CN117626012B - Hydrochloric acid treatment process for mixed rare earth concentrate - Google Patents

Abstract

The invention provides a hydrochloric acid treatment process of mixed rare earth concentrate, and belongs to the technical field of rare earth metallurgy. The invention mixes, calcines and grinds the mixed rare earth concentrate and the calcium-containing compound to obtain finely ground mineral, leaches the finely ground mineral by dilute hydrochloric acid to obtain phosphoric acid and hydrogen fluoride, and leaches the leached filter residue by hydrochloric acid to obtain rare earth chloride. The invention adopts four steps of high Wen Gaihua roasting-fine grinding dissociation of roasting ore-dilute hydrochloric acid phosphoric acid leaching-rare earth leaching by hydrochloric acid, and can obtain phosphoric acid, rare earth chloride and high-purity hydrofluoric acid. In addition, compared with the prior art, the method has the advantages of shorter process flow, saving the transformation of sulfuric acid leaching and hydrochloric acid, and remarkably reducing the three wastes. In addition, the hydrogen fluoride gas prepared by the method has no other impurity elements, the obtained rare earth chloride has fewer impurities, the subsequent treatment is more convenient, and compared with the prior sulfuric acid roasting process, the hydrogen fluoride gas has fewer impurities and is easy to treat.

Description

A hydrochloric acid treatment process for mixed rare earth concentrate

Technical Field

The invention belongs to the technical field of rare earth metallurgy, and in particular relates to a hydrochloric acid treatment process for mixed rare earth concentrate.

Background Art

The traditional smelting process of mixed rare earth concentrate is mainly sulfuric acid roasting and caustic soda method. Sulfuric acid roasting is divided into two processes: low-temperature concentrated sulfuric acid roasting and high-temperature concentrated sulfuric acid roasting. The sulfuric acid roasting process has problems such as long process, many types of raw materials and large amount of raw materials, high cost, large amount of "three wastes" and high difficulty in treatment, and a large amount of phosphorus in the concentrate entering the rare earth mixed solution is difficult to effectively separate and recover, resulting in a waste of phosphorus and fluorine resources. The caustic soda process includes rare earth concentrate-decalcification treatment-caustic soda decomposition-filtration and washing-hydrochloric acid dissolution-mixed rare earth chloride-multi-stage extraction and other steps. This process has high requirements for the grade of rare earth concentrate, long process flow, large amount of washing water, and a large amount of sodium fluoride and sodium phosphate entering the washing solution is difficult to handle.

CN109837385A discloses a method for heating, melting, converting and decomposing rare earth ores, wherein carbon materials are added to the furnace, and the heating function of carbonic acid materials and arc heating are used to melt the rare earth ores of endosperm phosphorus-removing and fluorine-fixing materials, wherein the fluorine-fixing material is calcium carbonate. However, the fluorine-containing substances generated by this process are not conducive to recycling, the fluorine removal rate still needs to be improved, and hydrosilicic acid cannot be obtained.

CN114480835A discloses a decomposition method and application of a mixed rare earth concentrate, wherein the mixed rare earth concentrate, magnesium chloride and carbon powder are roasted and decomposed under the action of microwaves to obtain roasted ore; the roasted ore is leached with a first inorganic acid to obtain acid leaching residue and a first rare earth solution; the acid leaching residue is separated to obtain magnesium fluoride and undecomposed rare earth concentrate respectively; the undecomposed rare earth concentrate is alkali-decomposed to obtain alkaline wastewater and alkaline hydrolysis ore; the alkaline wastewater is cooled, concentrated and crystallized to obtain sodium phosphate and recovered alkaline solution; the alkaline hydrolysis ore is leached with a second inorganic acid to obtain a second rare earth solution. This decomposition method cannot obtain hydrofluoric acid, but magnesium fluoride is obtained, not fluoroapatite, and the fluorine removal rate still needs to be improved.

