Treatment method of rare earth concentrate

Abstract

The invention relates to the technical field of rare earth ore concentrate treatment, in particular to a rare earth ore concentrate treatment method. The treatment method of the rare earth concentrate comprises the following steps that the rare earth concentrate, a calcium-containing compound, silicon dioxide and carbon powder are mixed and roasted, and roasted ore is obtained; water is added into the roasted ore for size mixing, and size is obtained; and acid is added into the slurry for reaction, solid-liquid separation is carried out, and acid leaching residues and rare earth chloride feed liquid are obtained. The method has the advantages of being simple in technological process, high in rare earth recovery rate, short in reaction time, environmentally friendly, low in cost and diversified in rare earth grade applicability. The silicon dioxide can increase the decomposition activity of bastnaesite and monazite in the rare earth ore, rare earth compounds easy to leach can be generated, and therefore the decomposition rate of the rare earth ore concentrate is increased, and calcium can also play a role in fixing fluorine. According to the method, the rare earth decomposition rate is 98% or above, and the rare earth leaching rate is 96% or above.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth concentrate processing, and in particular to a method for processing rare earth concentrate. Background Art

[0002] At present, there are three main types of mineral rare earth ores that can be mined: fluorocarbon cerium ore, monazite and mixed rare earth concentrate. The industrialized mixed rare earth concentrate decomposition technologies mainly include concentrated sulfuric acid high-temperature roasting decomposition process and concentrated alkali solution normal pressure decomposition process. However, the concentrated sulfuric acid high-temperature roasting decomposition process produces a large amount of high-temperature mixed acid tail gas, and the transformation sulfate wastewater and radioactive waste residue are difficult to treat, resulting in a huge and costly entire environmental protection treatment engineering system. The concentrated alkali solution decomposition process treats mixed rare earth concentrates with a REO grade of about 60%. The rare earth minerals are decomposed by sodium hydroxide, and a large amount of mixed alkali wastewater is produced, which is difficult to recycle and causes excessive waste of sodium hydroxide. It can only be simply neutralized and discharged into the sea after reaching the standard. It is impossible to recycle resources such as fluorine and phosphorus, and the grade of rare earth concentrate is required to be high. Fluorocarbon cerium ore mainly adopts the oxidation roasting-hydrochloric acid leaching-alkali conversion process, but the process is long and the acid and alkali consumption is large.

[0003] CN109988903A discloses a method for decomposing high-grade mixed rare earth concentrate by two-stage roasting with concentrated sulfuric acid. The rare earth concentrate and concentrated sulfuric acid are first mixed in a weight ratio of 1:1.3, then low-temperature roasting is performed at about 380°C to obtain low-temperature roasted ore, and the low-temperature roasted ore is high-temperature roasted at about 900°C to obtain high-temperature roasted ore; this method has a long process flow, consumes a large amount of concentrated sulfuric acid, and has high requirements on the grade of the mixed rare earth concentrate.

[0004] CN112981146A discloses a method for recovering rare earth molten salt electrolytic slag by solid fluorine transformation roasting. First, the fluorine-containing rare earth molten salt electrolytic slag is finely ground to a product particle size of less than 100 mesh, then mixed evenly with additives and then solid fluorine roasted for about 3 hours, and the roasted ore is subjected to acid leaching experiment to obtain acid leaching slag and acid leaching liquid. This method has high requirements on slag particle size, too long roasting time, and long process flow, which is not conducive to industrial production.

[0005] CN113564343A discloses a green chemical alkali-to-defluorination method for roasting fluorine-containing rare earth ores and solid slag. The method includes the steps of conventional alkali-to-defluorination of roasting fluorine-containing rare earth ores and slag, heating to extract NaF, solid-liquid separation and heating to extract rare earths, etc. Although the method can realize green chemical defluorination, it is not easy to realize industrial production due to the long process flow.

[0006] CN103184332A discloses a method for converting and decomposing fluorocarbon cerium rare earth ore by roasting a calcium compound and a masking agent. In this method, fluorocarbon cerium ore is mixed with a calcium compound, the exposed surface is covered with a masking agent, and then roasted at 800°C to 900°C for 2 to 5 hours. After roasting, hydrochloric acid is added for leaching. In this method, the fluorocarbon cerium ore reacts with calcium to form calcium fluoride, but due to the solid-solid reaction, the rare earth conversion rate is poor.

[0007] CN109837385A discloses a method for heating, melting, converting and decomposing rare earth ores. The invention uses monazite as a raw material, mixes it with petroleum coke and decomposes the monazite by heating it in an electric arc furnace. The monazite is decomposed by the principle of carbon thermal reduction, but the mixed rare earth concentrate is not analyzed.

