Smelting method for mineral type rare earth ore

Abstract

A smelting method for a mineral-type rare earth ore, which method comprises the following steps: pretreating a mineral-type rare earth ore, and subjecting same to sulfated roasting decomposition, so as to obtain sulfuric acid roasted ore and a tail gas, wherein the pretreatment comprises: mixing the mineral-type rare earth ore, a phosphate and concentrated sulfuric acid; or mechanically activating the mineral-type rare earth ore, and mixing the mechanically activated mineral-type rare earth ore with concentrated sulfuric acid; or mechanically activating the mineral-type rare earth ore, and mixing the mechanically activated mineral-type rare earth ore, a phosphate and concentrated sulfuric acid; leaching the sulfuric acid roasted ore by using a leaching agent, and filtering same to obtain a leachate and leaching slag; and subjecting the leachate to neutralization impurity removal and a solid-liquid separation treatment, so as to obtain a rare earth sulfate solution and neutralization impurity removal slag. By pretreating the mineral-type rare earth ore, the mineral-type rare earth ore is activated and / or pre-decomposed, and then by using a concentrated sulfuric acid roasting method, the rare earth yield can be improved; in addition, material circulation is achieved, and the cost is reduced.

Description

A smelting method for mineral-type rare earth ores

[0001] This invention claims priority to the following patent applications:

[0002] 1. Chinese patent application 202410506195.0, filed on April 25, 2024, entitled "A smelting method for mineral-type rare earth ore";

[0003] 2. Chinese patent application 202410506202.7, filed on April 25, 2024, entitled "A method for mechanically activating and strengthening the decomposition of mineral-type rare earth ores and for smelting and separating them";

[0004] 3. Chinese patent application 202410512327.0, filed on April 26, 2024, entitled "A method for sulfation roasting and decomposition of mineral-type rare earth ores in a weak oxidizing atmosphere";

[0005] 4. Chinese patent application 202410513432.6, filed on April 26, 2024, entitled "A method for decomposing mineral-type rare earth minerals by sulfation roasting after low-temperature roasting and activation". Technical Field

[0006] This invention relates to the field of rare earth metallurgy technology, and in particular to a method for smelting mineral-type rare earth ores. Background Technology

[0007] my country's rare earth resources are mainly mineral-type light rare earth minerals, accounting for more than 90% of the total reserves. The main industrial rare earth minerals are bastnaesite and monazite, with light rare earth content as high as 96% to 98%. The light rare earth deposits with industrial application value are mainly the Bayan Obo rare earth mine in Baotou, the Mianning bastnaesite in Sichuan, and the Weishanhu bastnaesite in Shandong.

[0008] Fluorocarbon cerium ore is commonly treated using an oxidative roasting-hydrochloric acid leaching chemical process. This process is characterized by low investment and low production costs for cerium products. However, it suffers from discontinuous processes. During hydrochloric acid leaching, tetravalent cerium, thorium, and fluorine remain undissolved in the slag. After alkali conversion, fluorine is discharged as sodium fluoride into the wastewater, while thorium and fluorine are dispersed in the slag and wastewater, making recovery difficult and causing environmental pollution. Furthermore, the purity of the cerium product is only 97%–98%, resulting in low value and low rare earth recovery.

[0009] Currently, concentrated sulfuric acid is also used to directly treat fluorocarbon cerium ore. For example, patent CN107475542A discloses a method for treating rare earth concentrate, including: (1) mixing rare earth concentrate with concentrated sulfuric acid to obtain a mixed slurry and a first fluorine-containing gas; (2) mixing the mixed slurry with an initiating liquid for acid hydrolysis to obtain clinker and a second fluorine-containing gas; (3) mixing the clinker with water and then performing leaching to obtain a leaching slurry; (4) performing solid-liquid separation on the leaching slurry to obtain a filtrate and leaching residue, and returning the leaching residue to step (2) for the acid hydrolysis treatment. The above-mentioned concentrated sulfuric acid decomposition method can effectively treat fluorocarbon cerium concentrate, but the decomposition rate of concentrated sulfuric acid is low, fluorocarbon cerium ore is not easily decomposed, acid consumption is high, and impurities such as iron will enter the leaching solution, affecting subsequent separation and purification, and the rare earth yield is low. Summary of the Invention

[0010] The purpose of this invention is to provide a smelting method for mineral-type rare earth ores. By pretreating the mineral-type rare earth ores and then roasting and decomposing them using concentrated sulfuric acid, the rare earth yield of the mineral-type rare earth ores can be improved.

[0011] To address the aforementioned technical problems, embodiments of the present invention provide a method for smelting mineral-type rare earth ores, comprising the following steps:

[0012] S1: Pre-treating mineral-type rare earth ore by sulfation roasting decomposition to obtain sulfuric acid roasted ore and tail gas, wherein the pre-treatment includes:

[0013] Mix the mineral-type rare earth ore, phosphate, and concentrated sulfuric acid; or

[0014] The mineral-type rare earth ore is mechanically activated, and the mechanically activated mineral-type rare earth ore is mixed with concentrated sulfuric acid; or

[0015] The mineral-type rare earth ore is mechanically activated, and the mechanically activated mineral-type rare earth ore, phosphate, and concentrated sulfuric acid are mixed together.

[0016] S2: The sulfuric acid roasted ore is leached with water, a weak acid, or a magnesium-containing solution as the leaching agent, and the leaching solution and leaching residue are obtained by filtration.

[0017] S3: The leachate is subjected to neutralization and impurity removal, and solid-liquid separation treatment to obtain rare earth sulfate solution and neutralization and impurity removal residue.

[0018] Further, in step S1, mixing the mineral-type rare earth ore or mechanically activated mineral-type rare earth ore, phosphate, and concentrated sulfuric acid includes adding phosphate to the mineral-type rare earth ore or mechanically activated mineral-type rare earth ore at a mass ratio of total iron and thorium to total phosphorus of 3 to 5.

[0019] Furthermore, the phosphate includes: apatite and / or monazite.

[0020] Furthermore, in step S2, the magnesium-containing leaching agent in the sulfuric acid roasted ore leaching process includes magnesium bicarbonate solution, and the mass ratio of sulfuric acid roasted ore to leaching agent is 1:5 to 1:20.

[0021] Furthermore, in step S3, an alkaline substance is added to the leachate for neutralization and impurity removal. The alkaline substance includes magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium bicarbonate.

[0022] Furthermore, the rare earth sulfate solution is extracted, transformed, and separated using P507 and / or P204 saponified with magnesium bicarbonate solution to obtain a single rare earth chloride solution and a magnesium-containing solution. The magnesium-containing solution includes magnesium sulfate wastewater, which is treated for recycling leaching or used to prepare magnesium bicarbonate solution.

[0023] Furthermore, the mechanical activation in step S1 includes microwave treatment, with a microwave frequency of 2000MHz to 3000MHz, and the particle size after mechanical activation is D90 < 50μm and D50 < 18μm.

[0024] Furthermore, the preparation process of the magnesium bicarbonate solution includes the following steps:

[0025] Step A: The pH of the magnesium sulfate wastewater generated from rare earth extraction and separation is adjusted to 10.0-12.5 using a calcium-containing alkaline substance to obtain a slurry containing magnesium hydroxide and calcium sulfate.

[0026] Step B involves carbonizing the slurry containing magnesium hydroxide and calcium sulfate using CO2, followed by solid-liquid separation to obtain a magnesium bicarbonate solution and a calcium sulfate byproduct.

[0027] Furthermore, the concentration of the magnesium bicarbonate solution, calculated as MgO, is 5–15 g / L.

[0028] Further, in step S1, the sulfation roasting decomposition includes performing the sulfation roasting decomposition under a weak oxidizing atmosphere to obtain the sulfuric acid roasted ore and the tail gas.

[0029] Further, the weakly oxidizing atmosphere includes: a reducing gas and / or an inert gas; the oxygen content of the weakly oxidizing atmosphere is 0.1% to 15%, preferably 5% to 10%; or, the weakly oxidizing atmosphere includes air, and at least one of the exhaust gas, N2, CO2 and CO.

[0030] Furthermore, the sulfation roasting decomposition temperature is 200℃~450℃, preferably 250℃~350℃; the roasting time is 2h~12h, preferably 3h~5h.

[0031] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0032] 1. By adding a predetermined proportion of phosphate to mineral-based rare earth ores and employing concentrated sulfuric acid roasting, the rare earth yield can be improved. This prevents thorium impurities from entering the aqueous phase, thus avoiding secondary pollution, and allows for wastewater recycling. It also effectively reduces iron leaching. By setting the total iron-thorium / total phosphorus mass ratio in the mineral-based rare earth ores, iron and thorium in the ore are converted into stable thorium pyrophosphate and iron pyrophosphate respectively at a certain temperature, solidifying iron and thorium in the slag. This prevents radioactive thorium from entering the aqueous phase, reduces iron leaching, and increases rare earth yield. Furthermore, it allows for the comprehensive recovery of rare earth elements from low-grade rare earth ores such as apatite.

[0033] 2. By mechanically and microwave-activating mineral-type rare earth ores, the particle size of the minerals is reduced, the formation of new reaction surfaces is promoted, the mineral crystal structure is deformed, and the rare earth phases undergo favorable changes. This helps to fully expose the encapsulated rare earth mineral components, facilitating their contact and reaction with acids, thereby improving their activation performance and achieving a higher rare earth yield. After mechanical and microwave activation, the mineral-type rare earth ores undergo sulfation roasting, converting all rare earth elements in the ores into the easily leached phase RE2(SO4)3. This shortens the processing flow and reduces processing time, contributing to a higher rare earth yield.