CN109536746A discloses a method for circulating pulping and decomposition of low-calcium high-grade mixed rare earth concentrate, comprising the following steps: mixing low-calcium high-grade mixed rare earth concentrate with sulfuric acid solution in proportion, carrying out pulping reaction under heating state, reacting and decomposing fluorine-containing minerals, and forming fluorine-containing mixed acid byproducts after tail gas absorption; after the reaction, solid-liquid separation to obtain acid leaching liquid and acid leaching residue, the acid leaching residue is subjected to water leaching to obtain water leaching residue and water leaching liquid, the water leaching liquid is neutralized to form phosphorus iron thorium slag and rare earth sulfate solution; the water leaching residue and phosphorus iron thorium slag are mixed with sodium hydroxide solution, pulped and decomposed; after treatment, trisodium phosphate byproducts and rare earth chloride solution are obtained. The fluorine removal rate and phosphorus recovery rate of this method still need to be improved, and the process has high requirements on the grade of mixed rare earth concentrate, generates more wastewater, and cannot obtain a relatively simple hydrofluoric acid.

To this end, the present invention proposes a hydrochloric acid treatment process for mixed rare earth concentrate.

Summary of the invention

In order to solve the above technical problems, the present invention proposes a hydrochloric acid treatment process for mixed rare earth concentrate. The treatment process of the present invention can recover hydrofluoric acid, phosphoric acid and rare earth chloride, which significantly shortens the process and reduces the amount of industrial waste.

To achieve the above object, the present invention provides a hydrochloric acid treatment process for a mixed rare earth concentrate, comprising the following steps:

A mixed rare earth concentrate is mixed with a calcium-containing compound, roasted, and then ground to obtain a finely ground mineral. The finely ground mineral is leached with hydrochloric acid of a first concentration, fluoroapatite is leached, phosphorus is converted into phosphoric acid and enters the leaching solution, and fluorine is converted into hydrogen fluoride gas and overflows. The leaching solution and the filter residue are separated by filtration, phosphorus is extracted from the leaching solution, and undecomposed rare earth oxide enters the filter residue. The leaching is then leached with hydrochloric acid of a second concentration to obtain rare earth chloride; the second concentration is greater than the first concentration.

Furthermore, the mixed rare earth concentrate is monazite and bastnaesite.

Furthermore, the calcium-containing compound is CaO and/or CaCO _3. If the calcium-containing compound is not added, the rare earth in the rare earth concentrate will generate rare earth fluoride and a small amount of rare earth oxide, and most of the monazite cannot be decomposed. The rare earth fluoride and monazite cannot be decomposed during subsequent leaching with hydrochloric acid, resulting in very low recovery rates of phosphorus and rare earth and very low removal rates of fluorine.

Furthermore, the particle size of the mixed rare earth concentrate is less than or equal to 200 mesh, and the particle size of the calcium-containing compound is less than or equal to 200 mesh.

Furthermore, the mass ratio of the mixed rare earth concentrate to the calcium-containing compound (calculated as CaO) is 100:(15-20), preferably, the mass ratio is 100:(17-20). When the calcium-containing compound is excessive, it will lead to the presence of excessive free calcium oxide, which will increase the amount of hydrochloric acid consumed during phosphorus and fluorine removal, reduce the acidity of the solution, and be unfavorable for the leaching of fluorapatite, thereby causing a decrease in the phosphorus leaching rate and the fluorine removal rate.

Furthermore, the temperature of mixed rare earth concentrate and calcium-containing compound mixed roasting is 950-1100°C, and the time is 1.5-3h. Preferably, the temperature of mixed rare earth concentrate and calcium-containing compound mixed roasting is 970-1050°C, and the time is 2-2.5h. The fluorocarbon cerium and monazite in the mixed rare earth concentrate that are difficult to leach with hydrochloric acid are converted into easy-to-handle rare earth oxide. When the roasting temperature is low, the rare earth fluoride produced by the decomposition of fluorocarbon cerium ore in the mixed rare earth concentrate cannot react with calcium oxide, and the monazite in the ore does not react completely with calcium oxide, resulting in low leaching rates of rare earth and phosphorus and low removal rates of fluorine; when the roasting temperature is high, it is easy to burn the newly produced rare earth oxide, reduce its activity, and make it difficult to be leached.

