Method for synergistically decomposing low-grade niobium ore and fluorine-containing ore

Abstract

The invention discloses a method for synergistically decomposing low-grade niobium ore and fluorine-containing ore, which comprises the following steps: 1) mixing the low-grade niobium ore, the fluorine-containing ore and a sulfuric acid aqueous solution to obtain mixed slurry I; roasting the mixed slurry I to obtain roasted ore and roasted gas; 2) crushing and grinding the roasted ore to obtain roasted ore powder; mixing the roasted mineral powder with water to obtain mixed slurry II; leaching the mixed slurry II to obtain a leached product; and carrying out solid-liquid separation on the leaching product to obtain a leaching solution and leaching residues. According to the method, the low-grade niobium ore and the fluorine-containing ore are decomposed and leached together, and the leaching rate can be increased without adding a fluoride reagent and roasting at high temperature.

Description

Technical Field

[0001] The invention relates to a method for collaborative decomposition of low-grade niobium ore and fluorine-containing ore. Background Art

[0002] Niobium (Nb) is a refractory metal with a melting point of 2467°C. It exhibits excellent heat resistance, high plasticity, high thermal conductivity, high structural strength, high corrosion resistance, and good weldability. Alloys of niobium with other metals exhibit excellent high-temperature strength and low-temperature plasticity, and are widely used as structural materials in supersonic jet aircraft, rockets, and missiles, as well as in electronics, precision ceramics, biomedicine, superconductivity, atomic energy, and steel.

[0003] Currently, the Bayan Obo rare earth mine uses a "weak magnetic-strong magnetic-flotation" process to separate iron, rare earths, and fluorite, resulting in fluorite tailings. This is then processed through iron separation and desulfurization to produce low-grade niobium ore. This low-grade niobium ore contains approximately 0.1-15% niobium by weight, 1-3% rare earths by weight, and 20-50% iron by weight.

[0004] Niobium ore decomposition processes primarily include chlorination, alkaline decomposition, and acid decomposition. The chlorination method utilizes the differences in the chlorination thermodynamic properties of various components in the niobium concentrate to control the chlorination reaction conditions and convert the desired component into gaseous or condensed chlorides, thereby separating it from other components. The chlorinating agent used in this process is highly corrosive, easily corroding equipment and placing high demands on environmental protection.

[0005] Alkali decomposition methods primarily include alkali fusion and alkaline hydrothermal methods. The alkali fusion method, however, suffers from high alkali consumption, high reaction temperatures (500-800°C), and short crucible life, leading to its gradual elimination. The alkaline hydrothermal method typically uses a 35-45% caustic solution of NaOH and KOH at 150-250°C and an oxygen pressure of 0.4-0.5 MPa to decompose niobium-containing minerals, breaking them down into hexaniobate, which is then converted into insoluble metaniobate. This method requires pressure operation, making process control more challenging and difficult to commercialize.

[0006] Acid decomposition methods primarily include hydrofluoric acid decomposition and sulfuric acid decomposition. Hydrofluoric acid decomposition is the most widely used hydrometallurgical niobium extraction process. Due to the highly corrosive nature of hydrofluoric acid, it requires high equipment requirements, and the HF-containing flue gas produced during the reaction poses a serious environmental risk. Due to the low niobium content and the wide variety of impurity elements in the niobium-containing tailings obtained from the Bayan Obo rare earth ore treatment, direct hydrofluoric acid decomposition is not suitable.

[0007] The sulfuric acid decomposition method is divided into direct leaching with sulfuric acid solution (approximately 100-200°C) and sulfuric acid roasting-leaching (approximately 200-330°C). In a concentrated sulfuric acid medium, most elements in the niobium concentrate are decomposed into soluble sulfates and enter the solution. The resulting alkaline earth metal sulfates are diluted and can be hydrolyzed step by step to separate the hydroxides of different metals by adjusting the pH value of the solution.

[0008] CN1904097A discloses a method for producing industrial-grade and high-purity fluorine-free niobium oxide using an oxalic acid extraction process. The method comprises: crushing and ball-milling the niobium-containing raw material, followed by sulfuric acid roasting to decompose the mineral; washing the roasted clinker with water to hydrolyze the niobium oxysulfate generated during roasting to produce niobium hydroxide and remove some impurities such as iron and manganese; leaching the filter cake with oxalic acid to produce a water-soluble niobium oxalate complex; extracting the niobium and separating impurities using solvent extraction; vacuum concentration and stripping to obtain niobium oxalate crystals; and calcining the niobium oxalate crystals to produce niobium oxide. This method is suitable for raw materials with a niobium oxide content greater than 30% by weight. Magnetic separation is required for raw materials with a high iron content. Raw materials with a niobium oxide content less than 10% by weight require acid treatment to achieve a niobium oxide grade of 25% or higher. Since the niobium content in niobium-containing rare earth tailings is as low as 0.1-15wt%, the acid treatment process cannot increase its grade to above 25wt%, so this method is not suitable for low-grade niobium-containing rare earth tailings.

