank for 2 hours at a liquid-to-solid ratio of 8:1 and a stirring rate of 200 r / min to leach niobium minerals.

[0121] In this comparative example, the leaching rate of niobium was 5.04%, and the loss rate of rare earth elements was 4.12%. This is mainly because the niobium minerals were roasted in this comparative example without concentrated sulfuric acid, resulting in almost no decomposition of the niobium minerals, which meant that concentrated sulfuric acid could not decompose the niobium minerals at room temperature.

[0122] Example 2

[0123] The low-grade, high-silica niobium concentrate (hereinafter referred to as niobium concentrate) used in this embodiment has the same chemical composition as in Example 1, and the smelting method is as follows:

[0124] A. Raw material preparation: Crush and grind the niobium concentrate to a particle size of less than 200 mesh; grind the activator NaCl to a particle size of less than 200 mesh, add NaCl at 22% of the weight of the niobium concentrate for batching, mix evenly, and then add 98% concentrated sulfuric acid with a liquid-to-solid ratio of 0.6:1 to the evenly mixed material and mix evenly.

[0125] B. Low-temperature roasting: The uniformly mixed furnace charge is placed into a rotary kiln, heated to 380℃, and held for 2 hours to allow the niobium minerals and rare earth minerals to react fully.

[0126] C. Water leaching: At a liquid-to-solid ratio of 6:1, the material after low-temperature roasting is immediately added to a water-containing leaching tank and leached for 2 hours at a stirring rate of 200 r / min to leach niobium minerals.

[0127] D. After leaching, filter to obtain leachate and filter residue. Wash the filter residue. The leachate is niobium-containing leachate, and the filter residue is filter residue containing silicon minerals and rare earth complex salts.

[0128] E. Same as Example 1.

[0129] In this embodiment, the leaching rate of niobium was 91.07%, the loss rate of rare earth elements was 4.91%, and the purity of niobium oxide was 99.06%.

[0130] Example 3

[0131] The chemical composition (mass percentage) of the low-grade, high-silica niobium concentrate (hereinafter referred to as niobium concentrate) used in this embodiment is as follows: Nb2O5: 14.59%, REO: 14.66%, ΣFe: 16.42%, SiO2: 26.33%, TiO2: 10.20%, CaO: 3.31%, MgO: 3.27%, Al2O3: 1.75%, MnO: 1.74%, and others: 7.73%.

[0132] The smelting method is as follows:

[0133] A. Raw material preparation: Grind niobium concentrate to a particle size of less than 200 mesh, grind activator NaCl to a particle size of less than 200 mesh, add NaCl at 30% of the weight of niobium concentrate for batching, mix evenly, and then add 98% concentrated sulfuric acid with a liquid-to-solid ratio of 1:1 to the evenly mixed material and mix evenly.

[0134] B. Low-temperature roasting: The uniformly mixed furnace charge is placed into a rotary kiln, heated to 400℃, and held for 2 hours to allow the niobium minerals and rare earth minerals to react fully.

[0135] C. Water leaching: At a liquid-to-solid ratio of 10:1, the material after low-temperature roasting is immediately added to a water-containing leaching tank and leached for 2 hours at a stirring rate of 200 r / min to leach niobium minerals.

[0136] D. After leaching, filter to obtain leachate and filter residue. Wash the filter residue. The leachate is niobium-containing leachate, and the filter residue is filter residue containing silicon minerals and rare earth complex salts.

[0137] E. Same as Example 1.

[0138] In this embodiment, the leaching rate of niobium was 95.28%, the loss rate of rare earth elements was 4.81%, and the purity of niobium oxide was 99.21%.

[0139] Example 4

[0140] The chemical composition (mass percentage) of the low-grade, high-silica niobium concentrate (hereinafter referred to as niobium concentrate) used in this embodiment is as follows: Nb2O5: 2.08%, REO: 4.62%, ΣFe: 14.80%, SiO2: 42.76%, TiO2: 5.03%, CaO: 6.10%, MgO: 2.34%, Al2O3: 1.06%, MnO: 1.19%, and others: 20.02%.

[0141] The smelting method is as follows:

[0142] A. Raw material preparation: Crush and grind the niobium concentrate to a particle size of less than 200 mesh; grind the activator NaCl to a particle size of less than 200 mesh, add NaCl at 20% of the weight of the niobium concentrate and mix evenly, then add 98% concentrated sulfuric acid with a liquid-to-solid ratio of 0.5:1 to the evenly mixed material and mix evenly.

[0143] B. Low-temperature roasting: The uniformly mixed furnace charge is placed into a rotary kiln, heated to 250°C, and held for 3 hours to allow the niobium minerals and rare earth minerals to react fully.

[0144] C. Water leaching: At a liquid-to-solid ratio of 5:1, the material after low-temperature roasting is immediately added to a water-containing leaching tank and leached for 2 hours at a stirring rate of 200 r / min to leach niobium minerals.

[0145] D. After leaching, filter to obtain leachate and filter residue. Wash the filter residue. The leachate is niobium-containing leachate, and the filter residue is filter residue containing silicon minerals and rare earth complex salts.

[0146] E. Same as Example 1.

[0147] In this embodiment, the leaching rate of niobium is 90.05%, the loss rate of rare earth elements is 6.09%, and the purity of niobium oxide is 99.12%.

[0148] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for smelting low-grade high-silicon niobium concentrate by sulfuric acid, characterized in that, First, the activator, concentrated sulfuric acid and low-grade high-silica niobium concentrate are mixed, roasted, and then subjected to subsequent leaching treatment. The activator is sodium chloride.

2. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 1, characterized in that, Includes the following steps: The activator, concentrated sulfuric acid, and low-grade, high-silica niobium concentrate are mixed and roasted. The roasted product was immediately soaked in water. The leached solution is filtered to obtain a leachate and a filter residue. The leachate is a niobium-containing leachate, and the filter residue is a filter residue containing silicon minerals and rare earth complex salts. The filter residue is treated with an alkaline solution to separate rare earth elements from impurities. The leachate was subjected to impurity removal, extraction, washing, back-extraction and heat treatment to obtain niobium oxide; The activator is sodium chloride.

3. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 2, characterized in that, The low-grade, high-silicon niobium concentrate has a particle size of less than 200 mesh. And / or, the particle size of the activator is less than 200 mesh.

4. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 3, characterized in that, The amount of activator added is 20-30% of the mass of low-grade, high-silica niobium concentrate.

5. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 2, characterized in that, The roasting temperature is 250-400℃, and the holding time is 1-3 hours.

6. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 2, characterized in that, The concentrated sulfuric acid is 98 wt% sulfuric acid; the liquid-solid ratio of the concentrated sulfuric acid to the low-grade high-silica niobium concentrate is (0.5-1) L: 1 kg.

7. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 2, characterized in that, The liquid-to-solid ratio during water immersion is (5-10) L: 1 kg; And / or, the immersion time is 2 hours.

8. The method for smelting low-grade, high-silica niobium concentrate with sulfuric acid according to claim 7, characterized in that, The water immersion is carried out under stirring conditions.

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