Furthermore, the mixed rare earth concentrate is mixed with the calcium-containing compound and then roasted and ground to less than 300 meshes to ensure effective dissociation of rare earth oxide and fluoroapatite. When the mineral particle size is coarse after roasting, the phosphorus and fluorine leaching effect is poor. This is because the reaction product rare earth oxide generated during roasting is wrapped with fluoroapatite. During the phosphorus and fluorine removal reaction, the fluoroapatite wrapped in the rare earth oxide is difficult to contact with hydrochloric acid, resulting in incomplete reaction, which reduces the removal rate of phosphorus and fluorine.

Further, the concentration of the first concentration of hydrochloric acid is 1-2 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1:(2-4), and the leaching is performed for 15-30 min at room temperature. Preferably, the concentration of the first concentration of hydrochloric acid is 1.5-2 mol/L, and the leaching is performed for 25-30 min at room temperature. When the concentration of hydrochloric acid for removing phosphorus and rare earth is low, it is not conducive to the removal of phosphorus and fluorine, and the fluoroapatite reaction is not complete, which reduces the phosphorus leaching rate and the fluorine removal rate, resulting in a large amount of phosphorus still existing in the solution during the subsequent rare earth leaching; when the concentration of hydrochloric acid for removing phosphorus and fluorine is high, the fluoroapatite reaction is more complete, but it also leads to the leaching of rare earth oxide, resulting in an increase in the loss rate of rare earth, resulting in a decrease in the yield of rare earth elements during the subsequent rare earth leaching.

Furthermore, the concentration of the second concentration of hydrochloric acid is 4-7 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1:(3-6), leaching is performed at 60-85°C for 1.5-3h, preferably, the concentration of hydrochloric acid is 5-6 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1:(4-5), the leaching time is 2-2.5h, and the leaching temperature is 75-80°C. When the concentration of hydrochloric acid is low, the leaching rate of rare earth oxide is low, and when the concentration of hydrochloric acid is too high, the volatility is large; when the leaching time is short, the rare earth leaching is not thorough, and when the leaching time is long, the smelting efficiency is low; when the leaching temperature is too low, it is not conducive to the overflow of fluorine-containing gas, and when the temperature is too high, the hydrochloric acid volatilizes seriously.

More specifically, a hydrochloric acid treatment process of a mixed rare earth concentrate of the present invention comprises the following steps:

(1) grinding a mixed rare earth concentrate and a calcium-containing compound to a particle size of less than 200 meshes, mixing the mixed rare earth concentrate and the calcium-containing compound, and roasting at 950-1100° C. for 1.5-3 hours to convert bastenasite and monazite in the mixed rare earth concentrate, which are difficult to leach with hydrochloric acid, into easy-to-treat rare earth oxides, wherein the mass ratio of the mixed rare earth concentrate to the calcium-containing compound (calculated as CaO) is 100:(15-20);

(2) mixing the mixed rare earth concentrate and the calcium-containing compound and then grinding them to less than 300 meshes to ensure effective dissociation of the rare earth oxide and the fluoroapatite;

(3) the ground mineral is leached with 1-2 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:(2-4) and a stirring rate of 200-300 r/min at room temperature for 15-30 min to decompose the fluoroapatite, and phosphorus is leached into the leachate to form phosphoric acid. After the leaching is completed, the leachate is filtered to extract and recover phosphorus, and fluorine is generated as hydrogen fluoride gas. The hydrogen fluoride gas is condensed to obtain hydrofluoric acid, thereby realizing the recovery of phosphorus and fluorine;

(4) filtering and separating the filter residue after leaching, wherein the undecomposed rare earth oxide enters the filter residue, and leaching the filter residue with 4-7 mol/L hydrochloric acid at a solid-liquid ratio of 1:(3-6), a stirring rate of 200-300 r/min, and 60-85° C. for 1.5-3 h, and separating the solid and liquid to obtain a rare earth chloride leaching solution.

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

The present invention adopts a four-step process of high-temperature calcination roasting-roasted ore fine grinding and dissociation-dilute hydrochloric acid leaching phosphorus-hydrochloric acid leaching rare earth, which effectively separates phosphorus, fluorine and rare earth in mixed rare earth ore, significantly shortens the smelting process, eliminates sulfuric acid leaching and hydrochloric acid transformation, and greatly reduces the amount of "three wastes". In addition, the hydrogen fluoride gas prepared by the present invention does not have other impurity elements, the obtained rare earth chloride impurities are relatively small, and the subsequent processing is relatively convenient. Compared with the original sulfuric acid roasting process, the gas and liquid components have fewer impurities and are easy to handle.