[0034] 3. During the sulfation roasting process in a weakly oxidizing atmosphere, all rare earth elements in mineral-type rare earth ores are converted into easily leached RE2(SO4)3 and RE2O3, among which cerium is completely converted into Ce(SO4). x or CeO x (1.5≤x<2), to avoid the formation of stable CeO2 phase and improve rare earth leaching rate. By subjecting mineral-type rare earth ores to sulfation roasting under a weak oxidizing atmosphere, the form of sulfur oxides in the tail gas can be effectively controlled, inhibiting the generation of SO3 gas during sulfation roasting and promoting the generation of SO2 gas. Sulfur in the tail gas mainly exists in the form of SO2, so that SO3 accounts for a larger proportion of the total SO in the tail gas. x The proportion is less than 20%. By sulfation roasting of mineral-type rare earth ores under a weak oxidizing atmosphere, efficient separation and resource recovery of fluorine and sulfur in the tail gas are achieved, while reducing tail gas treatment steps and lowering costs. The tail gas is absorbed by water spray, and HF / SiF4 gas is converted into fluorinated acid, while SO2 gas is further catalytically oxidized to SO3, and then recovered to produce 98wt% concentrated sulfuric acid product. At the same time, the tail gas treatment process reduces the need for pressure filtration, vacuum evaporation and other processes, thus reducing tail gas treatment costs.

[0035] 4. Compared with existing technologies that directly employ sulfation roasting, this invention utilizes a method of first activating the mineral-type rare earth ore with low-temperature roasting followed by sulfation roasting to decompose it. This two-stage temperature control effectively reduces the roasting temperature, time, and acid-to-ore ratio in the sulfation roasting process, increasing the utilization rate of sulfuric acid. This effectively solves problems associated with traditional processes, such as high tail gas production, high sulfur content, severe equipment corrosion and wear, difficulty in separating fluorine from sulfur-containing substances, difficulty in achieving treatment standards, and high operating costs. Before sulfation roasting with concentrated sulfuric acid, the mineral-type rare earth ore is ball-milled to control its particle size within a suitable range. Then, low-temperature roasting is used to activate and / or pre-decompose the ore, generating relatively pure hydrogen fluoride, which is absorbed and recovered using water. The mixed fluorine and sulfur tail gas generated during sulfuric acid roasting is treated by water absorption and separation to recover sulfuric acid and fluorine-containing products, achieving truly low-energy, clean, and environmentally friendly treatment of mineral-type rare earth ore.

[0036] 5. Magnesium sulfate wastewater generated during rare earth separation is neutralized and converted to alkali by adding inexpensive alkaline compounds such as calcium and magnesium. CO2 generated during rare earth extraction and rare earth carbonate roasting is then introduced for carbonization and purification, achieving calcium-magnesium separation and yielding products such as magnesium bicarbonate solution and calcium sulfate gypsum. The magnesium bicarbonate solution is then recycled for use in rare earth smelting and separation processes, achieving water resource recycling. The magnesium bicarbonate solution is mainly used in the leaching, neutralization, and saponification extraction processes of sulfuric acid roasted ores. Electrolytic treatment of rare earth chloride solution prepares rare earth oxide products, and the byproducts hydrogen and chlorine are used to prepare hydrochloric acid, which is then reused in the extraction process, achieving zero-waste production. Attached Figure Description

[0037] Figure 1 is a flowchart of the smelting method for mineral-type rare earth ore provided in an embodiment of the present invention;

[0038] Figure 2 is a flowchart of the smelting method for mineral-type rare earth ore with added phosphate provided in an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of the process logic of the smelting method for mineral-type rare earth ore with added phosphate provided in the embodiment of the present invention;

[0040] Figure 4 is a flowchart of the smelting method for mechanically activated and enhanced decomposition of mineral-type rare earth ores provided in an embodiment of the present invention;

[0041] Figure 5 is a schematic diagram of the process logic of the smelting method for mechanically activated and enhanced decomposition of mineral-type rare earth ores provided in an embodiment of the present invention.

[0042] Figure 6 is a flowchart of a smelting method for sulfation roasting and decomposition of mineral-type rare earth ores under a weak oxidizing atmosphere provided in an embodiment of the present invention.

[0043] Figure 7 is a schematic diagram of the process logic of the smelting method for sulfation roasting and decomposition of mineral-type rare earth ores under a weak oxidizing atmosphere provided in the embodiments of the present invention.

[0044] Figure 8 is a flowchart of a smelting method for low-temperature roasting followed by sulfuric acid roasting of mineral-type rare earth ore provided in an embodiment of the present invention.

[0045] Figure 9 is a schematic diagram of the process logic of the smelting method of mineral-type rare earth ore after low-temperature roasting and activation followed by sulfuric acid roasting, provided in an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0047] Particle size distribution refers to the percentage of particles of different sizes in a powder sample, as reflected by specific instruments and methods. There are two forms: interval distribution and cumulative distribution. Interval distribution, also known as differential distribution or frequency distribution, represents the percentage content of particles within a series of particle size intervals. Cumulative distribution, also called integral distribution, represents the percentage content of particles smaller or larger than a certain particle size.

[0048] D10: The particle size at which the cumulative particle size distribution number of a sample reaches 10%. Physically, it means that 10% of the particles are smaller (or larger) than D10.

[0049] D50: The particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than D50, and 50% are smaller. D50 is also called the median diameter or median particle size. D50 is often used to represent the average particle size of powders.

[0050] D90: The particle size at which the cumulative particle size distribution number of a sample reaches 90%. Physically, it means that 90% of the particles are smaller (or larger) than D90.

[0051] Acid-ore mass ratio: The ratio of the total amount of concentrated sulfuric acid used to the mass of mineral-type rare earth ore; the acid-ore mass ratio described in this invention specifically refers to the mass ratio of concentrated sulfuric acid to concentrate.

[0052] The mineral-type rare earth minerals of this invention include at least one of monazite, bastnaesite, xenotime, and mixed minerals containing bastnaesite.

[0053] First aspect of the present invention

[0054] Referring to Figures 1, 2, and 3, the first aspect of this invention provides a method for smelting mineral-type rare earth ores, comprising the following steps:

[0055] Step S1 involves pretreating the mineral-type rare earth ore by sulfation roasting and decomposition to obtain sulfuric acid roasted ore and tail gas.

[0056] The pretreatment specifically involves mixing mineral-type rare earth minerals, phosphates, and concentrated sulfuric acid. Monazite is a phosphate mineral containing rare earth elements, and the phosphates in this invention include apatite and / or monazite.

[0057] Step S2: Leach the sulfuric acid roasted ore with water, a weak acid, or a magnesium-containing solution, and filter to obtain leachate and leach residue.

[0058] Step S3 involves neutralizing and removing impurities from the leachate, followed by solid-liquid separation to obtain a rare earth sulfate solution and a neutralized residue.

[0059] The technical solution of the first aspect of the present invention addresses the problems existing in the current mineral-type rare earth ore processing technology and proposes a smelting method for mineral-type rare earth ore. By adding phosphate to the mineral-type rare earth ore and using concentrated sulfuric acid roasting, the rare earth yield is improved, the impurity thorium does not enter the aqueous phase, preventing secondary pollution, and the wastewater can be recycled. At the same time, it can effectively reduce the leaching of iron.

[0060] The chemical reactions involved in the sulfuric acid roasting process of mineral-type rare earth ores are as follows: 2REFCO3+3H2SO4=RE2(SO4)3+2HF↑+2CO2↑+2H2O↑; ThO2+2H2SO4=Th(SO4)2+2H2O↑; CaF2+H2SO4=CaSO4↓+2HF↑; SiO2+4HF=SiF4↑+2H2O↑; Fe2O3+H2SO4=Fe2(SO4)3+3H2O↑.

[0061] The reactions that occur in the presence of monazite or apatite are as follows: 2REPO4 + 3H2SO4 = RE2(SO4)3 + 2H3PO4; Ca3(PO4)2 + 3H2SO4 = 2H3PO4 + 3CaSO4↓; 2H3PO4 = H4P2O7↓ + H2O; Th(SO4)2 + H4P2O7 = ThP2O7↓ + 2H2SO4; 2Fe2(SO4)3 + 3H4P2O7 = Fe4(P2O7)3 + 6H2SO4;

[0062] Rare earth sulfuric acid and concentrated sulfuric acid undergo decomposition reactions: RE2(SO4)3=RE2O3+3SO3↑ or RE2(SO4)3=RE2O3+3SO2↑+1.5O2↑; H2SO4=SO3↑+H2O↑.

[0063] Based on the inventor's research on the effects of the presence of monazite or apatite on the smelting of mineral-type rare earth ores, this invention pretreats mineral-type rare earth ores by adding a certain proportion of phosphates, which converts iron and thorium in the mineral-type rare earth ores into ferric pyrophosphate and ferric pyrophosphate respectively and enters the slag. This prevents the radioactive nuclide thorium from entering the aqueous phase, while also reducing iron leaching and increasing the rare earth yield.

[0064] Furthermore, the mass ratio of phosphate to mineral-type rare earth ore is 1 wt% to 10 wt%.

[0065] Furthermore, phosphates are added to mineral-type rare earth ores at a mass ratio of 3 to 5 of total iron and thorium to total phosphorus.

[0066] By setting the mass ratio of total iron and thorium to total phosphorus, iron and thorium in mineral-type rare earth ores can be converted into stable thorium pyrophosphate and iron pyrophosphate respectively at a certain temperature, thus solidifying iron and thorium in the slag. This prevents radioactive nuclides such as thorium from entering the leachate, reduces impurity content, decreases the amount of slag neutralized in the leachate, and improves the rare earth yield. In addition, rare earths contained in monazite can also be recovered.

[0067] Furthermore, in the process of leaching sulfuric acid roasted ore with water circulation, the mass ratio of sulfuric acid roasted ore to water is 1:5 to 1:20; the leaching time is 1h to 6h.

[0068] Furthermore, the concentration of concentrated sulfuric acid is 85wt% to 98wt%; the mass ratio of sulfuric acid to mineral-type rare earth ore is 1:1 to 2:1, preferably 1.2:1 to 1.5:1.

[0069] Furthermore, the roasting temperature for sulfation roasting decomposition is 200℃~450℃, preferably 250℃~350℃; the roasting time for sulfation roasting decomposition is 2h~12h, preferably 3h~5h.

