Mixed rare earth concentrate gradient chemical separation and resource comprehensive recovery method

Abstract

The invention discloses a mixed rare earth concentrate gradient chemical separation and resource comprehensive recovery method which comprises the following steps: 1) primary reaction: reacting mixed rare earth concentrate with hydrochloric acid, and carrying out solid-liquid separation to obtain primary chemical separation ore and primary chemical separation liquid; 2) second-stage reaction: reacting the first-stage chemical separation liquid with mixed rare earth concentrate, adding a calcium-containing inorganic compound into a reaction system after the reaction is finished, continuously reacting, and performing solid-liquid separation to obtain second-stage chemical separation ore and second-stage chemical separation liquid; 3) chemical separation liquid recovery reaction: reacting the secondary chemical separation liquid with rare earth chloride to obtain phosphoric acid rare earth solid and a calcium chloride solution; (4) a third-stage reaction is conducted, specifically, the second-stage mineral separation reacts with hydrochloric acid, solid-liquid separation is conducted, and third-stage mineral separation and third-stage chemical separation liquid are obtained; wherein the content of CaO in the mixed rare earth concentrate in the step 1) and the step 2) is 5-15 wt%; and the third-stage chemical separation is chemical separation concentrate. According to the method, calcium can be removed, calcium resources can be recycled, meanwhile, the rare earth yield can be larger than or equal to 99.5%, and comprehensive recycling of the resources is achieved.

Description

Technical Field

[0001] The invention relates to a method for gradient separation of mixed rare earth concentrate and comprehensive resource recovery. Background Art

[0002] The Bayan Obo mixed rare earth concentrate, primarily composed of bastnaesite, monazite, fluorite, apatite, and associated minerals such as hematite, is considered difficult to smelt. Due to variations in beneficiation processes, flotation reagents, and on-site operations, the proportions of bastnaesite and monazite in the resulting mixed rare earth concentrate vary, as does the content of associated minerals such as fluorite and apatite. Because the concentrate primarily consists of two minerals, bastnaesite and monazite, its processing differs from that of single bastnaesite and monazite. In recent years, the most studied methods for decomposing mixed rare earth concentrates include concentrated sulfuric acid roasting, liquid caustic soda decomposition of monazite, sulfuric acid slurry decomposition of bastnaesite, and high-temperature chlorination decomposition. Currently, concentrated sulfuric acid roasting and caustic soda decomposition are the primary processes used in industrial production at the Bayan Obo mine.

[0003] Roasting with concentrated sulfuric acid is the most classic process for decomposing rare earth concentrate. It is widely used in the extraction of rare earths from Bayan Obo mixed rare earth concentrate due to its simple process, convenient operation, high rare earth recovery rate, low requirements for rare earth grade, and suitability for large-scale continuous production.

[0004] In the liquid alkali decomposition process for mixed rare earth concentrate, the concentrate is first pretreated with hydrochloric acid and sodium sulfate at a low boiling temperature for 4-6 hours. This removes impurities such as calcium and iron, reduces rare earth loss, and ultimately increases the REO grade to over 65%. The treated concentrate is then heated and decomposed with liquid alkali. This method achieves extremely low REO loss. However, a significant amount of highly acidic calcium removal wastewater is directly neutralized with the alkaline wastewater from the alkaline decomposition process before being discharged, leaving the residual acid unutilized. The enriched high-grade concentrate contains sodium sulfate and rare earth sulfate complex salts. The presence of sodium ions prevents the mineral from being treated using sulfuric acid decomposition. Otherwise, complex salts of sodium and rare earths would precipitate during water leaching after sulfuric acid decomposition, reducing the rare earth yield. Furthermore, as the water is recycled, sodium is further concentrated, further reducing the rare earth recovery rate.

[0005] CN105668888B discloses a method for the comprehensive recovery of low-grade mixed rare earth concentrate and wastewater resources. The method uses a hydrochloric acid solution and an enhanced impurity remover to mix the low-grade concentrate for chemical separation. The chemical separation wastewater is then added with a sulfuric acid solution to remove calcium ions, forming calcium sulfate dihydrate. After decalcification, the chemical separation wastewater is recycled to treat the low-grade mixed rare earth concentrate. After the circulating chemical separation wastewater is decalcified, it is neutralized in steps with ammonia water or liquid ammonia to recover iron, rare earth, phosphorus enrichment and crude calcium fluoride byproduct respectively. The wastewater is evaporated and concentrated to obtain ammonium chloride crystals and distilled water. This method has obvious advantages in comprehensive resource recovery and acid and alkali consumption, but an enhanced impurity remover needs to be introduced during the reaction to remove calcium. At the same time, the calcium removal effect is poor, and the CaO content in the final chemical separation is still around 2.5%. At the same time, the process of recovering rare earths from chemical separation wastewater is relatively complex and difficult to industrialize.