DETAILED DESCRIPTION

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

It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

The embodiment of the present invention provides a hydrochloric acid treatment process for a mixed rare earth concentrate, comprising the following steps:

The mixed rare earth concentrate and the calcium-containing compound are mixed, roasted and ground to obtain finely ground minerals, and the finely ground minerals are leached with hydrochloric acid of a first concentration, whereby fluoroapatite is decomposed and leached, phosphorus is converted into phosphoric acid, phosphorus is extracted and recovered, and fluorine is converted into hydrogen fluoride gas, and the residue after leaching is filtered and separated, and undecomposed rare earth oxide enters the residue, which is then leached with hydrochloric acid of a second concentration to obtain rare earth chloride; the second concentration of the hydrochloric acid is greater than the first concentration.

In some embodiments of the present invention, the mixed rare earth concentrate is monazite and bastnasite.

In some embodiments of the present invention, the calcium-containing compound is CaO and/or CaCO _3. If the calcium-containing compound is not added, the rare earth in the rare earth concentrate will generate rare earth fluoride and a small amount of rare earth oxide, and most of the monazite cannot be decomposed. The rare earth fluoride and monazite cannot be decomposed during subsequent leaching with hydrochloric acid, resulting in very low recovery rates of phosphorus and rare earth and very low removal rates of fluorine.

In some embodiments of the present invention, the particle size of the mixed rare earth concentrate is less than or equal to 200 mesh, and the particle size of the calcium-containing compound is less than or equal to 200 mesh.

In some embodiments of the present invention, the mass ratio of the mixed rare earth concentrate to the calcium-containing compound (calculated as CaO) is 100:(15-20), preferably, the mass ratio is 100:(17-20). When the calcium-containing compound is excessive, it will lead to the presence of excessive free calcium oxide, which will increase the amount of hydrochloric acid consumed during phosphorus and fluorine removal, reduce the acidity of the solution, and be unfavorable for the leaching of fluorapatite, thereby causing a decrease in the leaching rate of phosphorus and the removal rate of fluorine.

In some embodiments of the present invention, the temperature of mixed rare earth concentrate and calcium-containing compound mixed roasting is 950-1100°C, and the time is 1.5-3h. Preferably, the temperature of mixed rare earth concentrate and calcium-containing compound mixed roasting is 970-1050°C, and the time is 2-2.5h. The fluorocarbon cerium and monazite in the mixed rare earth concentrate that are difficult to leach with hydrochloric acid are converted into easy-to-handle rare earth oxide. When the roasting temperature is low, the rare earth fluoride produced by the decomposition of fluorocarbon cerium ore in the mixed rare earth concentrate cannot react with calcium oxide, and the monazite in the ore does not react completely with calcium oxide, resulting in low leaching rates of rare earth and phosphorus and low removal rates of fluorine; when the roasting temperature is high, it is easy to burn the newly produced rare earth oxide, reduce its activity, and make it difficult to be leached.

In some embodiments of the present invention, the mixed rare earth concentrate is mixed with the calcium-containing compound and then ground to less than 300 meshes after roasting to ensure effective dissociation of rare earth oxide and fluoroapatite. When the mineral particle size is coarse after roasting, the phosphorus and fluorine leaching effect is poor, because the reaction product rare earth oxide generated during roasting and fluoroapatite are mutually wrapped, and the fluoroapatite wrapped in the rare earth oxide is difficult to contact with hydrochloric acid during the phosphorus and fluorine removal reaction, resulting in incomplete reaction, which reduces the removal rate of phosphorus and fluorine.