[0070] Mineral-type rare earth ore is decomposed by sulfuric acid roasting to obtain sulfuric acid roasted ore and mixed tail gas; the sulfuric acid roasted ore is then subjected to water leaching, neutralization and impurity removal to obtain water leaching residue and sulfuric acid rare earth solution; the mixed tail gas can be used to prepare 90% sulfuric acid and fluoride products.

[0071] Furthermore, after obtaining the sulfuric acid roasted ore and tail gas in step S1, the process also includes:

[0072] Steps S1-4 involve absorbing and separating the tail gas generated during sulfation roasting to obtain recovered concentrated sulfuric acid and fluorinated acid.

[0073] The sulfur in the exhaust gas mainly exists in the form of SO2 and SO3, while the fluorine mainly exists in the form of HF and SiF4. After absorption and exhaust gas treatment, the sulfur is converted into 90% concentrated sulfuric acid and then recycled. The fluorine is used to prepare fluoride products, thus realizing the recycling of valuable elements in the exhaust gas.

[0074] Specifically, in the neutralization and impurity removal process of step S3, the impurity removal agent added includes at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium bicarbonate.

[0075] Specifically, after obtaining the rare earth sulfate solution and neutralizing and removing impurities in step S3, the process also includes:

[0076] In step S4, the rare earth sulfate solution is extracted and separated using P507 to obtain a single rare earth chloride solution and a magnesium-containing solution. The separated products are single lanthanum chloride, cerium chloride, praseodymium chloride, and neodymium chloride. The magnesium-containing solution is used for cyclic leaching to reduce wastewater discharge. The magnesium-containing solution contains magnesium sulfate wastewater.

[0077] Rare earth carbonates are obtained by precipitation of single rare earth elements, or single rare earth oxides are obtained by calcination.

[0078] Furthermore, the single rare earth chloride solution is subjected to ion-exchange membrane electrolysis to obtain rare earth hydroxide or rare earth oxide products and hydrogen at the cathode, and to generate chlorine at the anode.

[0079] Furthermore, carbon dioxide is introduced into the cathode during the electrolysis process to obtain rare earth carbonate products.

[0080] Hydrogen and chlorine are used to prepare hydrochloric acid, which is then recycled for extraction transformation, organic phase washing in extraction separation processes, and back-extraction.

[0081] The rare earth chloride solution obtained through extraction and separation is electrolyzed to produce hydrogen and chlorine, which are then used to prepare hydrochloric acid. This process enables the recycling of hydrochloric acid during extraction, eliminates the discharge of salt-containing wastewater during production, and saves resources.

[0082] Furthermore, the organic extractant used in the extraction transformation or extraction separation process is P507 and / or P204 saponified with magnesium bicarbonate solution;

[0083] Furthermore, during the electrolysis process, an ion-exchange membrane is used to divide the electrolytic cell into a cathode chamber and an anode chamber; the current density is 500 A / m³. 2 ~8000A / m 2 The tank voltage is 2V to 5V.

[0084] Within the range of current density and cell voltage, efficient electrolysis of rare earth chloride solution can be achieved, avoiding side reactions that affect product quality. At the same time, the electrolysis reaction can be carried out at a lower power consumption, thereby reducing production costs and saving energy.

[0085] Furthermore, leaching is performed using a magnesium bicarbonate solution, the preparation of which includes the following steps:

[0086] Step A: The pH of the magnesium sulfate wastewater generated from rare earth extraction and separation is adjusted to 10.0-12.5 using a calcium-containing alkaline substance to obtain a slurry containing magnesium hydroxide and calcium sulfate.

[0087] Step B involves carbonizing the slurry containing magnesium hydroxide and calcium sulfate using CO2, followed by solid-liquid separation to obtain a magnesium bicarbonate solution and a calcium sulfate byproduct.

[0088] Within a pH range of 10.0 to 12.5, it can be ensured that calcium-containing alkaline substances can more fully convert magnesium sulfate into magnesium hydroxide and calcium sulfate, avoiding incomplete reactions that could lead to unstable concentrations.

[0089] Furthermore, the concentration of the magnesium bicarbonate solution, calculated as MgO, is 5–15 g / L.

[0090] Within the specified concentration range of magnesium bicarbonate solution, magnesium bicarbonate can be made more stable and can fully react with organic extractants under the corresponding concentration conditions, reducing resource waste.

[0091] In this invention, magnesium sulfate wastewater and carbon dioxide generated during the smelting and separation process are recycled to prepare magnesium bicarbonate solution for leaching and saponifying organic extractants. Combined with electrolytic treatment of rare earth chloride solution obtained from extraction transformation and extraction separation, the invention achieves the recycling of magnesium, carbon dioxide, water and hydrochloric acid during the rare earth ore smelting and separation process, thus realizing zero-waste production.

[0092] The first aspect of the technical solution of the present invention will be further described below with reference to several comparative examples and embodiments:

[0093] Comparative Example 1-1

[0094] A. The concentrate mixed with concentrated sulfuric acid is matured at a temperature of 40℃~180℃; B. The matured concentrate is roasted for 1~8 hours at a roasting temperature of 180℃~330℃; C. The roasted ore produced by roasting is leached with water to leach rare earth elements and thorium into the solution. Thorium and rare earth elements are then separated by extraction, followed by washing and back-extraction to obtain thorium nitrate product; after thorium extraction, the solution precipitates to obtain a thorium-free rare earth product. In Comparative Example 1, the impurity thorium requires further processing, which incurs additional costs.

[0095] Comparative Examples 1-2

[0096] The residue from the second-grade or mixed residue of the first-grade and second-grade residues is washed with an aqueous solution of pH 2-4 until the chloride ion weight percentage concentration is less than 0.1%. Then, it is leached with sulfuric acid to obtain a rare earth sulfate solution and filter residue. The rare earth sulfate solution is extracted and separated, and the supported organic phase is then washed with a mixed solution of aluminum sulfate and nitric acid or aluminum nitrate to obtain rare earth compounds, fluoride washing solution, pure cerium product, and thorium product. The fluoride-containing alkaline wastewater and fluoride washing solution obtained from the alkali conversion are used to synthesize fluoride products. In Comparative Example 2, fluorine entering the rare earth sulfate solution easily forms fluoride precipitates, affecting the water leaching and extraction processes.

[0097] Example 1-1

[0098] Mineral-type rare earth ore was uniformly mixed with 90wt% sulfuric acid and then roasted with sulfuric acid. The mass ratio of concentrated sulfuric acid to mineral-type rare earth ore was 1.3:1. The roasting temperature was 300℃ and the roasting time was 3 hours. The resulting product was sulfuric acid-roasted ore. The sulfuric acid-roasted ore was then leached with water at a mass ratio of 1:10 for 3 hours to obtain a water leachate. The rare earth recovery rate was 90.5%.

[0099] The obtained sulfuric acid roasted ore is leached with circulating water. The leachate is neutralized, impurities are removed, and solid-liquid separation is performed to obtain a rare earth sulfuric acid solution and leaching residue. The tail gas generated during the sulfuric acid roasting process is absorbed, separated, and post-treated to obtain recovered concentrated sulfuric acid and fluorine-containing products.

[0100] Examples 1-2

[0101] A mixture of 8 wt% apatite and 90 wt% sulfuric acid was prepared by adding mineral-type rare earth ore to a homogeneous solution and then roasting it with sulfuric acid. The iron + thorium / phosphorus mass ratio was maintained at 3, and the mass ratio of concentrated sulfuric acid to mineral-type rare earth ore was 1.3:1. The roasting temperature was 300℃, and the roasting time was 3 hours. The resulting sulfuric acid-roasted ore was then subjected to water leaching at a mass ratio of 1:10 for 3 hours, yielding a leachate with a rare earth recovery rate of 94.1%.

[0102] The obtained sulfuric acid roasted ore is leached with circulating water. The leachate is neutralized, impurities are removed, and solid-liquid separation is performed to obtain a rare earth sulfuric acid solution and leaching residue. The tail gas generated during the sulfuric acid roasting process is absorbed, separated, and post-treated to obtain recovered concentrated sulfuric acid and fluorine-containing products.

[0103] Examples 1-3

[0104] A mineral-type rare earth ore was mixed with 15 wt% apatite and 90 wt% sulfuric acid, then roasted with sulfuric acid to ensure an iron + thorium (I+T) / phosphorus mass ratio of 3 and a sulfuric acid to mineral-type rare earth ore mass ratio of 1.3:1. The roasting temperature was 300℃ and the roasting time was 3 hours, yielding sulfuric acid-roasted ore. The roasted ore was then leached with water at a mass ratio of 1:10 for 3 hours to obtain a leachate with a rare earth recovery rate of 95.3%.

[0105] The obtained sulfuric acid roasted ore is leached with circulating water. The leachate is neutralized, impurities are removed, and solid-liquid separation is performed to obtain a rare earth sulfuric acid solution and leaching residue. The tail gas generated during the sulfuric acid roasting process is absorbed, separated, and post-treated to obtain recovered concentrated sulfuric acid and fluorine-containing products.

[0106] Table 1 Examples

[0107] The first aspect of this invention aims to protect a smelting method for mineral-type rare earth ores, comprising the following steps: mixing mineral-type rare earth ores, phosphates, and concentrated sulfuric acid, and performing sulfation roasting decomposition to obtain sulfuric acid roasted ore and tail gas, wherein the phosphates include: apatite and / or monazite; leaching the sulfuric acid roasted ore with circulating water to obtain a leachate; and neutralizing, removing impurities, and separating the solid and liquid components in the leachate to obtain a rare earth sulfate solution and leaching residue. The above technical solution has the following advantages:

[0108] 1. By adding a predetermined proportion of phosphate to mineral-type rare earth ore and using concentrated sulfuric acid roasting, the rare earth yield can be improved, which can prevent the impurity thorium from entering the aqueous phase, thus preventing secondary pollution. The wastewater can be recycled, and the leaching of iron can be effectively reduced.