[0006] CN108559842B discloses a method for leaching calcium and strontium from Weishan Lake rare earth concentrate using low-concentration hydrochloric acid. The method involves soaking the Weishan Lake rare earth concentrate with low-concentration hydrochloric acid and heating it for reaction. After the reaction is complete, the leaching solution is filtered, and Weishan Lake rare earth concentrate is added again to the filtered leachate, heated for reaction, and the resulting liquid is discharged after solid-liquid separation, with the solid phase reused. This method can substantially remove calcium carbonate from the Weishan Lake rare earth concentrate, but it is only suitable for treating calcium-containing impurities, primarily calcite, in the Weishan Lake rare earth concentrate. It cannot remove calcium-containing impurities such as fluorite and apatite in mixed rare earth concentrates. Furthermore, to ensure effective calcium removal, the liquid-to-solid ratio during the reaction is large, generating a large amount of chemical separation wastewater. This increases the cost of treating the wastewater and makes industrialization difficult.

[0007] CN117802312A discloses a chemical beneficiation method for improving the quality and reducing the calcium content of a mixed rare earth concentrate. The method primarily includes chemical leaching, separation, and optional drying, with the chemical leaching being carried out in two stages. This method reduces the calcium oxide content in the rare earth concentrate and improves the grade of the mixed rare earth concentrate. However, this method has a significant problem: while the calcium oxide content in the rare earth concentrate can be reduced to approximately 1%, the rare earth yield is only around 95%. In the context of the growing value of rare earths, this undoubtedly reduces the utilization value of rare earths and increases production costs.

[0008] CN106801153A discloses a low-cost method for enriching high-grade mixed rare earth concentrate, characterized by: leaching a rare earth concentrate with a rare earth grade of 40 to 65 at% obtained by flotation with a low-concentration hydrochloric acid solution at room temperature, separating to obtain a primary chemical separation and chemical separation wastewater, heating and leaching the primary chemical separation with a newly prepared hydrochloric acid solution, washing and separating to obtain a chemical separation concentrate and a secondary first-level chemical separation solution, further heating and leaching a new primary chemical separation solution with the secondary first-level chemical separation solution, washing and separating to obtain a chemical separation concentrate and a secondary second-level chemical separation solution, and repeating this cycle to separate the primary chemical separation and the primary second-level chemical separation solution. Although this method can remove calcium, the process of chemical separation and calcium removal using this method causes a large amount of rare earth and phosphorus to enter the chemical separation solution, resulting in a waste of rare earth resources and making it impossible to achieve comprehensive resource recovery and utilization. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a method for gradient beneficiation of mixed rare earth concentrate and comprehensive resource recovery, which can remove calcium and recover calcium resources, with less rare earth loss, high rare earth recovery rate, simple operation, and can recover phosphate and calcium chloride solution separately, thereby realizing comprehensive resource recovery and utilization.

[0010] The present invention achieves the above-mentioned purpose through the following technical solutions.

[0011] The present invention provides a method for gradient separation of mixed rare earth concentrate and comprehensive resource recovery, comprising the following steps:

[0012] 1) Primary reaction: reacting the mixed rare earth concentrate with hydrochloric acid, separating the solid and liquid, and obtaining primary chemical separation and primary chemical separation liquid;

[0013] 2) Secondary reaction: The primary beneficiation liquid is reacted with the mixed rare earth concentrate. After the reaction is completed, a calcium-containing inorganic compound is added to the reaction system to continue the reaction, and the solid-liquid separation is performed to obtain the secondary beneficiation liquid;

[0014] 3) Recycling the chemical separation liquid: reacting the secondary chemical separation liquid with rare earth chloride to obtain rare earth phosphate solid and calcium chloride solution;

[0015] 4) Tertiary reaction: react the secondary ore dressing with hydrochloric acid, separate the solid and liquid, and obtain tertiary ore dressing and tertiary ore dressing liquid;

[0016] Wherein, the CaO content in the mixed rare earth concentrate in step 1) and step 2) is 5-15wt%; the tertiary chemical separation is the chemical separation concentrate.

[0017] The method according to the present invention preferably further comprises the following steps:

[0018] Four-stage reaction: replace the first-stage chemical separation liquid with the third-stage chemical separation liquid and repeat the reaction in step 2) to obtain the fourth-stage chemical separation liquid and the fourth-stage chemical separation;

[0019] Recycling the chemical separation solution: replacing the secondary chemical separation solution with the quaternary chemical separation solution and repeating the reaction in step 3) to obtain rare earth phosphate solid and calcium chloride solution;

[0020] Five-stage reaction: replace the secondary chemical separation with the quaternary chemical separation and repeat the reaction in step 4) to obtain five-stage chemical separation and five-stage chemical separation liquid; wherein, the five-stage chemical separation is chemical separation concentrate.

[0021] The method according to the present invention preferably further comprises the following steps:

[0022] n-level reaction: replace the first-level chemical separation solution with the n-1-level chemical separation solution and repeat the reaction in step 2) to obtain the n-level chemical separation solution and n-level chemical separation;

[0023] Recycling the chemical separation solution: replacing the secondary chemical separation solution with the n-level chemical separation solution and repeating the reaction in step 3) to obtain rare earth phosphate solid and calcium chloride solution;

[0024] n+1-level reaction: replace the secondary chemical separation with the n-level chemical separation and repeat the reaction in step 4) to obtain n+1-level chemical separation and n+1-level chemical separation solution;

[0025] Wherein, n is an even number greater than or equal to 6;

[0026] Among them, n+1 level chemical separation is chemical separation concentrate;

[0027] Among them, the n+1 level chemical selection liquid is further processed with reference to the n-1 level chemical selection liquid.