In some embodiments of the present invention, the concentration of the first concentration of hydrochloric acid is 1-2 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1: (2-4), and the leaching is carried out for 15-30 min at room temperature. Preferably, the concentration of the first concentration of hydrochloric acid is 1.5-2 mol/L, and the leaching is carried out for 25-30 min at room temperature. When the concentration of hydrochloric acid for removing phosphorus and rare earth is low, it is not conducive to the removal of phosphorus and fluorine, and the reaction of fluoroapatite is not complete, which reduces the phosphorus leaching rate and fluorine removal rate, resulting in a large amount of phosphorus still existing in the solution during the subsequent rare earth leaching; when the concentration of hydrochloric acid for removing phosphorus and fluorine is high, the reaction of fluoroapatite is more complete, but it also leads to the leaching of rare earth oxide, resulting in an increase in the loss rate of rare earth, resulting in a decrease in the yield of rare earth elements during the subsequent rare earth leaching.

In some embodiments of the present invention, the concentration of the second concentration of hydrochloric acid is 4-7 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1: (3-6), and the leaching is performed at 60-85°C for 1.5-3h. Preferably, the concentration of hydrochloric acid is 5-6 mol/L, the solid-liquid ratio of hydrochloric acid leaching is 1: (4-5), the leaching temperature is 75-80°C, and the leaching time is 2-2.5h. When the concentration of hydrochloric acid is low, the leaching rate of rare earth oxide is low, and when the concentration of hydrochloric acid is too high, the volatility is large; when the leaching time is short, the rare earth leaching is not thorough, and when the leaching time is long, the smelting efficiency is low; when the leaching temperature is too low, it is not conducive to the overflow of fluorine-containing gas, and when the temperature is too high, the hydrochloric acid volatilizes seriously.

The room temperature in the embodiments of the present invention refers to "25±5°C".

The technical solution of the present invention is further illustrated by the following embodiments.

Example 1

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 56.05%, ΣFe 3.70%, F 7.50%, P 3.50%, CaO 5.55%, BaO 4.70%, S 1.86%, ThO ₂ 1.86%, Nb ₂ O ₅ 0.05%, and the balance is other components; grind CaO to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaO, placing them in a reaction furnace, and roasting them at 970°C for 2 hours, wherein the mass ratio of the mixed rare earth concentrate to CaO is 100:17;

(2) Mixing rare earth concentrate and CaO, roasting and grinding to less than 300 mesh, leaching the finely ground minerals with 1.5 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:4, a stirring rate of 200 r/min, and room temperature for 25 minutes, filtering and collecting the leachate after leaching, fluoroapatite is leached into the leachate, phosphorus is converted into phosphoric acid, and the leachate is filtered and then extracted to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby realizing the recovery of phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 5 mol/L hydrochloric acid at a solid-liquid ratio of 1:5, a stirring rate of 200 r/min, and 80°C for 2 h. The solid-liquid separation is performed to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Example 2

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 56.05%, ΣFe: 3.70%, F 7.50%, P 3.50%, CaO5.55%, BaO 4.70%, S1.86%, ThO ₂ 1.86%, Nb ₂ O ₅ 0.05%, and the balance is other components; grind CaCO ₃ to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaCO ₃ in a reactor, and roasting at 1000°C for 2.5 hours, wherein the mass ratio of the mixed rare earth concentrate to CaCO ₃ is 100:35.7 (calculated as CaO, the mass ratio is 100:20);

(2) Mixing rare earth concentrate and _CaCO3, roasting and grinding to less than 300 mesh, leaching the finely ground minerals with 1.5 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:4, a stirring rate of 200 r/min, and room temperature for 30 min, filtering and collecting the leachate after leaching, fluoroapatite is leached into the leachate, phosphorus is converted into phosphoric acid, and the leachate is filtered and then extracted to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby realizing the recovery of phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 6 mol/L hydrochloric acid at a solid-liquid ratio of 1:6, a stirring rate of 200 r/min, and 75°C for 2.5 h. The solid-liquid separation is performed to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Example 3

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 60.10%, ΣFe 3.20% (total iron), F 7.80%, P 3.50%, CaO4.35%, BaO 3.71%, S1.26%, ThO ₂ 1.23%, Nb ₂ O ₅ 0.06%, and the balance is other components; Grind CaCO ₃ to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaCO ₃ in a reactor, and roasting at 1100°C for 2 hours, wherein the mass ratio of the mixed rare earth concentrate to CaCO ₃ is 100:26.8 (calculated as CaO, the mass ratio is 100:15);