[0109] 2. In mineral-type rare earth ores, phosphate is added at a mass ratio of 1wt% to 10wt% of the mineral-type rare earth ore, and at a mass ratio of total iron and thorium to total phosphorus of 3 to 5. This allows the iron and thorium in the ore to be converted into stable thorium pyrophosphate and iron pyrophosphate respectively at a certain temperature, thus solidifying the iron and thorium in the slag. This prevents radioactive nuclides such as thorium from entering the leachate, reduces the impurity content, decreases the amount of slag in the leachate, and improves the rare earth yield. In addition, the rare earth contained in monazite can also be recovered.

[0110] Second aspect of the invention

[0111] Referring to Figures 1, 4, and 5, a second aspect of the present invention provides a method for smelting mineral-type rare earth ores, comprising the following steps:

[0112] Step S1 involves pretreating the mineral-type rare earth ore by sulfation roasting and decomposition to obtain sulfuric acid roasted ore and tail gas.

[0113] The preprocessing includes:

[0114] The mineral-type rare earth ore is added to a grinding equipment and mechanically activated under microwave action; the mechanically activated mineral-type rare earth ore is mixed with a certain proportion of concentrated sulfuric acid and then subjected to sulfation roasting decomposition to obtain sulfation roasted ore, and the tail gas generated during roasting is treated.

[0115] Step S2: Leach the sulfuric acid roasted ore with water, weak acid or magnesium-containing solution as leaching agent, and filter to obtain leaching solution and leaching residue;

[0116] Step S3: The leachate is neutralized and purified, and then subjected to solid-liquid separation to obtain rare earth sulfate solution and neutralized residue.

[0117] In step S1, mechanical activation utilizes mechanical actions such as grinding, compression, shearing, and impact to alter the physical properties of mineral particles and disrupt their crystal structure. Mechanical grinding not only changes the macroscopic morphology, particle size, and specific surface area of ​​mineral particles but also disrupts their crystal structure, such as causing lattice distortion and increased disorder, thereby enhancing their activation performance and reducing the requirements for reaction conditions such as temperature and solution dosage. The mechanical energy input through mechanical force can induce some chemical reactions that cannot be induced by heat energy, and the reaction conditions and processes are easily achieved, thus effectively addressing the issue of energy and resource conservation.

[0118] Microwaves enable efficient and rapid heating and are widely used in chemical and mineral processing fields. They help accelerate chemical reaction rates and change product properties. Mechanical activation under microwave action can cause mineral components to vibrate rapidly. Due to the different microwave absorption capabilities of minerals, the heating rates are different. Cracks are generated between different minerals due to thermal stress, thereby exposing the encapsulated and impregnated minerals and changing the specific surface area and pore structure of mineral particles, thus improving the reactivity.

[0119] By mechanically and microwaveally activating mineral-type rare earth ores, the particle size of the minerals is reduced, the formation of new reaction surfaces is promoted, the mineral crystal structure is deformed, and the rare earth phase undergoes favorable changes. This helps to fully expose the encapsulated rare earth mineral components, making them easier to contact and react with acids, thereby improving their activation performance and achieving a higher rare earth yield.

[0120] Mineral-type rare earth minerals include one or more of the following: bastnaesite, monazite, xenotime, and mixed rare earth minerals.

[0121] In steps S2 and S3 of the second aspect of the present invention, the obtained sulfated roasted ore is leached with magnesium bicarbonate solution, neutralized to remove impurities, and separated into solid and liquid components to obtain rare earth sulfate solution and leaching residue.

[0122] Furthermore, the frequency of the microwave in step S1 is 2000MHz to 3000MHz.

[0123] Within the specified frequency range, rapid heating of the raw materials helps to quickly generate cracks in the mineral-type rare earth mineral particles and change their crystal structure, thereby exposing the encapsulated and impregnated minerals and improving their reactivity.

[0124] Furthermore, the particle size after mechanical activation is D90 < 50 μm and D50 < 18 μm.

[0125] Mechanically activating mineral-type rare earth ores to the specified particle size range helps to fully expose the mineral components, facilitating subsequent sulfation roasting and decomposition, and improving the rare earth yield.

[0126] Furthermore, the concentration of concentrated sulfuric acid used in the sulfation roasting decomposition is greater than 90 wt%, the mass ratio of the concentrated sulfuric acid to the mineral-type rare earth ore is 1.0 to 2.0, the sulfation roasting temperature is 150 to 400°C, and the roasting time is 1.0 to 8.0 h.

[0127] Preferably, the mass ratio of concentrated sulfuric acid to mineral-type rare earth ore is 1.2 to 1.5, the roasting temperature is 180 to 350°C, and the roasting time is 2.0 to 5.0 h.

[0128] Within the specified mass ratio of concentrated sulfuric acid to mineral-type rare earth ore, roasting temperature, and roasting time, the mineral components can fully react with sulfuric acid and be converted into rare earth sulfate. Within the specified preferred conditions, the reaction efficiency can be improved more effectively, sulfuric acid decomposition can be reduced, and energy consumption can be reduced, thereby effectively reducing production costs.

[0129] Furthermore, the exhaust gas generated during roasting contains SO2, SO3, HF, and SiF4, which are absorbed by water spray, distilled, and separated to recover sulfuric acid and fluorine-containing products.

[0130] Furthermore, the rare earth content in the sulfuric acid rare earth solution, calculated as REO, is 10–45 g / L.

[0131] Within the specified rare earth sulfate concentration range, sufficient leaching of rare earth sulfate can be ensured, thereby guaranteeing the rare earth yield.

[0132] Furthermore, the rare earth solution obtained in step S3 is subjected to extraction transformation or extraction separation using an organic extractant to obtain a single or mixed rare earth chloride solution.

[0133] Furthermore, the single or mixed rare earth chloride solution is subjected to ion-exchange membrane electrolysis to obtain rare earth hydroxide or rare earth oxide products and hydrogen gas at the cathode, and to generate chlorine gas at the anode.

[0134] Furthermore, during the electrolysis process, carbon dioxide is introduced into the cathode to obtain rare earth carbonate products.

[0135] The hydrogen and chlorine are used to prepare hydrochloric acid, which is then reused in extraction transformation, organic phase washing, and back-extraction during extraction separation processes.

[0136] The rare earth chloride solution obtained through extraction and separation is electrolyzed to produce hydrogen and chlorine, which are then used to prepare hydrochloric acid. This process enables the recycling of hydrochloric acid during extraction, eliminates the discharge of salt-containing wastewater during production, and saves resources.

[0137] Furthermore, the organic extractant used in the extraction transformation or extraction separation process is P507 and / or P204 saponified with magnesium bicarbonate solution;

[0138] The rare earth content in the single or mixed rare earth chloride solution is 200-300 g / L.

[0139] Furthermore, during the electrolysis process, an ion exchange membrane is used to divide the electrolytic cell into a cathode chamber and an anode chamber; the current density is 500 A / m³. 2 ~8000A / m 2 The tank voltage is 2V to 5V.

[0140] Within the specified current density and cell voltage range, efficient electrolysis of rare earth chloride solution can be achieved, avoiding side reactions that could affect product quality. At the same time, the electrolysis reaction can be carried out at a lower power consumption, thereby reducing production costs and saving energy.

[0141] Furthermore, in step S2, leaching is performed using water, a weak acid, or a magnesium-containing solution, specifically using a magnesium bicarbonate solution. The preparation process of the magnesium bicarbonate solution includes the following steps:

[0142] Step A: The pH of the magnesium sulfate wastewater generated from rare earth extraction and separation is adjusted to 10.0-12.5 using a calcium-containing alkaline substance to obtain a slurry containing magnesium hydroxide and calcium sulfate.

[0143] Step B involves carbonizing the slurry containing magnesium hydroxide and calcium sulfate using CO2, followed by solid-liquid separation to obtain a magnesium bicarbonate solution and a calcium sulfate byproduct.

[0144] Within the specified pH range, it can be ensured that calcium-containing alkaline substances can more fully convert magnesium sulfate into magnesium hydroxide and calcium sulfate, avoiding incomplete reactions that could lead to unstable concentrations.

[0145] Furthermore, the concentration of the magnesium bicarbonate solution, calculated as MgO, is 5–15 g / L.

[0146] Within the specified concentration range of magnesium bicarbonate solution, magnesium bicarbonate can be made more stable and can fully react with organic extractants under the corresponding concentration conditions, reducing resource waste.

[0147] Rare earth products are at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium.

[0148] The following is a detailed description of the above-mentioned method for mechanically activating and strengthening the decomposition of mineral-type rare earth ores and for smelting and separating them, using a complete implementation process:

[0149] (1) Add mineral-type rare earth ore to the grinding equipment and mechanically activate it under microwave action of 2000MHz~3000MHz until the particle size reaches D90<50μm and D50<18μm. Then, perform sulfation roasting decomposition to obtain sulfation roasted ore.

[0150] (2) The concentration of concentrated sulfuric acid used is greater than 90wt%, the amount of concentrated sulfuric acid used is 1.2 to 1.5 times the mass of mineral rare earth ore, the temperature of sulfation roasting is 180 to 350℃, and the roasting time is 2.0 to 5.0h; all rare earth elements in mineral rare earth ore are converted into easily leached phase RE2(SO4)3.

[0151] (3) The sulfated roasted ore is leached with a magnesium bicarbonate solution with a concentration of 5-15 g / L, neutralized to remove impurities, and separated into solid and liquid to obtain a rare earth sulfate solution and leaching residue.

[0152] (4) The mixed tail gas generated during the sulfation roasting process is treated by the tail gas absorption system to obtain concentrated sulfuric acid and fluorosilicic acid products with a concentration greater than 90wt%.

[0153] (5) The rare earth sulfate solution is extracted and / or separated by using P507 and / or P204 saponified with magnesium bicarbonate at a concentration of 5-15 g / L to obtain a rare earth chloride solution with a concentration of 200-300 g / L.

[0154] (6) The rare earth chloride solution is subjected to a current density of 500–8000 A / m 2 Electrolysis is performed under a cell voltage of 2-5V to obtain rare earth hydroxide or rare earth oxide products; or carbon dioxide is introduced into the cathode to obtain rare earth carbonate products.