[0009] CN105568003A discloses a method for enriching niobium from Bayan Obo tailings. The method comprises the following steps: (1) leaching the tailings obtained from the selection of iron and rare earth elements from the Bayan Obo ore or the niobium concentrate obtained from the selection of niobium from the Bayan Obo ore with an inorganic acid; (2) roasting the resulting acid leaching residue at 500-900°C to obtain a roasted ore; (3) leaching the roasted ore with a sodium hydroxide solution at 80-100°C, filtering, and washing to obtain a solid niobium concentrate. This method requires high-temperature roasting of the acid leaching residue and alkali leaching of the roasted ore, resulting in high energy consumption and processing costs. Furthermore, the niobium element in this method is enriched in the alkaline leaching residue, requiring further dissolution and separation.

[0010] CN115893490A discloses a method for the comprehensive extraction of niobium, titanium, and rare earth elements from pyrochlore ore. This method uses pyrochlore ore as the raw material and first obtains a niobium concentrate through a combined magnetic separation and gravity separation process. The niobium concentrate is then subjected to sulfuric acid thermal decomposition, leaching, flotation extraction, and stripping to produce a rare earth-rich solution and niobium-titanium hydrate. The niobium-titanium hydrate is then acid-washed, acid-dissolved, hydrolyzed, and calcined to produce niobium pentoxide and titanium dioxide. This method is applicable to niobium ores in which more than 90% by weight of niobium exists in the pyrochlore phase. The niobium-containing rare earth tailings in Bayan Obo are primarily composed of calcite, pyrochlore, niobium iron ore, and niobium iron rutile. The mineral composition is complex, and the decomposition of niobium iron rutile and niobium iron ore requires higher temperatures and acidity. Therefore, this method is not applicable to the niobium-containing rare earth tailings in Bayan Obo.

[0011] CN118957310A discloses a method for extracting niobium from low-grade niobium-containing ore. The method comprises: (1) mixing the low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, roasting, and primary leaching of niobium; (2) mixing the mixture after primary leaching with a fluoride salt and water, and secondary leaching of niobium; (3) separating the solid and liquid of the mixture after secondary leaching, and extracting niobium from the resulting filtrate. This method requires the addition of ammonium sulfate and fluoride salts, which is relatively costly.

[0012] CN118979161A discloses a method for the combined extraction of ferroniobium from the Bayan Obo rare earth tailings. The method comprises: (1) acid-washing the Bayan Obo rare earth tailings, filtering, and obtaining an acid wash solution and a filter residue; (2) drying the filter residue, mixing it with ammonium sulfate and concentrated sulfuric acid, and roasting it to extract niobium for the first time; mixing the mixture after the first leaching with a fluoride salt and water, extracting niobium for the second time, separating the solid and the liquid, and extracting niobium from the resulting filtrate to obtain a raffinate and an extract containing niobium ions; (3) mixing the acid wash solution and the raffinate, adjusting the pH to 3-4.5, and then adding a hydrogen peroxide solution to carry out a precipitation reaction to form an Fe(OH)3 precipitate. This method also requires acid washing before the rare earth tailings are roasted and leached with sulfuric acid, and requires the addition of ammonium sulfate and a fluoride salt, which is costly. Summary of the Invention

[0013] In view of this, the object of the present invention is to provide a method for the synergistic decomposition of low-grade niobium ore and fluorine-containing ore. This method decomposes and leaches low-grade niobium ore and fluorine-containing ore together to achieve the synergistic extraction of niobium and fluorine, iron, and rare earth elements, and can improve the leaching rate without adding fluoride reagents and high-temperature roasting.

[0014] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0015] The method for collaborative decomposition of low-grade niobium ore and fluorine-containing ore provided by the present invention comprises the following steps:

[0016] 1) mixing low-grade niobium ore, fluorine-containing ore and sulfuric acid aqueous solution in a weight ratio of 1:0.1 to 3:2 to 5 to obtain a mixed slurry I; roasting the mixed slurry I at 120 to 350° C. to obtain a roasted ore and a roasting gas; wherein the mass concentration of the sulfuric acid aqueous solution is 50 to 98 wt%;

[0017] 2) crushing and grinding the roasted ore to obtain roasted ore powder; mixing the roasted ore powder with water in a weight ratio of 0.5 to 15:1 to obtain a mixed slurry II; leaching the mixed slurry II at 20 to 60° C. to obtain a leached product; and separating the leached product into a solid and liquid to obtain a leachate and a leached residue.