(2) Mixing a mixed rare earth concentrate and a calcium-containing compound, roasting and grinding the mixture to a size of less than 300 mesh, subjecting the ground minerals to leaching with 2 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:2, a stirring rate of 200 r/min, and room temperature for 30 min, filtering and collecting the leachate after the leaching, fluoroapatite is leached, phosphorus is converted into phosphoric acid, filtering and extracting the leachate to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby recovering phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 5 mol/L hydrochloric acid at a solid-liquid ratio of 1:5, a stirring rate of 250 r/min, and 80°C for 2 h. The solid-liquid separation is performed to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Example 4

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 65.10%, ΣFe 3.20%, F 7.80%, P 4.10%, CaO4.35%, BaO 2.15%, S1.36%, ThO ₂ 1.03%, Nb ₂ O ₅ 0.06%, and the balance is other components; grind CaO to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaO, placing them in a reaction furnace, and roasting them at 1000°C for 2 hours, wherein the mass ratio of the mixed rare earth concentrate to CaO is 100:20;

(2) Mixing a mixed rare earth concentrate and a calcium-containing compound, roasting and grinding the mixture to a size of less than 300 mesh, leaching the finely ground minerals with 1.5 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:3, a stirring rate of 250 r/min, and room temperature for 20 min, filtering and collecting the leachate after leaching, fluoroapatite is leached, phosphorus is converted into phosphoric acid, and the leachate is filtered and extracted to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby recovering phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 6 mol/L hydrochloric acid at a solid-liquid ratio of 1:4, a stirring rate of 250 r/min, and 80°C for 2.5 h. The solid-liquid separation is performed to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Example 5

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 65.10%, ΣFe 3.20%, F 7.80%, P 4.10%, CaO4.35%, BaO 2.15%, S1.36%, ThO ₂ 1.03%, Nb ₂ O ₅ 0.06%, and the balance is other components; grind CaO to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaO, placing them in a reaction furnace, and roasting them at 950°C for 3 hours, wherein the mass ratio of the mixed rare earth concentrate to CaO is 100:20;

(2) Mixing a mixed rare earth concentrate and a calcium-containing compound, roasting and grinding the mixture to a size of less than 300 mesh, subjecting the ground minerals to leaching with 2 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:2, a stirring rate of 250 r/min, and room temperature for 15 min, filtering and collecting the leachate after the leaching, fluoroapatite is leached, phosphorus is converted into phosphoric acid, and the leachate is filtered and extracted to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby recovering phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 4 mol/L hydrochloric acid at a solid-liquid ratio of 1:6, a stirring rate of 300 r/min, and 85°C for 1.5 h. The solid-liquid is separated to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Example 6

(1) Grind the mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) to a particle size of less than 200 meshes. The chemical composition according to mass percentage is as follows: REO 65.10%, ΣFe 3.20%, F 7.80%, P 4.10%, CaO4.35%, BaO 2.15%, S1.36%, ThO ₂ 1.03%, Nb ₂ O ₅ 0.06%, and the balance is other components; grind CaO to a particle size of less than 200 meshes;

Mixing the mixed rare earth concentrate and CaO, placing them in a reaction furnace, and roasting them at 1100°C for 1.5 hours, wherein the mass ratio of the mixed rare earth concentrate to CaO is 100:15;

(2) Mixing a mixed rare earth concentrate and a calcium-containing compound, roasting and grinding the mixture to a size of less than 300 mesh, leaching the finely ground minerals with 1 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:4, a stirring rate of 250 r/min, and room temperature for 30 min, filtering and collecting the leachate after leaching, fluoroapatite is leached, phosphorus is converted into phosphoric acid, and the leachate is filtered and extracted to recover phosphorus, and fluorine is converted into hydrogen fluoride gas, which is condensed to obtain hydrofluoric acid, thereby recovering phosphorus and fluorine;

(3) Filter and separate the residue after leaching. The undecomposed rare earth oxide enters the residue. The residue is leached with 7 mol/L hydrochloric acid at a solid-liquid ratio of 1:3, a stirring rate of 250 r/min, and 60° C. for 3 h. The solid-liquid separation is performed to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Comparative Example 1