[0155] (7) Use calcium-containing alkaline substances to convert magnesium sulfate wastewater generated during extraction separation and / or extraction transformation to obtain a slurry containing magnesium hydroxide and calcium sulfate. Use CO2 recovered from the smelting separation process to carbonize the slurry containing magnesium hydroxide and calcium sulfate. After solid-liquid separation, obtain magnesium bicarbonate solution and calcium sulfate slag with a concentration of 5-15 g / L.

[0156] The method flow and technical effects of the second aspect of the present invention will be further described below with reference to several embodiments:

[0157] Example 2-1

[0158] 1000g of bastnaesite was added to a ball mill and mechanically activated under microwave irradiation at a frequency of 2450MHz. The activated bastnaesite had particle sizes of D50 < 10μm and D90 < 30μm. It was mixed with 1200g of concentrated sulfuric acid (98wt%) and placed in a roasting kiln for roasting at 150℃ for 3 hours. Leaching was performed using 38L of water and 2.4L of a 6.5g / L (calculated as MgO) magnesium bicarbonate solution, followed by acid adjustment. The rare earth leaching rate was 94.9%. P507 was saponified using the 6.5g / L magnesium bicarbonate solution. The saponified organic compound was then used for extraction and separation of rare earth sulfate solution to obtain a 280g / L rare earth chloride solution. The solution was then processed at a current density of 1000A / m². 2 Electrolysis was performed at a cell voltage of 2V. The rare earth hydroxide produced after electrolysis was filtered, washed, dried, and calcined to obtain rare earth oxide products. The total rare earth yield was 93.0%. The hydrogen gas generated at the cathode and the chlorine gas generated at the anode were collected and prepared into 31% hydrochloric acid for washing and back-extraction.

[0159] Example 2-2

[0160] 1000g of bastnaesite was added to a ball mill and mechanically activated under microwave irradiation at a frequency of 2450MHz. The activated mixed rare earth ore had particle sizes of D50 < 18μm and D90 < 50μm. This was mixed with 1500g of concentrated sulfuric acid (98wt%) and placed in a roasting kiln for 1 hour at 400℃. Leaching was then performed using 36L of water and 4.3L of a 6.5g / L magnesium bicarbonate solution, followed by acid adjustment. The rare earth leaching rate was 93.2%. P507 was saponified using the 6.5g / L magnesium bicarbonate solution. The saponified organic compound was then used for extraction and separation from the rare earth sulfate solution, yielding a 280g / L rare earth chloride solution. The solution was then processed at a current density of 4000A / m³. 2 Electrolysis was performed at a cell voltage of 3V, with carbon dioxide gas introduced at the cathode. The rare earth carbonate produced after electrolysis was filtered, washed, dried, and calcined to obtain rare earth oxide products. The total rare earth yield was 91.1%. The hydrogen gas produced at the cathode and the chlorine gas produced at the anode were collected and prepared into 31% hydrochloric acid for washing and back-extraction.

[0161] Example 2-3

[0162] 1000g of xenotime ore was added to a ball mill and mechanically activated under microwave irradiation at a frequency of 2450MHz. The activated xenotime ore had a particle size of D50 < 5μm and D90 < 10μm. It was mixed with 1400g of concentrated sulfuric acid (98wt%) and placed in a roasting kiln. Roasting was carried out at 200℃ for 2 hours. Leaching was performed using 37L of water and 3.7L of a 6.5g / L magnesium bicarbonate solution, followed by acid adjustment. The rare earth leaching rate was 95.1%. P507 was saponified using the 6.5g / L magnesium bicarbonate solution. The saponified organic compound was then used for extraction and separation of rare earth sulfate solution to obtain a 280g / L rare earth chloride solution. This solution was then processed at 75℃ and a current density of 6000A / m. 2 Electrolysis was performed at a cell voltage of 4V. The precipitate produced after electrolysis was filtered, washed, dried, and calcined to obtain rare earth oxide products. The total rare earth yield was 92.9%. The hydrogen gas generated at the cathode and the chlorine gas generated at the anode were collected and prepared into 31% hydrochloric acid for washing and back-extraction.

[0163] Detailed implementation data of other embodiments 1-31 of the second aspect of the present invention are shown in Table 2.

[0164] Table 2

[0165] Based on the embodiments of the second aspect described above, the following conclusions can be drawn:

[0166] The second aspect of this invention involves mechanically and microwave activating mineral-type rare earth ores to reduce the particle size of the minerals, promote the formation of new reaction surfaces, deform the mineral crystal structure, and cause favorable changes in the rare earth phases. This helps to fully expose the encapsulated rare earth mineral components, making them easier to contact and react with acids, thereby improving their activation performance and achieving a higher rare earth yield.

[0167] The method described in the second aspect of this invention for processing fluorocarbon cerium rare earth concentrate can effectively shorten the process flow and reduce processing time. While ensuring a high rare earth yield, it can effectively reduce the amount of acid and alkali used, thereby significantly reducing production costs. The washing water is used for hydrochloric acid dilution, which can ensure an increased rare earth yield and effectively reduce wastewater discharge.

[0168] Furthermore, the second aspect of the present invention provides a smelting method for mineral-type rare earth ore. In step S1, when pretreating the mineral-type rare earth ore, the pretreatment includes: adding the mineral-type rare earth ore into a grinding equipment, mechanically activating it under microwave action, mixing the mechanically activated mineral-type rare earth ore, phosphate and concentrated sulfuric acid, leaching with magnesium bicarbonate solution, and obtaining rare earth sulfate solution and leaching residue after neutralization, impurity removal and solid-liquid separation.

[0169] Mechanical activation, especially microwave activation, can enhance the reactivity of minerals and lower the reaction energy barrier. This makes the chemical reaction between microwave-activated mineral rare earth minerals, phosphates, and concentrated sulfuric acid easier to carry out. It can effectively improve roasting efficiency, reduce reaction time and temperature, reduce production energy consumption and costs, effectively increase rare earth yield, and convert iron and thorium in the ore into stable thorium pyrophosphate and iron pyrophosphate at a certain temperature, respectively, solidifying iron and thorium in the slag and preventing the radioactive nuclide thorium from entering the aqueous phase.

[0170] Examples 2-4

[0171] 1000g of bastnaesite was added to a ball mill and mechanically activated under microwave irradiation at a frequency of 2450MHz. The activated bastnaesite had a particle size of D50 < 10μm and D90 < 30μm. 15wt% apatite was added, and the mixture was thoroughly mixed with 1200g of concentrated sulfuric acid (98wt%). The mixture was then calcined with sulfuric acid, ensuring a (iron + thorium) / phosphorus mass ratio of 3. The mixture was placed in a calcining kiln and calcined at 150℃ for 3 hours. Leaching was performed using 38L of water and 2.4L of a 6.5g / L (calculated as MgO) magnesium bicarbonate solution, followed by acid adjustment. The rare earth leaching rate was 95.9%. P507 was saponified using the 6.5g / L magnesium bicarbonate solution. The saponified organic solvent was then used for extraction and separation of the rare earth sulfate solution, yielding a 280g / L rare earth chloride solution. The solution was then processed at a current density of 1000A / m². 2 Electrolysis was performed at a cell voltage of 2V. The rare earth hydroxide produced after electrolysis was filtered, washed, dried, and calcined to obtain rare earth oxide products. The total rare earth yield was 94.2%. The hydrogen gas generated at the cathode and the chlorine gas generated at the anode were collected and prepared into 31% hydrochloric acid for washing and back-extraction.

[0172] For detailed implementation data of other embodiments 32-62 of the second aspect of the present invention, please refer to Table 3.

[0173] Table 3

[0174] Based on the examples of mechanical microwave activation and mixing with phosphate and concentrated sulfuric acid as described in the second aspect above, the following conclusions can be drawn:

[0175] Mechanical activation, especially microwave activation, can enhance the reactivity of minerals and lower the reaction energy barrier. This makes the chemical reaction between microwave-activated mineral rare earth minerals, phosphates, and concentrated sulfuric acid easier to carry out. It can effectively improve roasting efficiency, reduce reaction time and temperature, reduce production energy consumption and costs, effectively increase rare earth yield, and convert iron and thorium in the ore into stable thorium pyrophosphate and iron pyrophosphate at a certain temperature, respectively, solidifying iron and thorium in the slag and preventing the radioactive nuclide thorium from entering the aqueous phase.

[0176] Third aspect of the invention

[0177] Referring to Figures 1, 6, and 7, a third aspect of the present invention provides a method for smelting mineral-type rare earth ores, comprising the following steps:

[0178] Step S1 involves pretreating the mineral-type rare earth ore by sulfation roasting and decomposition to obtain sulfuric acid roasted ore and tail gas.

[0179] Preprocessing includes:

[0180] Mix mineral-type rare earth minerals, phosphates, and concentrated sulfuric acid; or

[0181] Mineral-type rare earth ore is added to a grinding equipment and mechanically activated under microwave irradiation. The mechanically activated mineral-type rare earth ore is then mixed with concentrated sulfuric acid; or

[0182] Mineral-type rare earth ore is added to a grinding equipment and mechanically activated under microwave action. The mechanically activated mineral-type rare earth ore, phosphate, and concentrated sulfuric acid are then mixed.

[0183] The sulfation roasting decomposition is specifically carried out under a weak oxidizing atmosphere to obtain the sulfuric acid roasted ore and the tail gas.

[0184] Specifically, the weakly oxidizing atmosphere includes: reducing gases and / or inert gases; wherein the oxygen content is 0.1% to 15%, preferably 5% to 10%.

[0185] Furthermore, the weakly oxidizing atmosphere includes air, and also includes at least one of the exhaust gas, N2, CO2 and CO.

[0186] Step S2 involves leaching the roasted ore obtained in S1 with water, a weak acid, or a magnesium-containing solution as the leaching agent, and then filtering to obtain the leachate and leaching residue.

[0187] Step S3 involves neutralizing and removing impurities from the leachate obtained in S2, followed by solid-liquid separation to obtain a rare earth sulfate solution and a neutralized residue.