[0028] According to the method of the present invention, preferably, in step 1), the concentration of hydrochloric acid is 5-8 mol / L, and the liquid-solid ratio of hydrochloric acid to mixed rare earth concentrate is 0.8-2 mL:1 g.

[0029] According to the method of the present invention, preferably, in step 1), the reaction temperature is 80-95° C., and the reaction time is 60-180 min.

[0030] According to the method of the present invention, preferably, in step 2), the liquid-to-solid ratio of the primary chemical separation liquid to the mixed rare earth concentrate is 0.8-2 mL:1 g; and the calcium-containing inorganic compound is selected from at least one of calcium carbonate, calcium oxide and calcium hydroxide.

[0031] According to the method of the present invention, preferably, in step 2), the amount of the calcium-containing inorganic compound added is 1 to 5 wt% of the mass of the mixed rare earth concentrate.

[0032] According to the method of the present invention, preferably, in step 3), the REO content of the secondary dressing solution is less than 1 g / L; and the rare earth element in the rare earth chloride is selected from at least one of lanthanum, praseodymium, neodymium and cerium.

[0033] According to the method of the present invention, preferably, in step 4), the concentration of hydrochloric acid is 5 to 8 mol / L; the weight of the secondary mineral processing is calculated based on the weight of the mixed rare earth concentrate in step 2), and the liquid-solid ratio of hydrochloric acid to secondary mineral processing is 0.8 to 2 mL: 1 g.

[0034] According to the method of the present invention, preferably, in step 4), the reaction temperature is 10-90° C., and the reaction time is 60-180 min.

[0035] The method of the present invention not only achieves deep separation of calcium and rare earth through a gradient chemical separation process, but also allows the supernatant rare earth to enter the slag for recovery by regulating the acidity of the chemical separation solution (the acidity of the chemical separation solution is reduced by adding calcium oxide. The low acidity allows the rare earth and phosphorus in the chemical separation wastewater to undergo a precipitation reaction to form rare earth phosphate precipitates, thereby achieving the purpose of recovering rare earth). Unlike traditional chemical separation processes that recover rare earth by adding sodium sulfate, this process does not require the introduction of new substances (such as sodium sulfate) to recover rare earth, and can also achieve a rare earth yield of more than 99.5%. The method of the present invention can fully recover phosphorus lost during the chemical separation process, and can also obtain a high-concentration calcium chloride solution by regulating the chemical wastewater (i.e., the chemical separation solution), thereby fully recovering calcium resources in the chemical separation wastewater, saving the treatment cost of the chemical separation wastewater. In addition, the present invention reduces the amount of chemical separation wastewater through a low liquid-to-solid ratio reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0038] The present invention provides a method for gradient separation of mixed rare earth concentrate and comprehensive resource recovery, comprising the following steps: 1) a primary reaction of the mixed rare earth concentrate with hydrochloric acid; 2) a secondary reaction of the primary separation solution with the mixed rare earth concentrate; 3) recovery of the separation solution; and 4) a tertiary reaction of the secondary separation solution with hydrochloric acid. The method may also include a quaternary reaction step, a quinary reaction step, an n-stage reaction step, and an n+1-stage reaction step (where n is an even number greater than or equal to 6). A detailed description is provided below.

[0039] <Primary Reaction Step of Mixed Rare Earth Concentrate and Hydrochloric Acid>

[0040] The mixed rare earth concentrate is reacted with hydrochloric acid, followed by solid-liquid separation, to produce primary chemical separation and primary chemical separation liquid. This facilitates the removal of calcium-containing minerals. This process can partially remove calcium from the mixed rare earth concentrate and also provides initial activation for further calcium removal.

[0041] In the present invention, the mixed rare earth concentrate is primarily composed of bastnaesite and monazite, and also contains apatite, fluorite, and the like. The mass ratio of bastnaesite to monazite is greater than or equal to 2:1. The mixed rare earth concentrate of the present invention has an REO content greater than 40% by weight, a P2O5 content of 3-12% by weight, and a CaO content of 5-15% by weight. The mixed rare earth concentrate also contains the element F, with the F content ranging from 5-12% by weight, preferably from 7-10% by weight.

[0042] According to one embodiment of the present invention, in the mixed rare earth concentrate, the REO content is greater than 40wt% and less than 65wt%, the P2O5 content is 5-12wt%, and the CaO content is 6-13wt%. According to a specific embodiment of the present invention, in the mixed rare earth concentrate, the REO content is greater than 45wt% and less than 65wt%, the P2O5 content is 7-12wt%, and the CaO content is 6-11wt%.

[0043] In the primary reaction step, the main chemical reactions involved are:

[0044] 3REFCO3+6HCl=3CO2↑+3H2O+REF3+2RECl3; RE represents rare earth element;

[0045] CaF2+2HCl=CaCl2+2HF;

[0046] Ca5(PO4)3F+10HCl=5CaCl2+3H3PO4+HF. The generated HF can be absorbed by spraying to produce hydrofluoric acid.