[0018] According to the method of the present invention, preferably, in step 1), the weight ratio of the low-grade niobium ore, the fluorine-containing ore and the sulfuric acid aqueous solution is 1:0.2-2.5:2.5-4.5.

[0019] According to the method of the present invention, preferably, in step 1), the calcination temperature is 125-320°C.

[0020] According to the method of the present invention, preferably, in step 1), the calcination time is 1 to 8 hours.

[0021] According to the method of the present invention, preferably, in step 2), the particle size of the roasted ore powder is -100 to -300 mesh.

[0022] According to the method of the present invention, preferably, in step 2), the weight ratio of the roasted ore powder to water is 1 to 12:1.

[0023] According to the method of the present invention, preferably, in step 2), the leaching temperature is 22-55°C.

[0024] According to the method of the present invention, preferably, in step 2), the leaching time is 0.5 to 5 hours.

[0025] According to the method of the present invention, preferably, in step 2), stirring is performed during the leaching process, and the stirring speed is 200-400 rpm.

[0026] According to the method of the present invention, preferably, the roasting gas is subjected to condensation recovery and purification treatment in steps to obtain hydrofluoric acid, fluosilicic acid and sulfuric acid.

[0027] This method decomposes and leaches low-grade niobium ore and fluorine-containing ore together, achieving synergistic extraction of niobium, fluorine, iron, and rare earth elements. This method improves leaching efficiency without the need for adding fluoride reagents or high-temperature roasting. This method reduces energy consumption and costs, improving the comprehensive resource utilization of low-grade niobium ore. Compared to hydrofluoric acid decomposition processes, this method is more adaptable to a wider range of raw material grades, has lower equipment requirements, reduces fluorine-containing flue gas pollution, and enables the synergistic extraction of multiple mineral species. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a process flow chart. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] The "REO" mentioned in the present invention refers to rare earth oxides.

[0031] <Method for synergistic decomposition of low-grade niobium ore and fluorine-containing ore>

[0032] The method for the synergistic decomposition of low-grade niobium ore and fluorine-containing ore of the present invention comprises a mixing and decomposition step and a water leaching step. Preferably, it also includes a roasting gas recovery step. This is described in detail below.

[0033] Mixing and disintegration steps

[0034] Low-grade niobium ore, fluorine-containing ore and sulfuric acid aqueous solution are mixed in a weight ratio of 1:0.1-3:2-5 to obtain a mixed slurry I; the mixed slurry I is roasted at 120-350° C. to obtain a roasted ore and a roasting gas.

[0035] The present invention is applicable to low-grade niobium-containing tailings obtained after iron separation and rare earth extraction of all types of rare earth ores, preferably low-grade niobium ore obtained by further iron separation and desulfurization of fluorite tailings obtained by separation of iron, rare earth elements and fluorite from Bayan Obo rare earth ore, more preferably low-grade niobium ore having the following main components by weight percentage:

[0036] Nb2O5 0.1~15wt%, TFe 4~55wt% and REO 1~20wt%.

[0037] The low-grade niobium ore of the present invention may have a Nb2O5 content of 0.1 to 15 wt%, preferably 0.15 to 14.5 wt%, and more preferably 0.2 to 13 wt%. The TFe content may be 4 to 55 wt%, preferably 5 to 52 wt%, and more preferably 6 to 50 wt%. The REO content may be 1 to 20 wt%, preferably 1.2 to 18 wt%, and more preferably 1.5 to 15 wt%.

[0038] According to a preferred embodiment of the present invention, the rare earth element oxides in REO are as follows by weight percentage: La2O3 10.5wt%, CeO2 43.9wt%, Pr6O 11 7.4wt%, Nd2O3 28.1wt%, and the remainder are oxides of medium and heavy rare earth elements.

[0039] In the present invention, the content of La2O3 can be 2.5 to 12 wt%, preferably 3 to 11.5 wt%, more preferably 3.5 to 11 wt%. The content of CeO2 can be 26 to 45 wt%, preferably 28 to 44.5 wt%, more preferably 29 to 44 wt%. Pr6O 11 The content of Nd2O3 can be 6-10 wt%, preferably 6.5-9 wt%, more preferably 7-8.5 wt%. The content of Nd2O3 can be 26-42 wt%, preferably 27-41 wt%, more preferably 28-40.5 wt%.

[0040] The fluorine-containing ore of the present invention can be any type of fluorine-containing ore known in the art, preferably at least one of fluorite concentrate, fluorocarbon cerium ore, fluorocarbon calcium cerium ore, fluorocarbon barium cerium ore, and fluorapatite ore produced in Bayan Obo, and more preferably at least one of fluorite concentrate and fluorocarbon cerium ore produced in Bayan Obo.