[0188] During the sulfation roasting process in a weakly oxidizing atmosphere, mineral-type rare earth ores decompose into RE2(SO4)3, simultaneously generating tail gases such as HF, SiF4, CO2, and water vapor. The specific reactions are as follows: 2REFCO3 + 3H2SO4 = RE2(SO4)3 + 2HF↑ + 2CO2↑ + 2H2O↑; 3REFCO3 = RE2O3 + REF3 + CO2↑; RE2O3 + 3H2SO4 = RE2(SO4)3 + 3H2O↑; CaF2 + H2SO4 = CaSO4↓ + 2HF↑; SiO2 + 4HF = SiF4↑ + 2H2O↑.

[0189] Rare earth sulfuric acid and concentrated sulfuric acid each decompose to produce SO2, SO3 and H2O vapors as tail gases. The specific reactions are as follows: RE2(SO4)3=RE2O3+3SO3↑ or RE2(SO4)3=RE2O3+3SO2↑+1.5O2↑; H2SO4=SO3↑+H2O↑;

[0190] Under a weak oxidizing atmosphere (such as CO), the decomposition of rare earth sulfuric acid and concentrated sulfuric acid inhibits the production of SO3 gas and promotes the production of SO2 gas. The specific reactions are as follows: Ce2(SO4)3+3CO=Ce2O3+3SO2+3CO2; H2SO4+CO=SO2+CO2+H2O;

[0191] Under a weak oxidizing atmosphere (when oxygen is insufficient), the further oxidation of Ce2(SO4)3 and Ce2O3 to Ce(SO4)2 and CeO2 is inhibited, while the formation of Ce(SO4)2 is promoted. x CeO x (1.5≤x<2), the specific reaction is as follows: Ce2O3+(x-1.5)O2=2CeO x (1.5≤x<2); Ce2(SO4)3+O2(less)→2Ce(SO4) x (1.5≤x<2).

[0192] The third aspect of the present invention involves a sulfation roasting process under a weak oxidizing atmosphere, in which all rare earth elements in mineral-type rare earth ores are converted into easily leached RE2(SO4)3 and RE2O3, wherein cerium is completely converted into Ce(SO4). x or CeO x (1.5≤x<2), to avoid the formation of stable phase CeO2, the proportion of Ce(IV) in total Ce is less than 3%.

[0193] Currently, conventional processes produce exhaust gases containing over 50% SO3. Both SO3 and HF / SiF4 are readily soluble in water and difficult to separate. After water spray absorption, SO3 is converted into sulfuric acid and fluorine-containing acids. Further pressure filtration and reduced-pressure evaporation yield 70wt% concentrated sulfuric acid, while the gas phase is recovered via condensation to obtain fluorine-containing acids. SO2, however, has low solubility in water and is more easily separated from HF / SiF4 during water spray absorption. The present invention addresses this issue by subjecting mineral-type rare earth ores to sulfation roasting under a weak oxidizing atmosphere. This effectively controls the form of sulfur oxides in the exhaust gas, achieving efficient separation and resource recovery of fluorine and sulfur. Controlling the oxygen content reduces the SO3 content in the exhaust gas, ensuring that SO3 constitutes a smaller proportion of the total SO3 content. x The proportion is less than 20%, preferably 10%, so that the sulfur element in the tail gas mainly exists in the form of SO2, which promotes the separation of fluorine and sulfur in the tail gas and their conversion into valuable by-products. It can also reduce the cerium oxidation rate and increase the leaching rate.

[0194] Preferably, the roasting temperature range for sulfation roasting decomposition under a weak oxidizing atmosphere is 250℃~350℃; the roasting time for sulfation roasting decomposition under a weak oxidizing atmosphere is 3h~5h. Preferably, the concentration of concentrated sulfuric acid used for sulfation roasting decomposition under a weak oxidizing atmosphere is 90wt%~98wt%. Further, the acid-ore mass ratio in the sulfation roasting decomposition process under a weak oxidizing atmosphere is 1.0~2.0, preferably 1.2~1.5. In the mineral-type rare earth ore, all rare earth elements are converted into easily leached phases RE2(SO4)3 and RE2O3, wherein Ce(IV) accounts for less than 3% of the total Ce, improving the total rare earth yield; sulfur elements in the mixed tail gas are converted into SO2, so that SO3 accounts for a small proportion of the total SO2 in the tail gas. x The proportion is less than 20%. The mixed tail gas is absorbed and post-treated to obtain concentrated sulfuric acid for reuse in the sulfation roasting process, and the fluorinated acid is treated to obtain fluoride products.

[0195] Furthermore, the leaching treatment time for the roasted ore is 1h to 6h; the mass ratio of roasted ore to leaching agent is 1:5 to 1:20.

[0196] Furthermore, the neutralization and impurity removal process employs at least one of magnesium hydroxide, magnesium carbonate, magnesium oxide, and magnesium bicarbonate.

[0197] In addition, the exhaust gas includes at least two of the following: SO2, SO3, water vapor, HF, and SiF4, with SO3 accounting for a significant portion of the total SO2 content. x If the proportion is less than 20%, the tail gas is absorbed and separated to obtain recovered concentrated sulfuric acid and fluorine-containing acid. The concentrated sulfuric acid is returned to the sulfuric acid roasting process, and the fluorine-containing acid is treated to obtain fluoride products. At the same time, the rare earth sulfuric acid solution obtained from S3 is transformed and separated by P507 extraction to obtain a single rare earth chloride solution and a magnesium-containing solution. The magnesium-containing solution is recycled for leaching.

[0198] By performing a sulfation roasting process under a weak oxidizing atmosphere, the sulfide form in the exhaust gas is controlled to be SO2 gas, thereby controlling the chemical composition of the exhaust gas to gases such as SO2 / HF / SiF4. Sulfur in the exhaust gas mainly exists in the form of SO2, making SO3 the majority of the total SO2 content. x The proportion is less than 20%, preferably 10%. After water spray absorption, HF / SiF4 gas is converted into fluorinated acid, while SO2 gas enters the subsequent treatment process to be converted into 98wt% concentrated sulfuric acid product.

[0199] The technical solution of the third aspect of the present invention will be further described below with reference to comparative examples and several embodiments:

[0200] Comparative Example 3-1

[0201] (1) The mineral-type rare earth ore was decomposed by sulfation roasting in air atmosphere to obtain roasted ore; the concentration of concentrated sulfuric acid used was 90wt%, the acid-ore ratio was 1.5, the roasting conditions were 350℃, and the roasting time was 4h; most of the rare earth elements in the mineral-type rare earth ore were converted into RE2(SO4)3 and RE2O3, of which Ce(IV) accounted for more than 3% of the total Ce.

[0202] (2) The obtained sulfated roasted ore was leached with water, filtered to obtain leachate and leaching residue. The roasted ore and water were leached together at a mass ratio of 1:10 for 1 hour. The leachate was neutralized and impurities removed, and solid-liquid separation was performed to obtain rare earth sulfate solution and neutralized residue. The rare earth yield was approximately 92%.

[0203] (3) The SO3 content in the mixed tail gas of the sulfation roasting process accounts for a significant portion of the total SO3 content. x The proportion of sulfuric acid is greater than 50%. The mixed tail gas is absorbed and post-treated to obtain 70wt% concentrated sulfuric acid and 98wt% concentrated sulfuric acid. The mass ratio of the two is about 1:1. The 90wt% sulfuric acid is prepared and recycled for the sulfation roasting process. Fluoride-containing acid is treated to obtain fluoride products.

[0204] Example 3-1

[0205] (1) The mineral-type rare earth ore is subjected to sulfation roasting decomposition in an atmosphere of at least one or more of the following gases: air and tail gas, N2, CO2 and CO, to obtain roasted ore; the concentration of concentrated sulfuric acid used is 85-98 wt%, the acid-to-ore ratio is 1.0-2.0 times, the roasting conditions are 200-450℃, and the roasting time is 2-12 h; all rare earth elements in the mineral-type rare earth ore are converted into easily leached phases RE2(SO4)3 and RE2O3, wherein Ce(IV) accounts for less than 3% of the total Ce.

[0206] (2) The obtained sulfation roasted ore under a weak oxidizing atmosphere is leached with water, a weak acid, or a magnesium-containing solution. The leaching solution and leaching residue are obtained by filtration. The roasted ore and leaching agent are leached at a mass ratio of 1:5 to 1:20 for 1 to 6 hours. The leaching solution is neutralized and impurities are removed, and solid-liquid separation is performed to obtain a rare earth sulfate solution and a neutralized and impurity-removed residue. The rare earth yield is greater than 95%.

[0207] (3) The sulfur in the mixed tail gas of the weak oxidizing atmosphere sulfation roasting process is converted into SO2, so that SO3 accounts for a larger proportion of the total SO in the tail gas. x The proportion is less than 20%. The mixed tail gas is absorbed and post-treated to obtain 98wt% concentrated sulfuric acid, which is recycled in the sulfation roasting process. The fluorinated acid is treated to obtain fluoride products.

[0208] Other embodiments, comparative conditions, and technical effects of the third aspect are detailed in Table 4.

[0209] Table 4

[0210] The third aspect of this invention aims to protect a method for sulfation roasting and decomposing mineral-type rare earth ores in a weakly oxidizing atmosphere, comprising the following steps: S1: mixing the mineral-type rare earth ores with concentrated sulfuric acid, and performing sulfation roasting and decomposition under a weakly oxidizing atmosphere to obtain roasted ore and tail gas; S2: leaching the roasted ore obtained in S1 with water, a weak acid, or a magnesium-containing solution as a leaching agent, and filtering to obtain a leachate and a leaching residue; S3: subjecting the leachate obtained in S2 to neutralization, impurity removal, and solid-liquid separation treatment to obtain a rare earth sulfate solution and a neutralized and impurity-removed residue. The above technical solution has the following advantages:

[0211] 1. This invention involves sulfation roasting of mineral-type rare earth ores under a weak oxidizing atmosphere, which can effectively control the form of sulfur oxides in the exhaust gas and achieve efficient separation and resource recovery of fluorine and sulfur in the exhaust gas.

