Sulfuric acid smelting method for low-grade high-silicon niobium concentrate

Abstract

The invention provides a low-grade high-silicon niobium concentrate sulfuric acid smelting method, and belongs to the field of niobium metallurgy. According to the method disclosed by the invention, niobium minerals are converted into water-soluble salts and rare earth minerals are converted into water-insoluble double salts by adopting an activating agent, concentrated sulfuric acid and low-temperature roasting, and the minerals after roasting are subjected to water leaching, so that separation of niobium from other insoluble impurities such as rare earth and silicate is realized; according to the process, a niobium leaching solution is subjected to impurity removal through a small amount of HF, and then is subjected to TBP extraction, reverse extraction and heat treatment to obtain a niobium oxide product with the purity being 99% or above; the filter residues containing the rare earth can be treated through alkali liquor to obtain rare earth hydroxide, and then the rare earth carbonate product is obtained through hydrochloric acid leaching, extraction and carbon precipitation processes. The method solves the problems that the Baotou low-grade high-silicon niobium concentrate is low in niobium leaching rate and sulfuric acid smelting cannot be industrialized, and has the advantages of being simple in process, high in element yield, low in production cost, energy-saving and emission-reducing.

Description

Technical Field

[0001] The present invention belongs to the technical field of niobium metallurgy, and particularly relates to a sulfuric acid smelting method for low-grade high-silicon niobium concentrate. Background Art

[0002] Niobium is widely used in cutting-edge and high-tech fields such as metallurgy, aerospace, and superconducting materials. 79% of the world's niobium resources are used to produce high-strength low-alloy steel, 10% of niobium is consumed in stainless steel, corrosion-resistant and heat-resistant steel, and 9% is used in super niobium-based heat-resistant alloys. 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 produced by domestic steel enterprises. Currently, the domestic steel raw material market situation is severe, and ferroniobium and ferrotitanium used in high-strength low-alloy steel mainly rely on imports. The domestic consumption of niobium continues to grow, increasing from 3,500t in 2004 to over 20,000t in 2013, and is expected to reach 23,500 - 33,600t in 2030. Although China has rich niobium resources reserves, it still heavily relies on imports, with a foreign dependence degree of over 95%. Most of China's niobium resources are characterized by low grade, complex distribution, and difficult decomposition, making it difficult to utilize the resources. At the same time, the uneven distribution of world niobium resources results in a highly monopolized niobium market, and the price is determined by foreign industry giants. Therefore, in order to solve the problem of extracting niobium resources in China and ensure the safe supply of niobium resources, highly efficient niobium extraction technologies have been widely concerned.

[0003] The Bayan Obo ore is a world-renowned associated ore rich in strategic resources such as rare earth, iron, niobium, scandium, and thorium. The reserves of niobium oxide in China's Bayan Obo ore are more than 6.6 million tons, ranking second in the world after Brazil. However, due to its low grade, fine crystal grain size, and complex mineral composition, the recovery of niobium resources has remained at the laboratory stage. China's rich ore resources are relatively scarce, and the rapid development of the national economy has a large demand for mineral resources. How to develop new methods and key technologies suitable for the efficient collaborative utilization of niobium resources according to the characteristics of Bayan Obo niobium minerals, and conduct stable production verification on the pilot scale, and cleanly, efficiently, and scientifically utilize niobium mineral resources is a very urgent task.