[0047] In the present invention, the concentration of hydrochloric acid can be 5 to 8 mol / L, for example, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L. The liquid-to-solid ratio of hydrochloric acid to mixed rare earth concentrate is 0.8 to 2 mL:1 g, preferably 0.9 to 1.5 mL:1 g, and more preferably 0.9 to 1 mL:1 g. The reaction temperature of the mixed rare earth concentrate and hydrochloric acid can be 80 to 95° C., preferably 85 to 95° C., and more preferably 90 to 95° C. The reaction time can be 60 to 180 min, preferably 90 to 180 min, and more preferably 120 to 180 min. This is conducive to dissolving calcium in hydrochloric acid, increasing the REO content of the chemically separated concentrate, and reducing the calcium content in the chemically separated ore.

[0048] After the reaction is completed, solid-liquid separation is performed, and the solid-liquid separation can be centrifugation or filtration, preferably filtration, to obtain a primary chemical separation liquid and a primary chemical separation. In the present invention, the primary chemical separation can be reacted with 5-8 mol / L hydrochloric acid (the liquid-solid ratio of hydrochloric acid to the primary chemical separation is 0.8-2 mL: 1 g) at 10-90 ° C to obtain a low-calcium concentration concentrate, and the obtained chemical separation liquid can be used for the secondary reaction.

[0049] <Secondary reaction step of primary chemical separation solution and mixed rare earth concentrate>

[0050] The primary separation solution is then reacted with the mixed rare earth concentrate. After the reaction is complete, a calcium-containing inorganic compound is added to the reaction system to continue the reaction, and the solid-liquid separation is performed to obtain the secondary separation solution. This reuse of the primary separation solution not only provides preliminary treatment of the mixed rare earth concentrate, but also allows for better recovery of calcium chloride solution and phosphorus.

[0051] In this step, the mixed rare earth concentrate is primarily composed of bastnaesite and monazite, and also contains apatite, fluorite, and the like. The mass ratio of bastnaesite to monazite is greater than or equal to 2:1. The mixed rare earth concentrate of the present invention has an REO content greater than 40% by weight, a P2O5 content of 3-12% by weight, and a CaO content of 5-15% by weight. The mixed rare earth concentrate also contains the element F, with the F content being 5-12% by weight. The mixed rare earth concentrate in this step is essentially the same as the mixed rare earth concentrate used above.

[0052] The liquid-to-solid ratio of the primary chemical separation solution to the mixed rare earth concentrate can be 0.8-2 mL:1 g, preferably 0.9-1.5 mL:1 g, and more preferably 0.9-1 mL:1 g. The mixed rare earth concentrate in this step has substantially the same composition as the mixed rare earth concentrate in the primary reaction step, and the weight ratios of the two are preferably the same. The temperature for the reaction of the primary chemical separation solution with the mixed rare earth concentrate can be 50-95° C., preferably 60-90° C., and more preferably 80-90° C. The reaction time can be 60-180 min, preferably 90-180 min.

[0053] In the present invention, the calcium-containing inorganic compound is selected from at least one of calcium carbonate, calcium oxide or calcium hydroxide, preferably calcium oxide. In this step, the amount of the calcium-containing inorganic compound added is 1 to 5 wt% of the mass of the mixed rare earth concentrate, preferably 3 to 5 wt%, and more preferably 4 to 5 wt%. The addition of the calcium-containing inorganic compound can, on the one hand, reduce the acidity of the dressing liquid system so that the rare earth is preferentially precipitated for recovery, and on the other hand, increase the calcium concentration in the dressing liquid and facilitate the recycling of calcium resources. Ultimately, the REO in the secondary dressing liquid is less than or equal to 1 g / L, preferably less than 1 g / L. Specifically, the REO concentration in the secondary dressing liquid is 0.1 to 1 g / L, preferably 0.1 to 0.6 g / L.

[0054] <Recovery and Separation Liquid Step>

[0055] The secondary separation solution is reacted with rare earth chloride to produce rare earth phosphate solids and a calcium chloride solution. This allows phosphorus to be recovered, resulting in rare earth phosphate and a higher concentration calcium chloride solution. The high concentration calcium chloride solution can be evaporated and concentrated to produce a calcium chloride byproduct.

[0056] In this step, the rare earth element in the rare earth chloride can be selected from at least one of lanthanum, praseodymium, neodymium, and cerium, preferably lanthanum. According to one embodiment of the present invention, the rare earth chloride is lanthanum chloride. The amount of rare earth chloride added is 5-9 wt%, preferably 6-8 wt%, of the weight of the mixed rare earth concentrate in the secondary reaction step. The resulting calcium chloride solution can have a CaO content of up to 90 g / L.

[0057] In this step, the main chemical reactions involved are as follows:

[0058] RECl3+H3PO4=REPO4+3HCl.