[0041] According to a preferred embodiment of the present invention, the CaF2 content of the fluorite concentrate can be 75-96wt% by weight, preferably 76-95wt%, and more preferably 77-94wt%.

[0042] According to a preferred embodiment of the present invention, the REO content of the bastnaesite may be 60-70 wt %, preferably 62-68.5 wt %, and more preferably 65-68 wt %. The fluorine content may be 6-9.8 wt %, preferably 6.5-9.5 wt %, and more preferably 7-8.5 wt %.

[0043] According to one embodiment of the present invention, the mass concentration of the aqueous sulfuric acid solution may be 50 to 98 wt %, preferably 60 to 98 wt %, and more preferably 70 to 98 wt %.

[0044] According to one embodiment of the present invention, the weight ratio of low-grade niobium ore, fluorine-containing ore and sulfuric acid aqueous solution can be 1:0.1-3:2-5, preferably 1:0.2-2.5:2.5-4.5, and more preferably 1:0.3-2:2.6-4.

[0045] Reasonable reactant ratio and sulfuric acid concentration are conducive to the enrichment of niobium, iron and rare earth elements in the solid roasted ore, and the fluorine element forms roasting gas and is effectively separated and recovered.

[0046] According to one embodiment of the present invention, the calcination temperature may be 120-350° C., preferably 125-320° C., more preferably 130-300° C. The calcination time may be 1-8 hours, preferably 1.5-6 hours, more preferably 2-5 hours.

[0047] Reasonable roasting conditions are conducive to the enrichment of niobium, iron and rare earth elements in the solid roasted ore, and the fluorine element forms roasting gas and is effectively separated and recovered.

[0048] The roasting of the present invention can be carried out using any type of roasting equipment known in the art, which will not be described in detail here, for example, a tubular furnace or a rotary kiln.

[0049] Water leaching step

[0050] The roasted ore is crushed and ground to obtain roasted ore powder; the roasted ore powder is mixed with water in a weight ratio of 0.5 to 15:1 to obtain a mixed slurry II; the mixed slurry II is leached at 20 to 60° C. to obtain a leaching product; the leaching product is solid-liquid separated to obtain a leachate and a leaching residue.

[0051] According to one embodiment of the present invention, the particle size of the roasted ore powder can be -100 to -300 mesh, preferably -120 to -280 mesh, and more preferably -150 to -250 mesh. In the present invention, the proportion of the roasted ore powder having a particle size within the above range can be 94 to 100%, preferably 94.5 to 99.5%, and more preferably 95 to 99%.

[0052] According to one embodiment of the present invention, the crushing may be primary crushing or secondary crushing.

[0053] In the present invention, the primary crushing may include: crushing the roasted ore into coarse powder, and grinding the coarse powder to obtain roasted ore powder.

[0054] According to a preferred embodiment of the present invention, in the primary crushing, the particle size of the coarse crushed powder may be 1 to 3 mm, preferably 1.2 to 2.6 mm, and more preferably 1.5 to 2.5 mm.

[0055] The primary crushing can be achieved using any type of crushing equipment known in the art, without particular limitation herein, such as a jaw crusher, a rod mill, and the like.

[0056] In the present invention, the secondary crushing may include: crushing the roasted ore into coarse powder, then crushing the coarse powder into medium powder, and grinding the medium powder to obtain roasted ore powder.

[0057] According to a preferred embodiment of the present invention, in the secondary crushing, the particle size of the coarse crushing can be 10-20 mm, preferably 12.5-18.5 mm, more preferably 12-18 mm. The particle size of the medium crushing can be 1-5 mm, preferably 1.5-4.5 mm, more preferably 2-4 mm.

[0058] In the secondary crushing process, the coarse powder can be produced using any type of crushing equipment known in the art, without particular limitation. For example, a jaw crusher can be used. The secondary powder can be produced using any type of crushing equipment known in the art, without particular limitation. For example, a double-roll crusher can be used.

[0059] According to one embodiment of the present invention, the grinding can be achieved using any type of grinding equipment known in the art, without particular limitation herein, such as a rod mill, a three-head grinder, and the like.

[0060] According to one embodiment of the present invention, the weight ratio of roasted ore powder to water may be 0.5 to 15:1, preferably 1 to 12:1, and more preferably 2 to 10:1.

[0061] Limiting the weight ratio of roasted ore powder to water within the above range is beneficial to improving the leaching rate of niobium, iron and rare earth elements and achieving effective recovery and reuse of niobium, iron and rare earth elements.

[0062] According to one embodiment of the present invention, the leaching temperature may be 20-60° C., preferably 22-55° C., more preferably 25-50° C. The leaching time may be 0.5-5 h, preferably 1-4.5 h, more preferably 1.5-4 h.