[0004] At present, the main smelting process of niobium minerals in the world is to add 50%-60% high-grade niobium minerals into a reactor lined with lead, molybdenum-nickel alloy or graphite plates. Through HF (hydrofluoric acid) or HF-H2SO4 leaching solution, niobium exists in the form of complex acid (generally using hydrofluoric acid with a mass concentration of 60%-70%, decomposition temperature of 90-100°C, leaching for 4 hours, and the leaching solution is filtered after cooling and sent to the extraction process. The extractant is methyl ethyl butyl ketone or sec-octanol, etc.). The niobium minerals in Bayan Obo are complex in composition, fine in dissemination size, low in grade, poor in stable selectivity of each mineral phase, showing the characteristics of "many, poor, fine, and miscellaneous", and it is difficult to select high-grade niobium concentrate (generally only 1%-5%), resulting in great difficulties in ore dressing and smelting of this ore. Therefore, niobium is not effectively utilized in the existing process, and a large amount of niobium resources are discharged into the tailings pond, causing serious environmental pollution and resource waste. At present, although there is a process for smelting Bayan niobium concentrate through HF-H2SO4 or HF, due to the silicon dioxide content in Bayan niobium concentrate reaching more than 30%, a large amount of HF reacts with SiO2 to form fluosilicic acid and silicon tetrafluoride, which not only consumes hydrofluoric acid, but also makes the leaching solution contain a large amount of fluorine-containing substances, seriously affecting the subsequent extraction process, sharply reducing the extraction ability of the extractant, and having more silicon-containing impurities in the stripping product. Therefore, it cannot be actually applied at present. In view of the disadvantages of the hydrofluoric acid process, researchers have developed a high-temperature roasting activation-sulfuric acid leaching process, but the leaching rate of niobium is still low (less than 80%), and most of them are between 50%-60%. Moreover, high-temperature roasting consumes a large amount of energy, resulting in increased costs.

[0005] Therefore, it is urgent to develop an effective smelting technology for low-grade high-silicon niobium concentrate to solve the problems of low niobium recovery rate, high energy consumption, large acid consumption, large amount of three wastes, and inability to industrialize during the smelting of Bayan Obo niobium concentrate, and ensure the safe supply of niobium resources. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a sulfuric acid smelting method for low-grade high-silicon niobium concentrate.

[0007] To achieve the above object, the present invention provides a sulfuric acid smelting method for low-grade high-silicon niobium concentrate, which first mixes an activator, concentrated sulfuric acid and low-grade high-silicon niobium concentrate, roasts, and then performs subsequent leaching treatment;

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

[0009] In the present invention, an activator, concentrated sulfuric acid (H2SO4), and low-grade high-silicon niobium concentrate are first mixed, and after roasting, subsequent conventional treatments such as water leaching are carried out. During the roasting process of the activator, concentrated sulfuric acid, and low-grade high-silicon niobium concentrate, isomorphous niobium minerals (minerals formed by the isomorphous of rare earth, niobium, and titanium) react with hydrochloric acid, sodium sulfate (formed by concentrated sulfuric acid and NaCl), and sulfuric acid to form niobium oxysulfate, niobium chloride, titanium sulfate, titanium chloride that are soluble in water, and a rare earth sulfate double salt that is insoluble in water and settles, promoting the decomposition of niobium minerals and reducing the Gibbs free energy for decomposing niobium minerals. After adding the activator NaCl in the present invention, under the condition of low-temperature roasting, the reaction that could not originally occur is transformed into a decomposition reaction, greatly improving the leaching rate of niobium elements.

[0010] By using the method of the present invention, niobium and rare earth elements are comprehensively recovered. The leaching rate of niobium elements is above 90%, and the product purity of niobium oxide is above 99%. The method of the present invention has the characteristics of short process flow, high element recovery rate, and low production cost. At the same time, it significantly reduces the amount of three wastes and solves the problems of low niobium leaching rate, large acid consumption, and long process flow in the prior art.

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

[0012] Mix an activator, concentrated sulfuric acid, and low-grade high-silicon niobium concentrate, and roast;

[0013] Immediately carry out water leaching on the roasted product;

[0014] Filter the leached solution 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 double salts;

[0015] Treat the filter residue with an alkali solution to separate rare earths from impurities;

[0016] The leachate is obtained as niobium oxide (Nb2O5) after impurity removal, extraction, washing, back-extraction, and heat treatment;

[0017] The activator is NaCl.

[0018] Furthermore, the particle size of the low-grade high-silicon niobium concentrate is less than 200 mesh; and / or, the particle size of the activator is less than 200 mesh. The low-grade high-silicon niobium concentrate is crushed and ground to make its particle size less than 200 mesh; the activator NaCl is directly ground to make its particle size less than 200 mesh. This particle size can increase the reaction contact area, optimize heat transfer, and reaction uniformity.