[0059] <Secondary beneficiation and tertiary reaction steps of hydrochloric acid>

[0060] The secondary ore is reacted with hydrochloric acid, followed by solid-liquid separation, to produce a tertiary ore and a tertiary ore concentrate. This produces a tertiary ore concentrate with an REO content of 70% or greater by weight, known as a tertiary ore concentrate. The tertiary ore concentrate can then be used in the quaternary reaction.

[0061] In this step, the concentration of hydrochloric acid can be 5 to 8 mol / L, for example, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L. The secondary beneficiation is calculated based on the weight of the mixed rare earth concentrate in the secondary reaction step. The liquid-to-solid ratio of hydrochloric acid to secondary beneficiation is 0.8 to 2 mL:1 g, preferably 0.9 to 1.5 mL:1 g, and more preferably 0.9 to 1 mL:1 g. The reaction temperature of the secondary beneficiation and hydrochloric acid can be 10 to 90° C., preferably 50 to 90° C., and more preferably 80 to 90° C. The reaction time can be 60 to 180 min, preferably 90 to 180 min.

[0062] The CaO content of the obtained tertiary beneficiation product is 0.2-2wt%, preferably 0.5-1wt%, more preferably 0.5-0.6wt%; and the REO recovery rate can reach greater than or equal to 99.5wt%.

[0063] <Fourth-stage reaction step, recovery and selection liquid step, and fifth-stage reaction step>

[0064] The reaction of step 2) is repeated by replacing the primary chemical separation liquid with the tertiary chemical separation liquid to obtain a quaternary chemical separation liquid and a quaternary chemical separation liquid; the reaction of step 3) is repeated by replacing the secondary chemical separation liquid with the quaternary chemical separation liquid to obtain a rare earth phosphate solid and a calcium chloride solution; the reaction of step 4) is repeated by replacing the secondary chemical separation liquid with the quaternary chemical separation liquid to obtain a fifth-grade chemical separation liquid and a fifth-grade chemical separation liquid; wherein the fifth-grade chemical separation liquid is a chemical separation concentrate. In this way, the tertiary chemical separation liquid can be used to purify the mixed rare earth concentrate to obtain a chemical separation concentrate (i.e., the fifth-grade chemical separation liquid), while the tertiary chemical separation liquid is recycled to achieve comprehensive resource recovery.

[0065] Specifically, the fourth-stage reaction: reacting the third-stage chemical beneficiation solution with the mixed rare earth concentrate, adding a calcium-containing inorganic compound to the reaction system after the reaction is completed, and continuing the reaction, followed by solid-liquid separation to obtain the fourth-stage chemical beneficiation product and the fourth-stage chemical beneficiation solution;

[0066] Recovery of the chemical beneficiation solution reaction: reacting the fourth-stage chemical beneficiation solution with rare earth chloride to obtain rare earth phosphate solid and calcium chloride solution;

[0067] Fifth-stage reaction: reacting the fourth-stage chemical beneficiation product with hydrochloric acid, followed by solid-liquid separation to obtain the fifth-stage chemical beneficiation product and the fifth-stage chemical beneficiation solution.

[0068] The reaction temperature between the third-stage chemical beneficiation solution and the mixed rare earth concentrate is 50-95 °C, preferably 60-90 °C, more preferably 80-90 °C. The reaction time can be 60-180 min, preferably 90-180 min. The liquid-solid ratio of the third-stage chemical beneficiation solution to the mixed rare earth concentrate can be 0.8-2 mL:1 g, preferably 0.9-1.5 mL:1 g, more preferably 0.9-1 mL:1 g.

[0069] The calcium-containing inorganic compound is selected from at least one of calcium carbonate, calcium oxide, and calcium hydroxide, preferably calcium oxide. The addition amount of the calcium-containing inorganic compound is 1-5 wt% of the mass of the mixed rare earth concentrate, preferably 3-5 wt%, more preferably 4-5 wt%.

[0070] The rare earth element in the rare earth chloride can be selected from at least one of lanthanum, praseodymium, neodymium, and cerium, preferably lanthanum. According to a specific embodiment of the present invention, the rare earth chloride is lanthanum chloride. The REO concentration in the fourth-stage chemical beneficiation solution is 0.1-1 g / L, preferably 0.1-0.6 g / L. The weight ratio of the fourth-stage chemical beneficiation solution to the rare earth chloride is 60-100:5-9, preferably 80-100:6-8. The CaO content of the obtained calcium chloride solution can reach 90 g / L.

[0071] The concentration of hydrochloric acid can be 5-8 mol / L, for example, it can be 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L. Taking the weight of the fourth-stage chemical beneficiation product as the calculation basis with the weight of the mixed rare earth concentrate in the third-stage reaction, the liquid-solid ratio of hydrochloric acid to the fourth-stage chemical beneficiation product is 0.8-2 mL:1 g, preferably 0.9-1.5 mL:1 g, more preferably 0.9-1 mL:1 g. The reaction temperature between the fourth-stage chemical beneficiation product and hydrochloric acid can be 10-90 °C, preferably 50-90 °C, more preferably 80-90 °C. The reaction time can be 60-180 min, preferably 90-180 min. The CaO content of the obtained fifth-stage chemical beneficiation product is 0.2-2 wt%, preferably 0.5-1 wt%, more preferably 0.5-0.6 wt%.