[0008] CN115637339A discloses a production process for extracting phosphorus products and rare earth products from monazite rare earth ore. The invention mixes monazite with carbon powder and adds a binder to make balls, reacts at above 1400°C, and the generated tail gas is oxidized and reacts with hot water to produce phosphoric acid. The smelted ore is dissolved in hydrochloric acid to obtain a rare earth chloride solution. The invention only studies monazite and obtains phosphorus and rare earth oxides based on the principle of carbon thermal reduction of monazite.

[0009] CN110684896A discloses a high-temperature smelting method for decomposing bastnaesite, wherein bastnaesite is mixed with a reducing agent to form a ball and then smelted, an arc-starting material is provided in the smelting equipment, and an inert gas is injected during smelting, and the inert gas is preferably argon. However, the temperature is above 2000°C, which places high demands on the equipment. Summary of the invention

[0010] Based on the above content, the present invention provides a method for processing rare earth concentrate with simple process flow, high rare earth recovery rate, short reaction time, green environmental protection, low cost and diversified rare earth grade applicability.

[0011] To achieve the above object, the present invention provides the following solutions:

[0012] The present invention provides a method for treating rare earth concentrate, comprising the following steps:

[0013] The rare earth concentrate is mixed with a calcium compound, silicon dioxide and carbon powder and roasted to obtain a roasted ore;

[0014] Adding water to the roasted ore to prepare slurry;

[0015] Acid is added to the slurry to react, and the solid and liquid are separated to obtain acid leaching residue and rare earth chloride liquid.

[0016] In some embodiments of the present invention, the rare earth concentrate is at least one of bastnaesite, monazite, and mixed rare earth concentrate;

[0017] Calculated as REO, the rare earth content in the rare earth concentrate is not less than 40wt%.

[0018] In some embodiments of the present invention, the calcium-containing compound is at least one of calcium oxide, calcium hydroxide, calcium sulfate and calcium carbonate;

[0019] Calculated in terms of REO, the amount of the calcium-containing compound added is 0-40% of the mass of the rare earth in the rare earth concentrate, preferably 10-40%, more preferably 30-40%.

[0020] In some embodiments of the present invention, the amount of silicon dioxide added is 5% to 60% of the mass of the rare earth in the rare earth concentrate, calculated as REO, preferably 10% to 50%, and more preferably 20% to 40%.

[0021] In some embodiments of the present invention, the amount of the carbon powder added is 10% to 40% of the mass of the rare earth in the rare earth concentrate, calculated as REO, preferably 10% to 30%, and more preferably 20% to 30%.

[0022] In some embodiments of the present invention, the calcination temperature is 1400°C to 1700°C, and the calcination time is 0.5h to 4h. The calcination temperature is preferably 1500°C to 1700°C, more preferably 1600°C to 1700°C; the calcination time is preferably 2 to 4h, more preferably 3 to 4h.

[0023] At this roasting temperature, the materials are in a molten state, which allows the materials to be mixed evenly. After the roasting is completed and the materials are cooled, they are transformed into rare earth compounds that are easily soluble in hydrochloric acid.

[0024] The addition of carbon powder allows the roasting process to be carried out under a reducing atmosphere.

[0025] In the present invention, the addition of silicon dioxide can increase the phase transformation of rare earth concentrate during the roasting process. The rare earth concentrate (including bastnaesite or monazite ore) is transformed into easy-to-leach rare earth silicate by the simultaneous action of silicon dioxide. The rare earth in the rare earth concentrate is more easily leached under the action of silicon dioxide, thereby improving the leaching efficiency of the rare earth.

[0026] Prior to the present application, no one had realized that the addition of silicon dioxide had such an impact on the rare earth leaching rate in mixed rare earth concentrates, fluorocarbon cerium ore and monazite ore. The present application unexpectedly discovered that the rare earth leaching rate can be increased to more than 96% by adding silicon dioxide, and the process is simple. The rare earth chloride solution can be directly obtained by acid leaching in one step, and the obtained acid leaching residue can be returned for roasting, which significantly reduces the amount of waste residue.

[0027] The existing technology only focuses on the decomposition of fluorocarbonates. Compared with the present technology, the decomposed minerals include mixed rare earth concentrates, fluorocarbon cerium ore or monazite ore, and the minerals are more complex. In comparison, monazite ore belongs to rare earth phosphate, has a stable structure, and is more difficult to decompose. The addition of silicon dioxide can increase the mineral phase transformation of monazite minerals, making it easier to leach rare earths in monazite minerals. The method of the present invention is highly applicable to minerals.

[0028] Before acid leaching the roasted ore, the method further includes grinding the roasted ore, preferably grinding the ore to 100 mesh.