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

[0020] Further, the calcination temperature is 250 - 400 °C, and the heat preservation time is 1 - 3 h.

[0021] Further, 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 - silicon niobium concentrate is (0.5 - 1) L∶1 kg.

[0022] Further, the liquid - solid ratio during water leaching is (5 - 10) L∶1 kg;

[0023] and / or, the time for water leaching is 2 h.

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

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

[0026] Using an alkaline solution to treat the filter residue to obtain rare - earth products is a common rare - earth recovery method in the art. In the present invention, the method for recovering rare earths is not limited, as long as rare - earth recovery can be achieved. Exemplarily, the steps for separating rare earths from impurities by using an alkaline solution to treat the filter residue are as follows: adding a sodium hydroxide solution with a mass concentration of 50% to the filter residue, carrying out alkaline leaching at a liquid - solid ratio of 5:1 and 160 °C for 2 h, so that rare - earth minerals become rare - earth hydroxides, and 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 (a small amount of silicon - containing substances remain in the filter residue). The rare - earth chloride solution is obtained through extraction and carbon precipitation to obtain a rare - earth carbonate product.

[0027] When using an alkaline solution to treat the filter residue, the filter residue is converted into rare - earth hydroxide precipitation under the action of hot alkaline solution, while the silicon - containing minerals react with the alkali and dissolve in the alkaline solution, realizing the separation of rare earths from impurities.

[0028] Exemplarily, the steps for obtaining niobium oxide from the leaching solution after impurity removal, extraction, washing, and heat treatment are as follows: adding hydrofluoric acid to the leaching solution for impurity removal, then extracting with BTP (tributyl phosphate), and after washing and heat treatment (temperature is 800 °C, time is 2 - 3 h), a pure niobium oxide product (the 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] The present invention provides a sulfuric acid smelting method for low-grade high-silicon niobium concentrate, which is a short-process smelting method for comprehensively recovering niobium and rare earths. The present invention uses an activator, concentrated sulfuric acid and low-temperature roasting to convert niobium minerals into water-soluble salts, while rare earth minerals are converted into water-insoluble double salts. On the one hand, it effectively solves the problems of low leaching rate and high acid consumption of niobium minerals in the sulfuric acid system; on the other hand, it effectively solves the problem that rare earths in the concentrate are easily soluble in the leaching solution and difficult to separate, and are extracted into the organic phase together with niobium in the subsequent process, affecting the final purity of the product.

[0031] Compared with the existing production processes (HF method, HF-H2SO4 method), the process of the present invention realizes leaching without hydrofluoric acid, improves equipment corrosion and smelting environment, and greatly reduces production costs. In addition, when treating low-grade silicon-containing niobium concentrate by the current hydrofluoric acid method (HF, HF-H2SO4), a large amount of silicon-containing minerals are contained in the leaching solution, which seriously affects the subsequent extraction process and the purity of the product after extraction; while the present invention does not dissolve quartz and silicon-containing minerals during leaching, the leaching solution has relatively few impurities, and there is no silicon-containing substance affecting extraction, and the purity of the product after extraction is relatively high. Compared with the existing concentrated sulfuric acid leaching process, the leaching rate of niobium in the present invention is greatly improved, the dosage of concentrated sulfuric acid is significantly reduced, and niobium and rare earth are effectively separated, reducing the process for subsequent treatment, improving the product purity, and solving the problem that sulfuric acid leaching of niobium cannot be industrialized at present.

[0032] The acid consumption of the present invention is greatly reduced, and the amount of three wastes treatment is reduced. Detailed implementation manners

[0033] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0034] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. In addition, for the numerical ranges in the present 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 the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0035] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one 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 practice 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 said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0036] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0037] Embodiments of this invention provide a sulfuric acid smelting method for low-grade high-silicon niobium concentrate, comprising the following steps:

[0038] Mix an activator NaCl, concentrated sulfuric acid and low-grade high-silicon niobium concentrate, and roast.

[0039] Immediately subject the roasted product to water leaching.

[0040] Filter the leached solution 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 double salts.

[0041] Treat the filter residue with an alkali solution to separate rare earths from impurities.