The same as Example 1, except that CaO is not added, specifically:

(1) The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes. The chemical composition according to mass percentage was tested as follows: REO 56.05%, ΣFe 3.70%, F 7.50%, P 3.50%, CaO 5.55%, BaO 4.70%, S 1.86%, ThO ₂ 1.86%, Nb ₂ O ₅ 0.05%, and the balance was other components;

(2) placing the mixed rare earth concentrate in a reaction furnace, roasting at 970° C. for 2 h, and then grinding it to less than 300 meshes, leaching the finely ground minerals with 1.5 mol/L dilute hydrochloric acid at a solid-liquid ratio of 1:4, a stirring rate of 200 r/min, and room temperature for 25 min, filtering and collecting the leachate after leaching, fluoroapatite is leached into the leachate, and phosphorus is extracted and recovered, phosphorus is converted into phosphoric acid, fluorine is converted into hydrogen fluoride gas, and the hydrogen fluoride gas is condensed to obtain hydrofluoric acid, thereby realizing the recovery of phosphorus and fluorine;

(3) The filter residue is leached with 5 mol/L hydrochloric acid at a solid-liquid ratio of 1:5, a stirring rate of 200 r/min, and 80° C. for 2 h, and the solid-liquid is separated to obtain a rare earth chloride leaching solution, which can be used for rare earth extraction.

Comparative Example 2

Same as Example 1, except that the mass ratio of the mixed rare earth concentrate to CaO is 100:30.

Comparative Example 3

The same as Example 1, except that the mixed rare earth concentrate is mixed with CaO and placed in a reaction furnace, and roasted at 750° C. for 2 h.

Comparative Example 4

The same as Example 1, except that the mixed rare earth concentrate is mixed with CaO and placed in a reaction furnace, and roasted at 1200° C. for 2 h.

Comparative Example 5

The same as Example 1, except that the finely ground mineral after grinding is leached using 0.5 mol/L dilute hydrochloric acid.

Comparative Example 6

The same as Example 1, except that the finely ground mineral after grinding is leached using 4 mol/L dilute hydrochloric acid.

Comparative Example 7

The same as Example 1, except that the mixed rare earth concentrate is mixed with CaO and then roasted and ground to less than 100 mesh.

Performance Testing

The phosphorus recovery rate, fluorine overflow rate and rare earth (REO) recovery rate in the treatment processes of Examples 1-6 and Comparative Examples 1-7 were measured, and the measurement method was as follows:

Determination of fluorine content: using fluorine evaporation method;

Determination of phosphorus content: ICP method;

Determination of REO content: plasma method, volumetric method;

The phosphorus recovery rate, fluorine overflow rate and rare earth (REO) recovery rate (i.e., yield) are calculated according to formulas (1)-(3):

In the formula: W _RE0 is the rare earth (REO) content in the mixed rare earth concentrate, wt%; _m0 is the mass of the mixed rare earth concentrate, g; W _RE2 is the rare earth content in the filter residue of step (4), wt%; _m2 is the mass of the filter residue in step (4), g; W _P0 is the phosphorus content in the mixed rare earth concentrate, wt%; W _P1 is the phosphorus content in the filter residue after phosphorus leaching in dilute hydrochloric acid, wt%; _m1 is the mass of the residue after phosphorus leaching in dilute hydrochloric acid, g; W _F0 is the fluorine content in the mixed rare earth concentrate, wt%; W _F1 is the fluorine content in the filter residue after phosphorus leaching in dilute hydrochloric acid, wt%.

The measurement results of phosphorus recovery rate, fluorine overflow rate and rare earth recovery rate in the treatment processes of Examples 1-6 and Comparative Examples 1-7 are shown in Table 1.

Table 1 Determination results of phosphorus recovery rate, fluorine overflow rate and rare earth recovery rate

It can be seen from Table 1 that the treatment process of the embodiment of the present invention can obtain phosphoric acid, rare earth chloride and hydrofluoric acid, and the recovery rates of rare earth chloride and phosphoric acid and the removal rate of hydrofluoric acid are better than those of the comparative example.