[0029] In some embodiments of the present invention, the solid-to-liquid ratio of the roasted ore to the water is 1:4-6 (g / mL); more preferably 1:5.

[0030] The temperature of the slurry is 30-80° C. The temperature of the slurry is adjusted by heating or by limiting the temperature of water; the temperature of the slurry is preferably 40-70° C., more preferably 50-60° C.

[0031] In some embodiments of the present invention, the acid is hydrochloric acid; the amount of the acid added is such that the hydrogen ion concentration in the reaction system is 0.2 to 0.8 mol / L.

[0032] In some embodiments of the present invention, the reaction temperature is 30-80°C, and the reaction time is 0.5-2 hours, preferably 1-2 hours, and more preferably 2 hours.

[0033] The acid leaching slurry is subjected to solid-liquid separation operation to obtain acid leaching residue and rare earth chloride liquid. The acid leaching residue can be returned to roasting. Under the conditions of the present invention, the rare earth in the rare earth concentrate can be extracted into the acid leaching liquid to the maximum extent, and the REO leaching rate is ≥96%.

[0034] Solid-liquid separation can be selected from centrifugation or filtration, preferably filtration.

[0035] The present invention provides a method for treating rare earth concentrates with simple process flow, high rare earth recovery rate, short reaction time, green environmental protection, low cost and diversified rare earth grade applicability. The silicon dioxide used in the method of the present invention can increase the decomposition activity of bastnaesite and monazite in rare earth ores, generate rare earth compounds that are easily leached, thereby improving the decomposition rate of rare earth concentrates, and calcium can also play a role in fluorine fixation. The generated calcium fluoride can also be recycled and reused, and there is no pollution to the atmosphere and water bodies. The present invention saves energy, reduces energy consumption, shortens the process flow, and the rare earth decomposition rate is above 98%, and the rare earth leaching rate is above 96%. The above advantages can save energy for enterprises, reduce energy consumption and make full use of mineral resources.

[0036] The present invention discloses the following technical effects:

[0037] (1) The present invention increases the decomposition activity of bastnaesite and monazite in rare earth ores by adding silicon dioxide, thereby promoting the decomposition of bastnaesite and monazite to generate rare earth silicates.

[0038] (2) The present invention preferentially leaches rare earth by regulating the hydrochloric acid leaching conditions, does not generate waste water, and the acid leaching residue can continue to return to the source for further reaction, which can significantly reduce the amount of waste residue.

[0039] (3) The present invention does not limit the particle size of the mineral, reduces the grinding process, and broadens the scope of rare earth mineral smelting.

[0040] (4) Compared with the existing high-temperature decomposition process, the present invention has strong applicability to minerals and can decompose single bastnaesite, single monazite and mixed rare earth concentrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 The figure is a process flow chart of the rare earth concentrate treatment of the present invention. DETAILED DESCRIPTION

[0043] 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.

[0044] It should be understood that the terms described in the present invention are only for describing a particular embodiment 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. The intermediate value in any stated value or stated range, and each smaller range between 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.

[0045] 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.

[0046] 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 the skilled artisan. The present invention description and examples are exemplary only.

[0047] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0048] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0049] The processing flow chart of the rare earth concentrate of the present invention is as follows Figure 1 shown.

[0050] The analysis method involved in the present invention is:

[0051] REO (rare earth oxide) content: analyzed by weight method.

[0052] F content: analyzed by distillation method.

[0053] CaO content: analyzed by EDTA titration method.

[0054] The calculation formula of the rare earth leaching rate in the present invention=(mass of REO in the rare earth leaching solution / mass of REO in the rare earth concentrate)×100%.

[0055] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0056] The hydrochloric acid used in the embodiments of the present invention is industrial hydrochloric acid with a mass concentration of 30% to 36%.

[0057] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0058] Example 1

[0059] 50g of mixed rare earth concentrate (REO content of 57.56%, the main rare earth elements in REO are CeO2 accounting for 50.74%, La2O3 accounting for 27.91%, Pr6O 11 4.83%, Nd2O3 14.44%, CaO 8.33%, SiO2 0.76%, F 5.99%) and 30% silica (calculated as rare earth oxide, i.e., the amount of silica added accounts for 30% of the mass of rare earth oxide), 30% calcium oxide (calculated as rare earth oxide) and 20% carbon powder (calculated as rare earth oxide) are mixed in a graphite crucible, and the crucible is placed in a muffle furnace and roasted at 1550°C for 2h. After the roasting, the roasted ore is obtained. After the roasted ore is ground to 100 mesh, 200mL of water is added to the slurry and heated to 40°C. 50mL of hydrochloric acid is slowly added to the slurry after the liquid is slurried for 2h. After the reaction is completed, solid-liquid separation is performed to obtain acid leaching residue and chloride rare earth feed liquid. By calculation, the REO leaching rate is 96.89%, the CeO2 leaching rate is 97.02%, the La2O3 leaching rate is 96.62%, and the Pr6O 11 The leaching rate is 97.05% and the Nd2O3 leaching rate is 97.58%.