[0042] The leachate is subjected to impurity removal, extraction, washing, stripping and heat treatment to obtain niobium oxide.

[0043] Using the method of this invention, niobium and rare earth elements are comprehensively recovered. The leaching rate of niobium element is above 90%, and the product purity of niobium oxide is above 99%. The method of this invention has the characteristics of short process flow, high element recovery rate and low production cost. At the same time, the amount of three wastes is significantly reduced, solving the problems of low niobium leaching rate, large acid consumption and long process flow in the prior art.

[0044] In an embodiment of the present invention, the particle size of the low-grade high-silicon niobium concentrate is less than 200 mesh; and / or, the particle size of the activator is less than 200 mesh. The low-grade high-silicon niobium concentrate is crushed and ground to make its particle size less than 200 mesh; the activator NaCl is directly ground to make its particle size less than 200 mesh. This particle size can increase the reaction contact area, optimize heat transfer and reaction uniformity. The temperature distribution in the roasting equipment (such as a rotary kiln) is affected by the material stacking state. This particle size can eliminate the "cold center" effect: when coarse particles are stacked, a low-temperature zone (cold center) is easily formed inside, resulting in incomplete local reactions. The stacking porosity of fine particles (<200 mesh) is higher (about 40% vs. 30% of coarse particles), and heat penetration is more uniform. At the same time, the particles of this particle size can also increase the equipment stability: the fine particles have strong fluidity, reducing the risk of local blockage of the roasting equipment (such as a rotary kiln) and extending the equipment life.

[0045] In an embodiment of the present invention, the addition amount of the activator is 20-30% of the mass of the low-grade high-silicon niobium concentrate.

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

[0047] In an embodiment 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-silicon niobium concentrate is (0.5-1) L∶1 kg.

[0048] In an embodiment of the present invention, the liquid-solid ratio during water leaching is (5-10) L∶1 kg; the water leaching time is 2 h; water leaching is carried out under stirring conditions, and the stirring rate is 200 r / min. In the present invention, the product after roasting is immediately subjected to water leaching. Since the product after roasting has a certain temperature, the temperature of the water will reach 40-60 °C.

[0049] After the product obtained by roasting the mixture of the activator NaCl, concentrated sulfuric acid and low-grade high-silicon niobium concentrate is leached with water, the leaching solution is filtered to obtain a niobium-containing leaching solution and a filter residue containing silicon minerals and rare earth double salts. The niobium-containing leaching solution can be treated by common treatment processes in the art to obtain high-grade niobium oxide; the filter residue containing silicon minerals and rare earth double salts can be treated by common treatment processes in the art to separate rare earths from impurities. In the examples of the present invention, the filter residue is treated with an alkali solution, and the steps for separating rare earths from impurities are as follows: adding the filter residue to a sodium hydroxide solution with a mass concentration of 50%, leaching with alkali at a liquid-solid ratio of 5:1 and 160 °C for 2 h to convert rare earth minerals into rare earth hydroxides, and most of the silicon into sodium silicate and entering the solution. After filtration, a rare earth hydroxide filter cake is obtained. The filter cake is leached with hydrochloric acid to obtain a rare earth chloride solution (the remaining small amount of silicon-containing substances are all immersed in the filter residue). The rare earth chloride solution is obtained through processes such as extraction and carbon precipitation to obtain a rare earth carbonate product. When the filter residue is treated with an alkali solution, the filter residue is converted into rare earth hydroxide precipitate under the action of hot alkali solution, while the silicon-containing minerals react with the alkali and dissolve in the alkali solution, realizing the separation of rare earths from impurities. The steps for obtaining niobium oxide after the leaching solution is subjected to impurity removal, extraction, washing, stripping and heat treatment are as follows: adding hydrofluoric acid to the leaching solution for impurity removal, extracting with BTP (tributyl phosphate), and obtaining a pure niobium oxide product (the purity of niobium oxide is above 99%) after washing, stripping with ammonia water and heat treatment (temperature is 800 °C, time is 2 - 3 h).