[0063] According to a preferred embodiment of the present invention, stirring may be performed during the leaching process, and the stirring speed may be 200-400 rpm, preferably 220-380 rpm, and more preferably 250-350 rpm.

[0064] In the present invention, stirring can use any type of high temperature resistant stirring equipment known in the art, which will not be described in detail here.

[0065] According to one embodiment of the present invention, the reaction time may be 0.5 to 5 hours, preferably 0.8 to 4 hours, and more preferably 1 to 3 hours.

[0066] In the present invention, the stirring rotation speed may be 200 to 400 rpm, preferably 220 to 380 rpm, and more preferably 250 to 350 rpm.

[0067] Reasonable leaching conditions are conducive to improving the leaching rates of niobium, iron and rare earth elements, and realizing the effective recycling and reuse of niobium, iron and rare earth elements.

[0068] The water involved in the present invention can be any type of water known in the art that can be used for leaching and separation of rare earth elements, and will not be described in detail here.

[0069] The solid-liquid separation involved in the present invention can be achieved using any filtration method or filtration equipment known in the art, which will not be described in detail herein. For example, a Buchner funnel vacuum filtration system, a horizontal centrifuge, a vacuum filter, etc. can be used.

[0070] According to one embodiment of the present invention, the leaching rate of niobium in the leachate can be 85-97 wt%, preferably 86.5-96 wt%, and more preferably 88-95 wt%. The leaching rate of rare earth elements (REO) can be 73-97 wt%, preferably 74-96.5 wt%, and more preferably 76-99 wt%. The leaching rate of iron can be 77-98.5 wt%, preferably 79-98 wt%, and more preferably 79-98 wt%.

[0071] Roasting gas recovery steps

[0072] The roasting gas is condensed, recovered and purified in steps to obtain hydrofluoric acid, fluosilicic acid and sulfuric acid.

[0073] According to one embodiment of the present invention, the roasting gas is subjected to condensation recovery and purification step by step, which may include the following steps:

[0074] S1) spraying the roasting flue gas to cool it to 70-160° C. to obtain washed flue gas; wherein the spraying washing liquid is a sulfuric acid aqueous solution;

[0075] S2) sequentially subjecting the scrubbed flue gas to a primary condensation treatment at a temperature of -16 to -10°C and a secondary condensation treatment at a temperature of -32 to -20°C to obtain condensed HF and uncondensed gas;

[0076] S3) treating the uncondensed gas by sulfuric acid absorption and tertiary water absorption to obtain a fluosilicic acid solution.

[0077] According to a preferred embodiment of the present invention, in step S1), the temperature can be lowered by spraying to 70-160° C., preferably 75-155° C., and more preferably 80-150° C. The mass concentration of the aqueous sulfuric acid solution used as the washing liquid can be 90-98 wt %, preferably 92.5-98 wt %, and more preferably 93-98 wt %.

[0078] In the present invention, after spray cooling, 90-95 wt% of dust and sulfuric acid mist can be removed from the roasting flue gas, thereby achieving the separation and recovery of part of the sulfuric acid. The washing liquid can be recycled until the mass concentration of sulfuric acid reaches 60-80 wt%, preferably 62-78 wt%, and more preferably 65-75 wt%, and then returned to the mixed acid tank for acid preparation.

[0079] In the present invention, the spray cooling can be implemented in any spray device for acid gas purification known in the art, and is not particularly limited here. For example, it can be a scrubber.

[0080] According to a preferred embodiment of the present invention, in step S2), the temperature of the primary condenser may be -16 to -10°C, preferably -16 to -12°C, and more preferably -15 to -12°C. The temperature of the secondary condenser may be -32 to -20°C, preferably -32 to -23°C, and more preferably -30 to -23°C.

[0081] In the present invention, the primary condensation process and the secondary condensation process can be carried out in any condensation device known in the art for hydrogen fluoride purification, without particular limitation herein, such as a PFA (perfluoroalkoxy resin) condenser, a PTFE (polytetrafluoroethylene) condenser, or the like.

[0082] In the present invention, after the primary condensation treatment and the secondary condensation treatment, the total recovery rate of HF can be 99-99.5%, preferably 99.2-99.5%, and more preferably 99.2-99.3%. In the present invention, the condensed HF can also be purified in a rectification column to obtain anhydrous hydrofluoric acid. The purity of the purified anhydrous hydrofluoric acid can be 99.9-99.96 wt%, preferably 99.93-99.96 wt%, and more preferably 99.93-99.95 wt%.

[0083] According to a preferred embodiment of the present invention, in step S3), the mass concentration of the hydrosilicofluoric acid solution may be 28-35 wt%, preferably 29-34 wt%, and more preferably 30-33 wt%.