[0072] <n-stage reaction step, recovery of the chemical beneficiation solution reaction step, and n+1-stage reaction step>

[0073] Replace the first-level chemical dressing liquid with the n-1-level chemical dressing liquid and repeat the reaction of step 2) to obtain the n-level chemical dressing liquid and the n-level chemical dressing liquid; replace the second-level chemical dressing liquid with the n-level chemical dressing liquid and repeat the reaction of step 3) to obtain rare earth phosphate solid and calcium chloride solution; replace the second-level chemical dressing liquid with the n-level chemical dressing and repeat the reaction of step 4) to obtain the n+1-level chemical dressing liquid and the n+1-level chemical dressing liquid; wherein, n is an even number greater than or equal to 6; the n+1-level chemical dressing liquid is the chemical dressing concentrate; the n+1-level chemical dressing liquid is further processed with reference to the n-1-level chemical dressing liquid. In this way, the chemical dressing liquid can be used to treat the mixed rare earth concentrate and recover the calcium chloride solution and phosphate; in this way, the chemical dressing can be further processed to obtain the chemical dressing concentrate. This is conducive to further improving the grade of the obtained chemical dressing concentrate (i.e., REO content)

[0074] In certain specific embodiments, n=6, i.e., the fifth-level chemical separation liquid is repeated with the reaction of step 2) to obtain a sixth-level chemical separation liquid and a sixth-level chemical separation ore; the sixth-level chemical separation liquid is repeated with the reaction of step 3) to obtain rare earth phosphate solid and calcium chloride solution; the sixth-level ore is repeated with the reaction of step 4) to obtain a seventh-level ore and a seventh-level chemical separation liquid.

[0075] In other specific embodiments, n=8, that is, the seventh-level chemical dressing liquid is repeated with the reaction of step 2) to obtain an eighth-level chemical dressing liquid and an eighth-level chemical dressing ore; the eighth-level chemical dressing liquid is repeated with the reaction of step 3) to obtain rare earth phosphate solid and calcium chloride solution; the eighth-level chemical dressing ore is repeated with the reaction of step 4) to obtain a ninth-level chemical dressing ore and a ninth-level chemical dressing liquid.

[0076] According to one embodiment of the present invention, n-level reaction: n-1-level chemical separation liquid is reacted with mixed rare earth concentrate, and after the reaction is completed, a calcium-containing inorganic compound is added to the reaction system to continue the reaction, and the solid-liquid is separated to obtain n-level chemical separation and n-level chemical separation liquid;

[0077] Recycling of chemical separation liquid: reacting the n-grade chemical separation liquid with rare earth chloride to obtain rare earth phosphate solid and calcium chloride solution;

[0078] n+1-level reaction: react the n-level chemical separation with hydrochloric acid, separate the solid and liquid, and obtain n+1-level chemical separation and n+1-level chemical separation liquid; wherein n is an even number greater than or equal to 6, and the n+1-level chemical separation liquid is further treated in the same manner as the n-1-level chemical separation liquid.

[0079] In the n-stage reaction step of the present invention, the process parameters are similar to those of the secondary reaction step. For example, the liquid-to-solid ratio of the n-1-stage chemical separation solution to the mixed rare earth concentrate is 0.8-2 mL:1 g, the reaction temperature is 10-90°C, and the reaction time is 60-180 min. The amount of the calcium-containing inorganic compound added is 1-5 wt% of the mass of the mixed rare earth concentrate. A detailed description is omitted here.

[0080] The concentration of REO in the n-stage chemical separation solution is 0.1-1 g / L, preferably 0.1-0.6 g / L. The process parameters of the chemical separation solution recovery reaction step are as described above and are not described in detail here.

[0081] In the n+1 stage reaction step of the present invention, the process parameters refer to the process parameters of the tertiary reaction step. For example, the concentration of hydrochloric acid can be 5-8 mol / L; the n-stage beneficiation is calculated based on the weight of the mixed rare earth concentrate in the n-stage reaction step. The liquid-solid ratio of hydrochloric acid to n-stage beneficiation is 0.8-2 mL:1 g, the reaction temperature can be 10-90 ° C, and the reaction time can be 60-180 min. Detailed description is not given here. The CaO content of the obtained n+1 stage beneficiation is 0.2-2 wt%, preferably 0.5-1 wt%, and more preferably 0.5-0.6 wt%; the REO content can reach greater than or equal to 99.5 wt%.

[0082] In the present invention, solid-liquid separation can be performed by centrifugation or filtration, preferably filtration.

[0083] <Analysis Method>

[0084] REO content in mixed rare earth concentrate and chemical beneficiation: analyzed by weight method.

[0085] F content in mixed rare earth concentrate: analyzed by distillation method.

[0086] P2O5 content in mixed rare earth concentrate: analyzed by bismuth phosphate molybdenum blue spectrophotometry.

[0087] CaO content in mixed rare earth concentrate: analyzed by weight method.

[0088] REO content in the chemical separation solution: analyzed by cerium determination method.