[0050] The present invention provides a sulfuric acid smelting method for low-grade high-silicon niobium concentrate, which is a short-process smelting method for effectively recovering niobium and rare earth elements. The present invention mixes niobium concentrate, NaCl and concentrated H2SO4, adds them into a rotary kiln, and roasts at 250 - 400 °C for 1.5 - 3 h. After roasting, niobium minerals are converted into salts easily soluble in water, while rare earths are converted into double salts insoluble in water. This process effectively solves the problems of low niobium leaching rate in the treatment of Baotou niobium concentrate with sulfuric acid and the easy entry of rare earths and silicon into the solution. The niobium-containing leaching solution of the present invention has few impurities, and only a small amount of hydrofluoric acid (usually the concentration of hydrofluoric acid in the leaching solution is about 2 mol / L) needs to be added for impurity removal, and then high-grade Nb2O5 products can be prepared through extraction and heat treatment. At the same time, it also avoids the problems of large consumption of sulfuric acid and difficult wastewater treatment in current sulfuric acid leaching. Generally speaking, the present invention effectively avoids the problems of large consumption of acids, silicon entering the leaching solution, and difficult extraction of niobium in existing processes (HF method, HF-H2SO4 method), and at the same time solves the problems of low niobium leaching rate, difficult effective separation of rare earths, large consumption of sulfuric acid, and large amount of three wastes in current sulfuric acid methods.

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

[0052] The REO content and Nb2O5 content are both determined by inductively coupled plasma spectrometry.

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

[0054]

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

[0056] Regarding "including", "comprising", "having", "containing", etc. used in this text, they are all open-ended terms, meaning including but not limited to.

[0057] Concentrated sulfuric acid usually refers to sulfuric acid with a mass concentration above 90%. The "98 sulfuric acid" in the examples and comparative examples of the present invention refers to sulfuric acid with a mass concentration of 98%. It is a colorless transparent oily liquid with a density of 1.84 g / cm 3 , a boiling point of 338 °C, and strong corrosiveness. This sulfuric acid has a high concentration and has strong oxidizing, dehydrating, and water-absorbing properties.

[0058] In the present invention, the unit of liquid-solid ratio is L∶kg.

[0059] It should be noted that the parts not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0060] The technical solution of the present invention is further described below through examples.

[0061] Example 1

[0062] The chemical composition (mass percentage) of the low-grade high-silicon type niobium concentrate used in this example is: 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%, others: 12.91%.

[0063] The smelting method of the above low-grade high-silicon type niobium concentrate is as follows:

[0064] A. Raw material preparation: Crush the low-grade high-silicon niobium concentrate and grind it to a particle size less than 200 mesh; grind the activator NaCl to a particle size less than 200 mesh, add NaCl according to 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-solid ratio of 0.7:1 (L:kg, the same below) to the evenly mixed material and mix evenly. That is, the acid-ore ratio for roasting in this example is 0.7:1;

[0065] B. Low-temperature roasting: Place the evenly mixed material into a rotary kiln, heat it to 340 °C, and keep it warm for 2 hours to allow the niobium minerals and rare earth minerals to react fully;

[0066] C. Water leaching: Immediately add the material after low-temperature roasting to a water-containing leaching tank according to a liquid-solid ratio of 8:1 (L:kg, the same below), leach for 2 h, and the stirring rate is 200 r / min to leach the niobium minerals. That is, the liquid-solid ratio for leaching in this example is 8:1;

[0067] D. After the leaching is completed, filter to obtain a leaching solution and filter residue, wash the filter residue. The leaching solution is a niobium-containing leaching solution, and the filter residue is a filter residue containing silicon minerals and rare earth double salts;

[0068] E. Add a sodium hydroxide solution with a mass concentration of 50% to the filter residue, carry out alkali leaching at a liquid-solid ratio of 5:1 and 160 °C for 2 h. The rare earth minerals are converted into rare earth hydroxides under the action of hot alkali solution, and most of the silicon becomes 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 subjected to extraction (extraction agent P507 is used for extraction at room temperature) and carbon precipitation (ammonium bicarbonate precipitation at room temperature) to obtain a rare earth carbonate product, realizing the separation of rare earths and impurities; a small amount of hydrofluoric acid (the concentration of hydrofluoric acid in the leaching solution is 2 mol / L) is added to the leaching solution obtained in step D for impurity removal, and then it is subjected to extraction, washing, ammonia stripping, and heat treatment at 800 °C for 2 h with BTP to obtain a pure niobium oxide product.