[0084] In the present invention, sulfuric acid absorption and tertiary water absorption can be performed in any tertiary water absorption apparatus known in the art for acidic gas, without particular limitation. For example, a sulfuric acid absorption tower or a tertiary water absorption tower can be used. After the uncondensed gas undergoes sulfuric acid absorption and tertiary water absorption, a fluosilicic acid solution is produced, while a portion of sulfuric acid is separated and recovered.

[0085] <Test method>

[0086] Determination of Nb content: Inductively coupled plasma optical emission spectrometry was used.

[0087] Determination of Fe content: Inductively coupled plasma optical emission spectrometry was used.

[0088] Determination of REO content: Inductively coupled plasma optical emission spectrometry was used.

[0089] Determination of F content: fluoride ion selective electrode method was used.

[0090] <Ingredients>

[0091] Unless otherwise specified, the raw materials in the following examples are all commercially available products.

[0092] Example 1

[0093] The low-grade niobium ore and fluorine-containing ore used in this example are all from Bayan Obo.

[0094] The main components of low-grade niobium ore are as follows by weight percentage: Nb2O5 2wt%, TFe48.2wt% and REO2.5wt%; among them, the rare earth element oxides in REO are as follows by weight percentage: La2O3 10.5wt%, CeO243.9wt%, Pr6O 11 7.4wt%, Nd2O3 28.1wt%, and the remainder are oxides of medium and heavy rare earth elements.

[0095] The fluorine-containing ore is fluorite concentrate, and the CaF2 content of the fluorite concentrate is 93.7wt%.

[0096] The synergistic decomposition of low-grade niobium ore and fluorite concentrate is carried out in the following steps:

[0097] 1) Mixing and Acid Decomposition: Low-grade niobium ore, fluorite concentrate, and a 98 wt% aqueous sulfuric acid solution were uniformly mixed in a weight ratio of 1:1:3.2 to obtain a mixed slurry I. The mixed slurry I was placed in a rotary kiln and roasted at 220° C. for 4 hours to obtain a roasted ore and roasting flue gas.

[0098] 2) Water Leaching: The roasted ore was crushed to a particle size of 15 mm using a jaw crusher to obtain a coarse powder. The coarse powder was crushed to a particle size of 3 mm using a double-roll crusher to obtain a medium powder. The medium powder was ground using a universal rod mill for 5 minutes to obtain a roasted ore powder with a particle size of -200 mesh, accounting for 95%. The roasted ore powder was mixed with water in a weight ratio of 10:1 to obtain a mixed slurry II. The mixed slurry II was leached for 2 hours at 25°C and a stirring speed of 260 rpm to obtain a leached product. The leached product was filtered through a Buchner funnel vacuum filtration system (equipped with a microporous filter membrane with a pore size of 0.45 μm and maintained at a pressure of -0.085 MPa) to obtain a leachate and a leached residue. The leaching rates of niobium, rare earth elements (REO), and iron in the leachate were 93.5 wt%, 78 wt%, and 91.5 wt%, respectively.

[0099] 3) Roasting Gas Recovery: The roasting flue gas is sprayed in a scrubbing tower with a 93% aqueous sulfuric acid solution as a scrubbing liquid, cooled to 150°C, and 90% of the dust and sulfuric acid mist are removed to obtain the scrubbed flue gas. The scrubbing liquid is recycled until the sulfuric acid concentration reaches 70% by weight, and then returned to the mixed acid tank for acid preparation. The scrubbed flue gas is sequentially passed through a primary condenser at a temperature of -12°C and a secondary condenser at a temperature of -23°C to obtain condensed HF and uncondensed gas, with a total HF recovery rate of 99.2%. The condensed HF is purified in a distillation tower to obtain anhydrous hydrofluoric acid with a purity of 99.93% by weight. The uncondensed gas is sequentially treated in a sulfuric acid absorption tower and a tertiary water absorption tower to produce a 30% by weight fluosilicic acid solution.

[0100] Example 2

[0101] The low-grade niobium ore and fluorine-containing ore used in this example are all from Bayan Obo.

[0102] The main components of low-grade niobium ore are as follows by weight percentage: Nb2O5 12.8wt%, TFe 6.3wt% and REO 14.3wt%; among them, the rare earth element oxides in REO are as follows by weight percentage: La2O3 5.4wt%, CeO232.5wt%, Pr6O 11 7.6wt%, Nd2O331.5wt%, and the remainder are oxides of medium and heavy rare earth elements.

[0103] The fluorine-containing ore is fluorite concentrate, and the CaF2 content of the fluorite concentrate is 77.9wt%.

[0104] The synergistic decomposition of low-grade niobium ore and fluorite concentrate is carried out in the following steps:

[0105] 1) Mixing and Acid Decomposition: Low-grade niobium ore, fluorite concentrate, and a 95 wt% aqueous sulfuric acid solution were uniformly mixed in a weight ratio of 1:2:4 to obtain a mixed slurry I. The mixed slurry I was placed in a tube furnace and roasted at 300° C. for 4 hours to obtain a roasted ore and roasting flue gas.