By comparing Example 1 with Comparative Example 1, it can be seen that when calcium oxide particles are not added, the rare earth in the rare earth concentrate generates rare earth fluoride and a small amount of rare earth oxide, and most of the monazite is not decomposed. The rare earth fluoride and monazite cannot be decomposed when leached with hydrochloric acid, so the recovery rate of phosphorus and rare earth and the removal rate of fluorine are very low.

By comparing Example 1 with Comparative Example 2, it can be seen that when the CaO particles are in excess, there is excess free calcium oxide, which increases the amount of hydrochloric acid consumed during phosphorus and fluoride removal, reduces the acidity of the solution, and is not conducive to the leaching of fluorapatite, thereby resulting in a decrease in the phosphorus leaching rate and the fluorine removal rate.

Compared with Example 3, when the roasting temperature is low, the rare earth fluoride produced by the decomposition of bastnaesite cannot react with calcium oxide, and the reaction of monazite in the ore with calcium oxide is not complete, resulting in low leaching rates of rare earth and phosphorus and low removal rates of fluorine.

Compared with Example 4, when the calcination temperature is high, the newly produced rare earth oxide is easily burned to death, reducing its activity, making it difficult to be leached.

Compared with Example 5, when the hydrochloric acid concentration for removing phosphorus and rare earth is low, it is not conducive to the removal of phosphorus and fluorine, the fluoroapatite reaction is not complete, the phosphorus leaching rate and the fluorine removal rate are reduced, and a large amount of phosphorus is still present in the solution during the subsequent rare earth leaching.

Compared with Example 6, when the concentration of hydrochloric acid for removing phosphorus and rare earth is high, the fluoroapatite reacts more thoroughly, but it also leads to the leaching of rare earth oxide, resulting in an increase in the loss rate of rare earth, which reduces the yield of rare earth elements in the subsequent leaching of rare earth.

Compared with Example 7, when the mineral particle size is coarser after roasting, the efficiency of phosphorus and fluorine removal is poor. This is because the rare earth oxide and fluoroapatite, the reaction products generated during roasting, are mutually wrapped. During the phosphorus and fluorine removal reaction, the fluoroapatite wrapped in the rare earth oxide is difficult to contact with hydrochloric acid, resulting in incomplete reaction, thereby reducing the removal rate of phosphorus and fluorine.

Therefore, according to the comparison between the above embodiments and comparative examples, it can be seen that the parameters in the process of the present invention have an appropriate range, and exceeding the range will correspondingly reduce the yield of the element.

The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (3)

1. The hydrochloric acid treatment process of the mixed rare earth concentrate is characterized by comprising the following steps of:

Mixing and roasting mixed rare earth concentrate and a calcium-containing compound, grinding to obtain finely ground mineral, leaching the finely ground mineral with hydrochloric acid of a first concentration to decompose fluorapatite, leaching phosphorus into leaching liquid to generate phosphoric acid, filtering to obtain leaching liquid after leaching is finished, extracting and recovering phosphorus, generating hydrogen fluoride gas by fluorine, condensing the hydrogen fluoride gas to obtain hydrofluoric acid, realizing the recovery of phosphorus and fluorine, taking leached filter residues, adding undigested rare earth oxide into the filter residues, and leaching with hydrochloric acid of a second concentration to obtain rare earth chloride; the second concentration is greater than the first concentration;

the temperature of the mixed roasting is 950-1100 ℃ and the time is 1.5-3h;

The concentration of the first concentration hydrochloric acid is 1-2mol/L, and the concentration of the second concentration hydrochloric acid is 4-7mol/L;

the calcium-containing compound is CaO and/or CaCO ₃;

leaching with hydrochloric acid of a first concentration at a solid-liquid ratio of 1:2-4 for 15-30min at room temperature;

the solid-liquid ratio of the second concentration hydrochloric acid leaching is 1:3-6, and leaching is carried out for 1.5-3h at 60-85 ℃.

2. The hydrochloric acid treatment process of mixed rare earth concentrate according to claim 1, wherein the mass ratio of the mixed rare earth concentrate to the calcium-containing compound is 100:15-20.

3. The hydrochloric acid treatment process of mixed rare earth concentrate according to claim 1, wherein the mixed rare earth concentrate and the calcium-containing compound are mixed and roasted and ground to 300 mesh or less.