[0069] After the niobium concentrate undergoes low-temperature roasting - water leaching, the leaching rate of niobium is 91.01%, the loss rate of rare earths is 5.21%, and the purity of niobium oxide in this example is 99.01%. See Table 1 for details.

[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 is not added. The leaching rate of niobium, the loss rate of rare earths, and the purity of the final product niobium oxide obtained 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 addition amount of the activator NaCl, as shown in Table 1 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 addition amount of the activator NaCl, as shown in Table 1 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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-to-ore ratio of roasting, as shown in Table 1 specifically. The leaching rate of niobium, the loss rate of rare earths, and the purity of the finally obtained niobium oxide product 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 lies in the liquid-solid ratio during leaching, as shown in Table 1. The niobium leaching rate, the loss rate of rare earths, and the purity of the final product niobium oxide are shown in Table 1.

[0088] Table 1

[0089]

[0090]

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

[0092] Comparing Example 1 with Comparative Example 1, it can be seen that when the activator NaCl particles are not added, the niobium leaching rate of the niobium concentrate is relatively low, the amount of rare earths dissolved in the leaching solution is large, and the loss rate of rare earths in the slag is relatively large. This is mainly because the niobium minerals in the niobium concentrate are not completely reacted. In addition, since there is no sodium in the rare earth sulfate formed in the leaching solution, no double salt precipitate is formed, and a large amount of rare earths enter the leaching solution during leaching. The rare earths cannot be completely removed during the impurity removal process of the niobium-containing leaching solution, and TBP can extract rare earths, resulting in a decrease in the purity of the subsequent niobium oxide product.

[0093] Comparing Example 1 with Comparative Example 2, it can be seen that when the amount of activator added is small, the niobium minerals in the concentrate are not completely reacted during roasting, the niobium recovery rate (i.e., the niobium leaching rate) is lower than 90%, and the insufficient sodium content leads to the loss of rare earths. There are a large amount of rare earths in the leaching solution, resulting in problems in subsequent impurity removal and extraction, and the purity of the niobium oxide product cannot reach more than 99%.

[0094] Comparing Example 1 with Comparative Example 3, it can be seen that when the amount of activator added is too large, it is instead not conducive to the leaching of niobium.

[0095] Comparing Example 1 with Comparative Example 4, it can be seen that when the roasting temperature is relatively low, the decomposition of niobium, rare earth and other minerals is not complete, so the niobium leaching rate is relatively low.

[0096] Comparing Example 1 with Comparative Example 5, it can be seen that when the roasting temperature is relatively high, it is easy to burn the formed niobium to death, reducing its activity and making it difficult to be leached.

[0097] Comparing Example 1 with Comparative Example 6, it can be seen that when the roasting time is relatively short, the niobium minerals are not completely decomposed, so the niobium leaching rate is relatively low.

[0098] Comparing Example 1 with Comparative Example 7, it can be seen that when the concentration of roasting sulfuric acid is relatively low, the decomposition of niobium minerals by sulfuric acid is not complete, so the niobium leaching rate is relatively low.

[0099] Comparing Example 1 with Comparative Example 8, it can be seen that when the acid-to-ore ratio during roasting is relatively low, the contact between sulfuric acid and minerals is not sufficient, and the decomposition of niobium minerals is not complete, so the niobium leaching rate is relatively low.

[0100] From the comparison between Example 1 and Comparative Example 9, it can be seen that when the liquid-solid ratio of leaching is low, the roasted ore does not contact water sufficiently, the leaching kinetic conditions are poor, and it is not conducive to the leaching and dissolution of niobium.

[0101] Therefore, according to the above comparison, it can be known that there is an optimal range for each parameter in the process. Exceeding this range will correspondingly reduce the element recovery rate and product purity.