[0106] 2) Water leaching: The ore was crushed to a particle size of 2 mm using a jaw crusher to obtain a coarse powder. The coarse powder was ground using a three-head grinder for 5 minutes to obtain a roasted ore powder with a particle size of -200 mesh accounting for 98%. The roasted ore powder was mixed with water in a weight ratio of 10:1 to obtain a mixed slurry II. The mixed slurry II was leached for 4 hours under stirring conditions of 30°C and a rotation speed of 300 rpm to obtain a leached product. The leached product was placed in a horizontal centrifuge and centrifuged at a rotation speed of 1500 rpm for 15 minutes to obtain a leachate and a leaching residue. The leaching rates of niobium, rare earth elements (REO) and iron in the leachate were 90wt%, 75.2wt% and 85.2wt%, respectively.

[0107] 3) Roasting Gas Recovery: The roasting flue gas is sprayed in a scrubbing tower using a 95wt% aqueous sulfuric acid solution as a scrubbing liquid, cooled to 150°C, and 90wt% of the dust and sulfuric acid mist is removed to produce the scrubbed flue gas. The scrubbing liquid is recycled until the sulfuric acid concentration reaches 70wt% and then returned to the mixed acid tank for acid preparation. The scrubbed flue gas is sequentially passed through a primary condenser at -15°C and a secondary condenser at -25°C to produce condensed HF and uncondensed gas, with a total recovery rate of condensed HF of 99.2%. The condensed HF is purified in a distillation tower to obtain anhydrous hydrofluoric acid with a purity of 99.93wt%. The uncondensed gas is sequentially treated in a sulfuric acid absorption tower and a tertiary water absorption tower to produce a 32wt% fluosilicic acid solution.

[0108] Example 3

[0109] The low-grade niobium ore and fluorine-containing ore used in this example are all from Bayan Obo.

[0110] The main components of low-grade niobium ore are as follows by weight percentage: Nb2O5 0.23wt%, TFe 26.1wt%, REO 1.51wt%; among them, the rare earth element oxides in REO are as follows by weight percentage: La2O3 3.9wt%, CeO2 29.5wt%, Pr6O 11 8.1wt%, Nd2O340wt%, and the balance are oxides of medium and heavy rare earth elements.

[0111] The fluorine-containing ore is fluorite concentrate, and the CaF2 content of the fluorite concentrate is 83.3wt%.

[0112] The specific steps for synergistic decomposition of low-grade niobium ore and fluorite ore are as follows:

[0113] 1) Mixing and Acid Decomposition: Low-grade niobium ore, fluorite concentrate, and a 70 wt% aqueous sulfuric acid solution were uniformly mixed in a weight ratio of 1:0.3:2.6 to obtain a mixed slurry I. The mixed slurry I was placed in a tubular reactor and roasted at 140° C. for 2 hours to obtain a roasted ore and roasting flue gas.

[0114] 2) Water leaching: The roasted ore is crushed to a particle size of 2 mm by a jaw crusher to obtain coarse powder. The coarse powder is ground by a three-head grinder for 5 minutes to obtain a roasted ore powder with a particle size of -200 mesh accounting for 98.5%. The roasted ore powder is mixed with water in a weight ratio of 5:1 to obtain a mixed slurry II. The mixed slurry II is leached for 4 hours under stirring conditions of 50°C and a rotation speed of 300rpm to obtain a leaching product. The leaching product is filtered through a vacuum filter to obtain a leachate and a leaching residue. The leaching rates of niobium, rare earth elements (REO) and iron in the leachate are 88.9wt%, 79.4wt% and 79.3wt%, respectively.

[0115] 3) Roasting Gas Recovery: The roasting flue gas is sprayed in a scrubbing tower using a 95wt% aqueous sulfuric acid solution as a scrubbing liquid, cooled to 80°C, and 95wt% of the dust and sulfuric acid mist is removed to produce the scrubbed flue gas. The scrubbing liquid is recycled until the sulfuric acid concentration reaches 70wt% and then returned to the mixed acid tank for acid preparation. The scrubbed flue gas is sequentially passed through a primary condenser at -15°C and a secondary condenser at -30°C to produce condensed HF and uncondensed gas, with a total HF recovery rate of 99.3%. The condensed HF is purified in a distillation tower to obtain anhydrous hydrofluoric acid with a purity of 99.93wt%. The uncondensed gas is sequentially treated in a sulfuric acid absorption tower and a tertiary water absorption tower to produce a 31.3wt% fluosilicic acid solution.