[0060] Example 2

[0061] The only difference from Example 1 is that the rare earth concentrate used is Shandong Weishan fluorocarbon cerium rare earth concentrate (REO content is 42.76%, and the main rare earth element ratio in REO is CeO2 accounting for 49.47%, La2O3 accounting for 31.63%, Pr6O 11 The rare earth leaching solution was analyzed and tested, and the leaching rate is shown in Table 1.

[0062] Example 3

[0063] The only difference from Example 1 is that the rare earth concentrate used is monazite ore (REO content is 63.21%, and the main rare earth element ratio in REO is CeO2 accounting for 51.62%, La2O3 accounting for 25.53%, Pr6O 11 The rare earth leaching solution was analyzed and tested, and the leaching rate is shown in Table 1.

[0064] Example 4

[0065] The only difference from Example 1 is that 20% SiO2 (calculated as rare earth oxide), 40% Ca(OH)2 (calculated as rare earth oxide), and 10% carbon powder (calculated as rare earth oxide) are added, the roasting temperature is 1500°C, and the roasting time is 2 hours. The remaining steps and parameters are the same as those in Example 1. The rare earth leaching solution is analyzed and tested, and the leaching rate is shown in Table 1.

[0066] Comparative Example 1

[0067] The only difference from Example 1 is that SiO2 is not added, and the remaining steps and parameters are the same as those of Example 1. The rare earth leaching solution was analyzed and tested, and the leaching rate is shown in Table 1.

[0068] Comparative Example 2

[0069] The only difference from Example 1 is that 5% SiO2 (calculated as rare earth oxide) is added, and the remaining steps and parameters are the same as those of Example 1. The rare earth leaching solution is analyzed and tested, and the leaching rate is shown in Table 1.

[0070] It can be seen from Comparative Examples 1 and 2 that when no or a small amount of silicon dioxide is added to the rare earth concentrate, the leaching rate of rare earth drops sharply. This shows the importance of silicon dioxide in promoting the leaching of rare earth in the rare earth concentrate in the technical solution of the present invention.

[0071] Table 1 Experimental data of different implementation cases

[0072]

[0073] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for treating rare earth concentrate, characterized in that: The following steps are involved: The rare earth concentrate is mixed with a calcium compound, silicon dioxide and carbon powder and roasted to obtain a roasted ore; Adding water to the roasted ore to prepare slurry; Acid is added to the slurry to react, and the solid and liquid are separated to obtain acid leaching residue and rare earth chloride liquid.

2. The method for treating rare earth concentrate according to claim 1, characterized in that: The rare earth concentrate is at least one of bastnaesite, monazite, and mixed rare earth concentrate; Calculated as REO, the rare earth content in the rare earth concentrate is not less than 40wt%.

3. The method for treating rare earth concentrate according to claim 1, characterized in that: The calcium-containing compound is at least one of calcium oxide, calcium hydroxide, calcium sulfate and calcium carbonate; Calculated in terms of REO, the added amount of the calcium-containing compound accounts for 0 to 40% of the mass of the rare earth in the rare earth concentrate.

4. The method for treating rare earth concentrate according to claim 1, characterized in that: Calculated in terms of REO, the added amount of silicon dioxide accounts for 5% to 60% of the mass of the rare earth in the rare earth concentrate.

5. The method for treating rare earth concentrate according to claim 1, characterized in that: Calculated in terms of REO, the added amount of the carbon powder accounts for 10% to 40% of the mass of the rare earth in the rare earth concentrate.

6. The method for treating rare earth concentrate according to claim 1, characterized in that: The calcination temperature is 1400° C. to 1700° C., and the calcination time is 0.5 h to 4 h.

7. The method for treating rare earth concentrate according to claim 1, characterized in that: The solid-liquid ratio of the roasted ore to the water is 1:4-6; The temperature of the slurry is 30-80°C.

8. The method for treating rare earth concentrate according to claim 1, characterized in that: The acid is hydrochloric acid; the amount of the acid added is such that the hydrogen ion concentration in the reaction system reaches 0.2-0.8 mol / L.

9. The method for treating rare earth concentrate according to claim 1, characterized in that: The reaction temperature is 30-80° C. and the reaction time is 0.5-2 hours.

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