[0212] 2. This invention enables controllable sulfur oxide speciation in the tail gas of the sulfation roasting process, promoting the separation of fluorine and sulfur in the tail gas and their conversion into valuable by-products, while reducing tail gas treatment steps and lowering costs. This invention controls the sulfuric acid roasting process under a weak oxidizing atmosphere, suppressing the generation of SO3 gas and promoting the generation of SO2 gas, thus ensuring that SO3 accounts for a smaller proportion of the total SO2 in the tail gas. x The proportion of SO2 is less than 20%. After water spray absorption, HF / SiF4 gas is converted into fluorinated acid, while SO2 gas is further catalytically oxidized into SO3 and then recycled to produce 98% concentrated sulfuric acid product. At the same time, the tail gas treatment process reduces the steps of pressure filtration and vacuum evaporation, thereby reducing the tail gas treatment cost.

[0213] 3. During the sulfation roasting process in a weakly oxidizing atmosphere, all rare earth elements in mineral-type rare earth ores are converted into easily leached RE2(SO4)3 and RE2O3, among which cerium is completely converted into Ce(SO4). x or CeO x (1.5≤x<2), to avoid the formation of stable phase CeO2, and to improve rare earth leaching rate and rare earth yield.

[0214] Fourth aspect of the invention

[0215] Referring to Figures 1, 8, and 9, a fourth aspect of the present invention provides a method for smelting mineral-type rare earth ores, comprising the following steps:

[0216] Step S1: Pre-treat the mineral-type rare earth ore by mixing the pre-treated mineral-type rare earth ore with concentrated sulfuric acid and then performing sulfation roasting decomposition to obtain sulfuric acid roasted ore and tail gas.

[0217] Step S1 specifically includes:

[0218] Step S1-1: The mineral-type rare earth ore undergoes a first roasting and activation treatment to obtain roasted and activated ore, and a first roasting and activation tail gas is generated.

[0219] Step S1-2: The roasted activated ore is mixed with concentrated sulfuric acid and subjected to sulfation roasting decomposition to obtain the sulfuric acid roasted ore and generate mixed tail gas with low sulfur content.

[0220] Step S2: Leach the sulfuric acid roasted ore with water, weak acid or magnesium-containing solution as leaching agent, and filter to obtain leaching solution and leaching residue;

[0221] Step S3: The leachate is neutralized and purified, and then subjected to solid-liquid separation to obtain rare earth sulfate solution and neutralized residue.

[0222] The preferred method for the first calcination activation is a low-temperature calcination activation temperature of 150℃ to 400℃ and a calcination time of 1h to 3h.

[0223] In the fourth aspect of this invention, the mineral-type rare earth ore has a grade of 45%–70%. It is ball-milled to achieve a median particle size (D50) of 5 μm–50 μm, preferably 10 μm–20 μm. This ensures uniform low-temperature roasting activation and allows for homogeneous mixing with sulfuric acid before subsequent sulfation roasting, preventing stratification and ultimately achieving complete decomposition of the mineral-type rare earth ore. A relatively low temperature is used for roasting and activation of the mineral-type rare earth ore, making it more reactive during the subsequent sulfuric acid roasting process.

[0224] The chemical formula for the low-temperature roasting activation of the above-mentioned mineral-type rare earth ores is: 6REFCO3 + H2O = REF3 + RE2O3 + 3REOF + 2HF↑ + 6CO2↑

[0225] Specifically, mineral-type rare earth minerals include mixed minerals of monazite and bastnaesite, bastnaesite, xenotime, and monazite.

[0226] In the fourth aspect of this invention, roasted activated ore is mixed with sulfuric acid for sulfation roasting and decomposition. It has been found that by appropriately increasing the temperature during the low-temperature roasting and activation process, the roasting temperature and sulfuric acid dosage in the subsequent sulfuric acid roasting process can be reduced, thereby reducing the amount of fluorine-sulfur tail gas generated and the sulfur content in the waste gas, achieving a high rare earth leaching rate. Appropriately extending the roasting time during the roasting period can also achieve the above-mentioned effects.

[0227] The chemical formulas for the sulfation roasting decomposition of the above-mentioned mineral-type rare earth ores are as follows: 2REFCO3 + 3H2SO4 = RE2(SO4)3 + 2HF↑ + 2CO2↑ + 2H2O↑ 2REF3 + 3H2SO4 = RE2(SO4)3 + 3HF↑ 2RE2O3 + 3H2SO4 = RE2(SO4)3 + 3H2O↑ 2REOF + 3H2SO4 = RE2(SO4)3 + 2H2O↑ + 2HF↑ CaF2 + H2SO4 = CaSO4↓ + 2HF↑ SiO2 + 4HF = SiF4↑ + 2H2O↑ H2SO4 = SO3↑ + H2O↑

[0228] Specifically, the concentration of the concentrated sulfuric acid is 85wt% to 98wt%. The total amount of concentrated sulfuric acid used in the sulfation roasting is 1.0 to 2.0 times the mass ratio of acid to ore, preferably 1.2 to 1.5.

[0229] Furthermore, the calcination temperature is 150℃~450℃, and the calcination time is 2h~12h, preferably the calcination temperature is 200℃~300℃, and the calcination time is 3h~5h.

[0230] In a specific implementation of the fourth aspect of the present invention, tail gases are generated in the two stages of steps S1-1 and S1-2. The first stage uses low-temperature roasting activation to activate and decompose the mineral-type rare earth ore, generating hydrofluoric acid gas. The second stage uses sulfation roasting to completely decompose it into water-soluble rare earth sulfate, generating a fluorine-sulfur mixed gas. The present invention separately recovers the different tail gases generated in the two roasting stages. Therefore, in the preferred embodiment of the present invention, a two-stage method is used to treat the tail gases. The hydrofluoric acid gas generated by the first stage low-temperature roasting activation is recycled after being prepared into hydrofluoric acid by water absorption. The low-temperature roasting activation tail gas is specifically a mixed gas of hydrogen fluoride and carbon dioxide, which is used to prepare pure hydrofluoric acid product by water absorption. The fluorine-sulfur tail gas generated by the second stage sulfation roasting tail gas is separated and treated by water absorption to obtain recovered concentrated sulfuric acid and fluorine-containing products. The concentrated sulfuric acid is reused in step S1-2. In the second stage, a four-stage circulating spray is first used to absorb SO3, HF, and SiF4 in the exhaust gas to obtain a mixed acid with a low H2SO4 concentration of about 40%. The mixed acid with a low H2SO4 concentration is first filtered to separate solid impurities, and then evaporated under reduced pressure to obtain sulfuric acid with a high H2SO4 concentration of about 70% aqueous phase and a mixture of HF and SiF4 gas phase. The mixture of HF and SiF4 gas phase is then condensed to obtain 15% mixed fluorine acid. HF and SiF4 are used to prepare fluorine-containing products. The SO2 in the exhaust gas is defluorinated by flue gas, and then absorbed, desorbed, and catalytically oxidized by organic amines to prepare sulfuric acid with a concentration of 98%.

[0231] In step S2, leaching is performed using water, a weak acid, or a magnesium-containing solution; specifically, leaching with water is used. 。

[0232] Step S3: Neutralize and remove impurities from the aqueous leaching solution and perform solid-liquid separation to obtain rare earth sulfate solution and neutralized residue.

[0233] In this invention, to improve the rare earth leaching rate, it is necessary to control the amount of water during the leaching process. Since the solubility of rare earth sulfate solution is below 45 g / L, a high rare earth content is beneficial for improving production efficiency. However, if the rare earth sulfate concentration exceeds 45 g / L, it easily forms rare earth sulfate crystals, affecting the leaching rate. Short leaching times result in incomplete leaching of rare earths, while excessively long leaching times negatively impact production efficiency. Therefore, the sulfuric acid-roasted ore is leached with water at a mass ratio of 1:5 to 1:20 for 3 to 6 hours.

[0234] The fourth aspect of the present invention is further described through the following embodiments, which should not be construed as limiting the present invention.

[0235] Unless otherwise specified, all reagents used in the following examples are commercially available products.

[0236] Two sets of experiments were set up. Comparative Example 1 did not include the low-temperature roasting activation step; bastnaesite and concentrated sulfuric acid were directly mixed and sulfation roasted. Comparative Example 2 included the low-temperature roasting activation step, with a bastnaesite particle size D50 of 60 μm. Comparative Example 3 included the low-temperature roasting activation step, with a roasting temperature of 100℃ and a concentrate to concentrated sulfuric acid mass ratio of 1:0.9. Examples 1-2 of the fourth aspect first underwent a low-temperature roasting activation step, followed by sulfation roasting. The specific experimental steps of Comparative Examples 1-3 and Examples 1 and 2 are as follows:

[0237] Comparative Example 4-1

[0238] (1) Fluorocarbon cerium ore with a particle size distribution D50 of 10 μm was mixed with concentrated sulfuric acid and subjected to sulfation roasting to obtain sulfuric acid roasted ore. The roasting temperature was 350℃ and the roasting time was 3h. The concentration of concentrated sulfuric acid used was 90wt%, and the mass ratio of concentrate to concentrated sulfuric acid was 1:1.3. All rare earth elements in fluorocarbon cerium ore were converted into the easily leached phase RE2(SO4)3.

[0239] (2) The sulfuric acid roasted ore was leached with water at a mass ratio of 1:15. The water leaching solution was neutralized, impurities removed, and solid-liquid separation was performed to obtain sulfuric acid rare earth solution and leaching residue. The rare earth yield was 76%, and the sulfur content in the fluorine and sulfur tail gas was 28%.

[0240] (3) The sulfuric acid roasting tail gas is treated by water absorption and separation to obtain concentrated sulfuric acid and fluorine-containing products, and the obtained concentrated sulfuric acid is recycled for the sulfuric acid roasting process.

[0241] Comparative Example 4-2

[0242] (1) Fluorocarbonate cerium ore with a particle size distribution D50 of 60 μm was roasted at 200℃ for 2 h to obtain activated roasted ore. The activated roasted ore was mixed with concentrated sulfuric acid and roasted to obtain sulfuric acid roasted ore. The roasting temperature was 500℃ and the roasting time was 3 h. The concentration of concentrated sulfuric acid used was 90 wt%, and the mass ratio of concentrate to concentrated sulfuric acid was 1:1.3. All rare earth elements in fluorocarbonate cerium ore were converted into the easily leached phase RE2(SO4)3.