[0116] Example 4

[0117] The low-grade niobium ore and fluorine-containing ore used in this example are all from Bayan Obo.

[0118] The main components of low-grade niobium ore are as follows by weight percentage: Nb2O5 0.23wt%, TFe 26.1wt% and REO 1.51wt%; among them, the rare earth element oxides in REO are as follows by weight percentage: La2O3 3.9wt%, CeO2 29.5wt%, Pr6O 11 8.1wt%, Nd2O340wt%, and the balance are oxides of medium and heavy rare earth elements.

[0119] The fluorine-containing ore is bastnaesite, and the REO content of the bastnaesite is 67 wt % and the F content is 7.57 wt %.

[0120] The synergistic decomposition of low-grade niobium ore and bastnaesite is carried out in the following steps:

[0121] 1) Mixing and Acid Decomposition: Low-grade niobium ore, bastnaesite, and a 98 wt% aqueous sulfuric acid solution were uniformly mixed in a weight ratio of 1:1:3.2 to obtain a mixed slurry I. The mixed slurry I was placed in a tube furnace and roasted at 300° C. for 4 hours to obtain a roasted ore and roasting flue gas.

[0122] 2) Water leaching: The roasted ore is crushed to a particle size of 2 mm by a rod mill to obtain coarse powder. The coarse powder is ground through a three-head grinder for 5 minutes to obtain a roasted ore powder with a particle size of -200 mesh accounting for 98%. The roasted ore powder is mixed with water in a weight ratio of 8:1 to obtain a mixed slurry II. The mixed slurry II is leached for 2 hours under stirring conditions of 25°C and a rotation speed of 260rpm to obtain a leaching product. The leached product is filtered through a vacuum filter to obtain a leachate and a leaching residue. The leaching rates of niobium, rare earth elements (REO) and iron in the leachate are 95wt%, 96wt% and 98wt%, respectively.

[0123] 3) Roasting Gas Recovery: The roasting flue gas is sprayed in a high-temperature scrubber using a 98% wt aqueous sulfuric acid solution as a scrubber, cooled to 80°C, and 92% of the dust and sulfuric acid mist is removed to produce the scrubbed flue gas. The scrubbing liquid is recycled until the sulfuric acid concentration reaches 70% wt, and then returned to the mixed acid tank for acid preparation. The scrubbed flue gas is sequentially passed through a primary condenser at -15°C and a secondary condenser at -25°C to produce condensed HF and uncondensed gas, with a total HF recovery rate of 99.2%. The condensed HF is purified in a distillation tower to obtain anhydrous hydrofluoric acid with a purity of 99.95% wt. The uncondensed gas is sequentially treated in a sulfuric acid absorption tower and a tertiary water absorption tower to produce a 32.5% wt% fluosilicic acid solution.

[0124] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for the synergistic decomposition of low-grade niobium ore and fluorine-containing ore, characterized in that: The following steps are involved: 1) mixing low-grade niobium ore, fluorine-containing ore and sulfuric acid aqueous solution in a weight ratio of 1:0.1 to 3:2 to 5 to obtain a mixed slurry I; roasting the mixed slurry I at 120 to 350° C. to obtain a roasted ore and a roasting gas; wherein the mass concentration of the sulfuric acid aqueous solution is 50 to 98 wt%; 2) crushing and grinding the roasted ore to obtain roasted ore powder; mixing the roasted ore powder with water in a weight ratio of 0.5 to 15:1 to obtain a mixed slurry II; leaching the mixed slurry II at 20 to 60° C. to obtain a leaching product; and separating the leaching product into a solid and liquid to obtain a leachate and a leaching residue.

2. The method according to claim 1, characterized in that In step 1), the weight ratio of the low-grade niobium ore, the fluorine-containing ore and the sulfuric acid aqueous solution is 1:0.2-2.5:2.5-4.

5.

3. The method according to claim 1, characterized in that In step 1), the calcination temperature is 125-320°C.

4. The method according to claim 1, wherein In step 1), the calcination time is 1 to 8 hours.

5. The method according to claim 1, characterized in that In step 2), the particle size of the roasted ore powder is -100 to -300 mesh.

6. The method according to claim 1, characterized in that In step 2), the weight ratio of the roasted ore powder to water is 1 to 12:

1.

7. The method according to claim 1, characterized in that In step 2), the leaching temperature is 22-55°C.

8. The method according to claim 1, characterized in that In step 2), the leaching time is 0.5 to 5 hours.

9. The method according to claim 1, characterized in that In step 2), stirring is performed during the leaching process, and the stirring speed is 200 to 400 rpm.

10. The method according to claim 1, characterized in that The roasting gas is subjected to condensation recovery and purification treatment in steps to obtain hydrofluoric acid, fluosilicic acid and sulfuric acid.

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