[0089] CaO content in the chemical separation solution: EDTA complexometric titration method.

[0090] Example 1

[0091] In the mixed rare earth concentrate of this embodiment, the REO content is 59.93wt%, the F content is 8.5wt%, the P2O5 content is 10.08wt%, and the CaO content is 8wt%.

[0092] Reference Figure 1 Flow diagram:

[0093] Primary reaction: 100 parts by weight of mixed rare earth concentrate is reacted with 6 mol / L hydrochloric acid (i.e., primary hydrochloric acid, solid-liquid ratio of 1g:1mL) at 95°C for 180 minutes. After the reaction is completed, the mixture is filtered to obtain a primary chemical separation solution and a primary chemical separation solution. The primary chemical separation solution is further treated with 5 mol / L hydrochloric acid at 90°C to obtain a low-calcium concentrate. The obtained chemical separation solution can be used for the secondary reaction.

[0094] Secondary reaction: react the primary dressing liquid with 100 parts by weight of mixed rare earth concentrate at 90°C for 90 minutes. After the reaction is completed, add 4.5 parts by weight of calcium oxide to the reaction system and continue to react for 90 minutes. After the reaction is completed, filter to obtain secondary ore dressing and secondary dressing liquid.

[0095] Reaction for recovering the secondary separation solution: 7 parts by weight of lanthanum chloride was added to the secondary separation solution to perform a precipitation reaction to recover phosphorus from the secondary separation solution, producing lanthanum phosphate solid and a calcium chloride solution. The calcium chloride solution contained approximately 90 g / L of CaO.

[0096] Tertiary reaction: The secondary beneficiation is reacted with 6 mol / L hydrochloric acid (i.e., tertiary hydrochloric acid, the amount of hydrochloric acid is based on the weight of the mixed rare earth concentrate in the above-mentioned secondary reaction, and the solid-liquid ratio is 1g:1mL) at 95°C for 180 minutes. After the reaction is completed, the tertiary beneficiation is filtered to obtain the tertiary beneficiation and tertiary beneficiation liquid. The tertiary beneficiation is a chemical concentrate, i.e., a low-calcium mixed rare earth concentrate.

[0097] Example 2

[0098] In the mixed rare earth concentrate of this embodiment, the REO content is 59.93wt%, the F content is 8.5wt%, the P2O5 content is 10.08wt%, and the CaO content is 8wt%. The units of parts by weight in this embodiment are the same as those in Example 1.

[0099] Reference Figure 1 Flow diagram:

[0100] Fourth-stage reaction: The tertiary dressing solution obtained in Example 1 was reacted with 100 parts by weight of mixed rare earth concentrate at 90° C. for 120 min, and then 3.6 parts by weight of calcium oxide was added to the reaction system and the reaction was continued for 60 min. After the reaction was completed, the solution was filtered to obtain a fourth-stage dressing solution and a fourth-stage dressing ore.

[0101] Recovery reaction of the chemical separation liquid: 9 parts by weight of lanthanum chloride is added to the fourth-stage chemical separation liquid to carry out a precipitation reaction to recover phosphorus in the fourth-stage chemical separation liquid to obtain lanthanum phosphate solid and calcium chloride solution.

[0102] Five-stage reaction: The four-stage chemical separation product is reacted with 7 mol / L hydrochloric acid (the amount of hydrochloric acid is based on the weight of the mixed rare earth concentrate in the four-stage reaction, and the solid-liquid ratio is 1g:1mL) at 95°C for 150 minutes. After the reaction is completed, the five-stage chemical separation product is filtered to obtain the five-stage chemical separation solution. The five-stage chemical separation product is a chemical separation concentrate, i.e., a low-calcium mixed rare earth concentrate.

[0103] Example 3

[0104] In the mixed rare earth concentrate of this embodiment, the REO content is 50.23wt%, the F content is 9.5wt%, the P2O5 content is 11.08wt%, and the CaO content is 13wt%. The units of weight parts in this embodiment are the same as those in Example 2.

[0105] Reference Figure 1 Flow diagram:

[0106] Sixth-stage reaction (n=6): The fifth-stage beneficiation liquid obtained in Example 2 was reacted with 100 parts by weight of a mixed rare earth concentrate at 90° C. for 120 min. 3.6 parts by weight of calcium oxide were added to the reaction system and the reaction was continued for 60 min. After the reaction was completed, the solution was filtered to obtain a sixth-stage beneficiation liquid and a sixth-stage beneficiation ore.

[0107] Recovery reaction of the chemical separation liquid: 6 parts by weight of lanthanum chloride is added to the sixth-stage chemical separation liquid to carry out a precipitation reaction to recover phosphorus in the sixth-stage chemical separation liquid to obtain lanthanum phosphate solid and calcium chloride solution.

[0108] Seventh-stage reaction: The sixth-stage chemical separation product is reacted with 8 mol / L hydrochloric acid (the amount of hydrochloric acid is based on the weight of the mixed rare earth concentrate in the sixth-stage reaction, and the solid-liquid ratio is 1g:1mL) at 95°C for 150 minutes. After the reaction is completed, the seventh-stage chemical separation product is filtered to obtain the seventh-stage chemical separation product and the seventh-stage chemical separation liquid. The seventh-stage chemical separation product is a chemical separation concentrate, i.e., a low-calcium mixed rare earth concentrate.