[0243] (2) The sulfuric acid roasted ore was leached with water at a mass ratio of 1:15. The water leaching solution was neutralized, impurities removed, and solid-liquid separation was performed to obtain sulfuric acid rare earth solution and leaching residue. The rare earth yield was 84%.

[0244] (3) The two roasting tail gases are recovered separately. The low-temperature roasting activation tail gas is absorbed by water to obtain hydrofluoric acid and then recycled. The sulfur content in the sulfation roasting tail gas is 21%. It is treated by water absorption and separation to obtain concentrated sulfuric acid and fluorine-containing products.

[0245] Comparative Example 4-3

[0246] (1) Fluorocarbonate cerium ore with a particle size distribution D50 of 20 μm was roasted at 200℃ for 3 h to obtain activated roasted ore. The activated roasted ore was mixed with concentrated sulfuric acid and roasted to obtain sulfuric acid roasted ore. The roasting temperature was 100℃ and the roasting time was 4 h. The concentration of concentrated sulfuric acid used was 90 wt%, and the mass ratio of concentrate to concentrated sulfuric acid was 1:0.9. All rare earth elements in fluorocarbonate cerium ore were converted into the easily leached phase RE2(SO4)3.

[0247] (2) The sulfuric acid roasted ore was leached with water at a mass ratio of 1:15. The water leaching solution was neutralized, impurities removed, and solid-liquid separation was performed to obtain a sulfuric acid rare earth solution and leaching residue. The rare earth yield was 79%.

[0248] (3) The two roasting tail gases are recovered separately. The low-temperature roasting activation tail gas is absorbed by water to obtain hydrofluoric acid and then recycled. The sulfur content in the sulfation roasting tail gas is 3.1%. It is treated by water absorption and separation to obtain concentrated sulfuric acid and fluorine-containing products.

[0249] Example 4-1

[0250] The process for treating bastnaesite described in this embodiment, following the sulfuric acid roasting flow chart shown in Figure 2, includes the following steps:

[0251] (1) Fluorocarbon cerium ore with a particle size distribution D50 of 10 μm was roasted at 300℃ for 2 h to obtain activated roasted ore. The activated roasted ore was mixed with concentrated sulfuric acid and then sulfatated to obtain sulfuric acid roasted ore. The roasting temperature was 250℃ and the roasting time was 4 h. The concentration of concentrated sulfuric acid used was 90 wt%. The mass ratio of concentrate to concentrated sulfuric acid was 1:1.3. All rare earth elements in fluorocarbon cerium ore were converted into the easily leached phase RE2(SO4)3.

[0252] (2) The sulfuric acid roasted ore was leached with water at a mass ratio of 1:15. The water leaching solution was neutralized, impurities removed, and solid-liquid separation was performed to obtain a sulfuric acid rare earth solution and leaching residue. The rare earth yield was 97%.

[0253] (3) The two roasting tail gases are recovered separately. The low-temperature roasting activation tail gas is absorbed by water to obtain hydrofluoric acid and then recycled. The sulfur content in the sulfation roasting tail gas is 5.4%. It is treated by water absorption and separation to obtain recovered concentrated sulfuric acid and fluorine-containing products.

[0254] Example 4-2

[0255] (1) Fluorocarbonate cerium ore with a particle size distribution D50 of 20 μm was roasted at 350℃ for 1 h to obtain activated roasted ore. The activated roasted ore was mixed with concentrated sulfuric acid and subjected to sulfation roasting to obtain sulfuric acid roasted ore. The roasting temperature was 200℃ and the roasting time was 3 h. The concentration of concentrated sulfuric acid used was 90 wt%, and the mass ratio of concentrate to concentrated sulfuric acid was 1:1.3. All rare earth elements in fluorocarbonate cerium ore were converted into the easily leached phase RE2(SO4)3.

[0256] (2) The sulfuric acid roasted ore was leached with water at a mass ratio of 1:15. The water leaching solution was neutralized, impurities removed, and solid-liquid separation was performed to obtain sulfuric acid rare earth solution and leaching residue. The rare earth yield was 94%.

[0257] (3) The two roasting tail gases are recovered separately. The low-temperature roasting activation tail gas is absorbed by water to obtain hydrofluoric acid and then recycled. The sulfur content in the sulfation roasting tail gas is 5%, and it is treated by water absorption and separation to obtain recovered concentrated sulfuric acid and fluorine-containing products.

[0258] The steps of Examples 4-46 in the fourth aspect are the same as those in Examples 4-1 and 4-2, and the conditions for each step are shown in Table 5 below. The final rare earth yield is shown in Table 5 below.

[0259] Table 5: Experimental conditions and corresponding total rare earth yields of Examples 4-46 in the fourth aspect

[0260] Therefore, the fourth aspect of this invention utilizes low-temperature activation roasting to decompose fluorocarbon cerium ore, followed by concentrated sulfuric acid roasting and decomposition, water leaching for neutralization and impurity removal, ultimately yielding a rare earth sulfate leaching solution and leaching residue. This significantly improves the rare earth yield. The hydrogen fluoride gas generated during the activation roasting process is absorbed by water, and the sulfur content in the mixed gas generated by sulfuric acid roasting is less than 8%. Water absorption and separation are then used to recover concentrated sulfuric acid and fluorine-containing products. This invention effectively reduces roasting temperature and increases the utilization rate of concentrated sulfuric acid, thereby reducing energy and acid consumption, decreasing the amount of mixed waste gas generated, especially its sulfur content, reducing subsequent tail gas treatment inputs, and increasing rare earth leaching rates. This has significant practical implications for low-energy, low-cost, clean, and environmentally friendly treatment of fluorocarbon cerium ore.

[0261] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for smelting mineral-type rare earth ores, characterized in that, Includes the following steps: S1: Pre-treating mineral-type rare earth ore by sulfation roasting decomposition to obtain sulfuric acid roasted ore and tail gas, wherein the pre-treatment includes: Mix the mineral-type rare earth ore, phosphate, and concentrated sulfuric acid; or The mineral-type rare earth ore is mechanically activated, and the mechanically activated mineral-type rare earth ore is mixed with concentrated sulfuric acid; or The mineral-type rare earth ore is mechanically activated, and the mechanically activated mineral-type rare earth ore, phosphate, and concentrated sulfuric acid are mixed together. S2: The sulfuric acid roasted ore is leached with water, a weak acid, or a magnesium-containing solution as the leaching agent, and the leaching solution and leaching residue are obtained by filtration. S3: The leachate is subjected to neutralization and impurity removal, and solid-liquid separation treatment to obtain rare earth sulfate solution and neutralization and impurity removal residue.

2. The smelting method for mineral-type rare earth ore according to claim 1, characterized in that, Step S1, which involves mixing the mineral-type rare earth ore or mechanically activated mineral-type rare earth ore, phosphate, and concentrated sulfuric acid, includes adding phosphate to the mineral-type rare earth ore or mechanically activated mineral-type rare earth ore at a mass ratio of total iron and thorium to total phosphorus of 3 to 5.

3. The smelting method for mineral-type rare earth ores according to claim 2, characterized in that, The phosphates include: apatite and / or monazite.

4. The smelting method for mineral-type rare earth ores according to claim 1, characterized in that, In step S2, the magnesium-containing leaching agent in the sulfuric acid roasted ore leaching process includes magnesium bicarbonate solution, and the mass ratio of sulfuric acid roasted ore to leaching agent is 1:5 to 1:

20.

5. The smelting method for mineral-type rare earth ore according to claim 1, characterized in that, In step S3, an alkaline substance is added to the leachate for neutralization and impurity removal. The alkaline substance includes magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium bicarbonate.

6. The smelting method for mineral-type rare earth ores according to any one of claims 1-5, characterized in that, The rare earth sulfate solution is extracted, transformed, and separated using P507 and / or P204 saponified with magnesium bicarbonate solution to obtain a single rare earth chloride solution and a magnesium-containing solution. The magnesium-containing solution includes magnesium sulfate wastewater, which is treated and recycled for leaching or used to prepare magnesium bicarbonate solution.

7. The smelting method for mineral-type rare earth ores according to claim 1, characterized in that, The mechanical activation in step S1 includes microwave treatment with a frequency of 2000MHz to 3000MHz. After mechanical activation, the particle size is D90 < 50μm and D50 < 18μm.

8. The smelting method for mineral-type rare earth ores according to claim 6, characterized in that, The preparation process of the magnesium bicarbonate solution includes the following steps: Step A: The pH of the magnesium sulfate wastewater generated from rare earth extraction and separation is adjusted to 10.0-12.5 using a calcium-containing alkaline substance to obtain a slurry containing magnesium hydroxide and calcium sulfate. Step B involves carbonizing the slurry containing magnesium hydroxide and calcium sulfate using CO2, followed by solid-liquid separation to obtain a magnesium bicarbonate solution and a calcium sulfate byproduct.

9. The smelting method for mineral-type rare earth ores according to claim 8, characterized in that, The concentration of the magnesium bicarbonate solution, calculated as MgO, is 5–15 g / L.

10. The smelting method for mineral-type rare earth ore according to claim 1, characterized in that, In step S1, the sulfation roasting decomposition includes performing the sulfation roasting decomposition under a weak oxidizing atmosphere to obtain the sulfuric acid roasted ore and the tail gas.

11. The smelting method for mineral-type rare earth ore according to claim 10, characterized in that, The weak oxidizing atmosphere includes: a reducing gas and / or an inert gas; the oxygen content of the weak oxidizing atmosphere is 0.1% to 15%, preferably 5% to 10%; or, the weak oxidizing atmosphere includes air, and at least one of the exhaust gas, N2, CO2 and CO.

12. The smelting method for mineral-type rare earth ore according to claim 10, characterized in that, The sulfation roasting decomposition temperature is 200℃~450℃, preferably 250℃~350℃; the roasting time is 2h~12h, preferably 3h~5h.

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