[0102] Comparative Example 10

[0103] 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. The activator in this comparative example is potassium chloride.

[0104] In this comparative example, the leaching rate of niobium is 75.05%, the loss rate of rare earth is 6.09%, and the purity of niobium oxide is 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. The activator in this comparative example is ammonium chloride.

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

[0108] Comparative Example 12

[0109] 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. The activator in this comparative example is hydrochloric acid.

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

[0111] Comparative Example 13

[0112] 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. The activator in this comparative example is Ca2SO4.

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

[0114] From Example 1 and Comparative Examples 10 - 13, it can be seen that the type of activator will affect the leaching rate of niobium, the loss rate of rare earth, and the purity of niobium oxide.

[0115] Comparative Example 14

[0116] 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 as follows:

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

[0118] B. Low-temperature roasting: Put the evenly mixed materials into a rotary kiln, heat to 340 °C, and keep warm for 2 hours to fully react the niobium minerals with the rare earth minerals;

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

[0120] D. Water leaching: For the materials after low-temperature roasting, leach in a leaching tank at a liquid-solid ratio of 8:1 for 2 h, with a stirring rate of 200 r / min to leach the niobium minerals.

[0121] In this comparative example, the leaching rate of niobium is 5.04%, and the loss rate of rare earth is 4.12%. This is mainly because in this comparative example, the niobium minerals are hardly decomposed during roasting without concentrated sulfuric acid, resulting in the inability of concentrated sulfuric acid to decompose the niobium minerals at room temperature.

[0122] Example 2

[0123] The chemical composition of the low-grade high-silicon niobium concentrate (abbreviated as niobium concentrate) used in this example is the same as that in Example 1, and the smelting method is as follows:

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

[0125] B. Low-temperature roasting: Put the evenly mixed furnace charge into a rotary kiln, heat to 380 °C, and keep warm for 2 hours to fully react the niobium minerals with the rare earth minerals;

[0126] C. Water leaching: Immediately add the materials after low-temperature roasting to a water-containing leaching tank at a liquid-solid ratio of 6:1, leach for 2 h, with a stirring rate of 200 r / min to leach the niobium minerals;

[0127] D. After the leaching is completed, filter to obtain a leaching solution and a filter residue, wash the filter residue, the leaching solution is a niobium-containing leaching solution, and the filter residue is a filter residue containing silicon minerals and rare earth double salts;

[0128] E. Same as Example 1.

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

[0130] Example 3

[0131] The chemical composition (mass percentage) of the low-grade high-silicon type niobium concentrate (referred to as niobium concentrate) used in this example is: 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%, others: 7.73%.

[0132] The smelting method is as follows:

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

[0134] B. Low-temperature roasting: Place the evenly mixed furnace charge into a rotary kiln, heat to 400 °C, and keep it warm for 2 hours to fully react the niobium minerals with the rare earth minerals.

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

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

[0137] E. Same as Example 1.

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

[0139] Example 4

[0140] The chemical composition (mass percentage) of the low-grade high-silicon niobium concentrate (referred to as niobium concentrate) used in this example is: 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%, others: 20.02%;

[0141] The smelting method is as follows:

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

[0143] B. Low-temperature roasting: Place the evenly mixed furnace charge into a rotary kiln, heat it to 250 °C, and keep it warm for 3 hours to make the niobium minerals and rare earth minerals fully react;

[0144] C. Water leaching: Immediately add the material after low-temperature roasting to a water-containing leaching tank according to a liquid-solid ratio of 5:1, leach for 2 h, and the stirring rate is 200 r / min to leach the niobium minerals;

[0145] D. After the leaching is completed, filter to obtain the leaching solution and filter residue, wash the filter residue, the leaching solution is the niobium-containing leaching solution, and the filter residue is the filter residue containing silicon minerals and rare earth double salts;

[0146] E. The same as Example 1.

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

[0148] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

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

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

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

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

5. The sulfuric acid smelting method of low-grade high-silicon niobium concentrate according to claim 2, characterized in that: The calcination temperature is 250-400° C., and the heat preservation time is 1-3 hours.

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

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

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

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