[0109] Table 1

[0110]

[0111] As can be seen from the table, the REO concentration in the chemical separation wastewater (such as secondary chemical separation liquid, quaternary chemical separation liquid, and sixth chemical separation liquid) can be less than 1g / L (the REO content in the chemical separation wastewater is 0.5g / L), and the REO content in the chemical separation wastewater per ton of mixed rare earth concentrate is 1m 3 It can be calculated that the REO yield in the resulting chemical dressing (e.g., tertiary, fifth, and seventh-stage chemical dressing) is greater than or equal to 99.5%. The calcium chloride solution in the chemical dressing wastewater is highly concentrated, with a CaO content of over 90 g / L. The resulting chemical dressing has a CaO content of less than 1% and an REO grade of over 70%, facilitating subsequent smelting.

[0112] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for gradient separation of mixed rare earth concentrate and comprehensive resource recovery, characterized in that: The following steps are involved: 1) Primary reaction: reacting the mixed rare earth concentrate with hydrochloric acid, separating the solid and liquid, and obtaining primary chemical separation and primary chemical separation liquid; 2) Secondary reaction: The primary beneficiation liquid is reacted with the mixed rare earth concentrate. After the reaction is completed, a calcium-containing inorganic compound is added to the reaction system to continue the reaction, and the solid-liquid separation is performed to obtain the secondary beneficiation liquid; 3) Recycling the chemical separation liquid: reacting the secondary chemical separation liquid with rare earth chloride to obtain rare earth phosphate solid and calcium chloride solution; 4) Tertiary reaction: react the secondary ore dressing with hydrochloric acid, separate the solid and liquid, and obtain tertiary ore dressing and tertiary ore dressing liquid; Wherein, the CaO content in the mixed rare earth concentrate in step 1) and step 2) is 5-15wt%; the tertiary chemical separation is the chemical separation concentrate.

2. The method according to claim 1, characterized in that The following steps are also included: Four-stage reaction: replace the first-stage chemical separation liquid with the third-stage chemical separation liquid and repeat the reaction in step 2) to obtain the fourth-stage chemical separation liquid and the fourth-stage chemical separation; Recycling the chemical separation solution: replacing the secondary chemical separation solution with the quaternary chemical separation solution and repeating the reaction in step 3) to obtain rare earth phosphate solid and calcium chloride solution; Five-stage reaction: replace the secondary chemical separation with the quaternary chemical separation and repeat the reaction in step 4) to obtain five-stage chemical separation and five-stage chemical separation liquid; wherein, the five-stage chemical separation is chemical separation concentrate.

3. The method according to claim 2, characterized in that The following steps are also included: n-level reaction: replace the first-level chemical separation solution with the n-1-level chemical separation solution and repeat the reaction in step 2) to obtain the n-level chemical separation solution and n-level chemical separation; Recycling the chemical separation solution: replacing the secondary chemical separation solution with the n-level chemical separation solution and repeating the reaction in step 3) to obtain rare earth phosphate solid and calcium chloride solution; n+1-level reaction: replace the secondary chemical separation with the n-level chemical separation and repeat the reaction in step 4) to obtain n+1-level chemical separation and n+1-level chemical separation solution; Wherein, n is an even number greater than or equal to 6; Among them, n+1 level chemical separation is chemical separation concentrate; Among them, the n+1 level chemical selection liquid is further processed with reference to the n-1 level chemical selection liquid.

4. The method according to claim 1, wherein In step 1), the concentration of hydrochloric acid is 5-8 mol / L, and the liquid-solid ratio of hydrochloric acid to mixed rare earth concentrate is 0.8-2 mL:1 g.

5. The method according to claim 1, characterized in that In step 1), the reaction temperature is 80-95° C., and the reaction time is 60-180 min.

6. The method according to claim 1, characterized in that In step 2), the liquid-to-solid ratio of the primary chemical separation solution to the mixed rare earth concentrate is 0.8-2 mL:1 g; and the calcium-containing inorganic compound is selected from at least one of calcium carbonate, calcium oxide and calcium hydroxide.

7. The method according to claim 1, characterized in that In step 2), the amount of the calcium-containing inorganic compound added is 1 to 5 wt% of the mass of the mixed rare earth concentrate.

8. The method according to claim 1, characterized in that In step 3), the REO content of the secondary chemical separation solution is less than 1 g / L; the rare earth element in the rare earth chloride is selected from at least one of lanthanum, praseodymium, neodymium and cerium.

9. The method according to claim 1, characterized in that In step 4), the concentration of hydrochloric acid is 5 to 8 mol / L; the weight of the secondary beneficiation is calculated based on the weight of the mixed rare earth concentrate in step 2), and the liquid-solid ratio of hydrochloric acid to the secondary beneficiation is 0.8 to 2 mL:1 g.

10. The method according to claim 1, characterized in that In step 4), the reaction temperature is 10-90° C., and the reaction time is 60-180 min.

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