Methods for the decomposition of mixed rare earth concentrates and comprehensive utilization of associated resources

Abstract

This invention discloses a method for the decomposition of mixed rare earth concentrate and the comprehensive utilization of associated resources, comprising the following steps: 1) reacting the mixed rare earth concentrate with hydrochloric acid solution A to obtain rough minerals and mother liquor; 2) reacting the rough minerals with hydrochloric acid solution B to obtain re-decomposed minerals and a first acid solution containing rare earth chloride; 3) reacting the re-decomposed minerals with alkaline solution C, separating the solid and liquid to obtain a first filter cake and a first filtrate; washing the first filter cake to obtain a first alkali cake and a first washing alkali solution; reacting the first alkali cake with a hydrochloric acid solution to obtain a first acid residue and a second acid solution containing rare earth chloride; 4) reacting the first acid residue with alkaline solution D, separating the solid and liquid to obtain a second filter cake and a second filtrate; washing the second filter cake to obtain a second alkali cake and a second washing alkali solution; reacting the second alkali cake with a hydrochloric acid solution to obtain a second acid residue and a third acid solution containing rare earth chloride. The method of this invention can separately recover rare earth, fluorine, phosphorus, and calcium.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for decomposing mixed rare earth concentrate and comprehensively utilizing associated resources. BACKGROUND

[0002] The mixed rare earth concentrate obtained through beneficiation mainly includes bastnaesite and monazite. Due to the complexity of the concentrate composition, it is a recognized difficult smelting ore.

[0003] At present, the main mixed rare earth concentrate decomposition technologies for industrialization include concentrated sulfuric acid high-temperature roasting decomposition process and concentrated alkali solution atmospheric decomposition process. The concentrated sulfuric acid high-temperature roasting decomposition process is to mix the rare earth concentrate with concentrated sulfuric acid and roast at 500-800℃. In the reaction process, when the mineral particles are too large, it will lead to incomplete internal reaction and affect the rare earth decomposition rate. In addition, this process produces a large amount of high-temperature mixed acid tail gas (SO2, SO3, H2SO4, HF, SiF4), transformation sulfate wastewater and radioactive waste residue, which are difficult to handle, resulting in a large environmental protection treatment engineering system and high cost. The concentrated alkali solution decomposition process treats mixed rare earth concentrate with REO grade of about 60%, and produces a large amount of mixed alkali wastewater (NaOH, Na3PO4, NaF, Na2CO3, Na2SO4 and NaCl) by decomposing rare earth minerals with sodium hydroxide. The resource recovery is difficult, resulting in excessive waste of sodium hydroxide, which can only be simply neutralized and discharged after reaching the standard, and cannot recover fluorine, phosphorus and other resources.

[0004] CN106591607A discloses a liquid alkali decomposition method for high-grade mixed rare earth concentrate, which comprises: mixing high-grade mixed rare earth concentrate with REO greater than 60wt% with sodium hydroxide solution with a concentration of >60wt%, the weight ratio of mixed rare earth concentrate to sodium hydroxide being 1:3.5-7.5, and the mixed slurry being reacted at 150-160℃ for 0.2-1 hour; after the reaction is completed, hot filtration is carried out at a temperature greater than 60℃, and the alkali cake obtained by filtration is washed to neutral; the alkali cake washed to neutral is dissolved with 6-10mol / L hydrochloric acid, the pH is controlled at 4-5, and a pure rare earth chloride solution is obtained.

[0005] CN106978531A discloses a method for decomposing mixed rare earth concentrate by acid-base combination, which comprises the following steps: mixing the mixed rare earth concentrate with concentrated sulfuric acid with mass percentage of > 92wt%, and calcining the mixture at 120-180℃ for 150-300min; after neutralization of the water leaching solution, phosphorus-iron-thorium slag and rare earth sulfate solution are formed; the water leaching residue is separated by gravity separation to obtain calcium sulfate waste residue and phosphorus-containing minerals; the phosphorus-containing minerals and the phosphorus-iron-thorium slag are decomposed with sodium hydroxide solution with mass percentage of 45wt%-70wt% at 130-180℃, and the rare earth chloride is obtained by dissolving in hydrochloric acid. The method separates calcium sulfate and phosphorus-containing minerals by gravity separation, but the separation effect is poor due to the conventional beneficiation method, resulting in low rare earth yield.

[0006] CN112534072A discloses a smelting separation process for treating rare earth concentrate by combined method, which adopts the method of atmosphere roasting-hydrochloric acid leaching-sulfuric acid roasting to treat the rare earth concentrate containing bastnaesite, and controls the low concentration hydrochloric acid step-by-step leaching in the hydrochloric acid leaching process to obtain high concentration rare earth solution, so that the leaching rate of Ce reaches more than 60%, and the F content of the leaching solution is reduced by aging. The leaching residue is further recovered by sulfuric acid roasting-water leaching to obtain the total rare earth yield of more than 95%. The process cannot recover calcium and phosphorus alone. The total rare earth yield still needs to be further improved. -

[0007] CN114959319A discloses a processing method of solid material obtained by alkali decomposition process of mixed rare earth concentrate, which comprises the following steps: 1) the mixed rare earth concentrate is sequentially subjected to caustic soda decomposition, water washing of alkali cake and hydrochloric acid optimization, to obtain chlorinated rare earth solution and optimization solid material; the chlorinated rare earth solution is neutralized by alkali reagent to remove impurities, to obtain neutralized chlorinated rare earth solution and neutralized solid material; the mixture of the neutralized solid material and the optimization solid material is subjected to the above-mentioned caustic soda decomposition, water washing of alkali cake and hydrochloric acid optimization steps for more than twice, to obtain the solid material to be treated; 2) the solid material to be treated is washed with hydrochloric acid solution for N times, N is a natural number of 3-9; the HCl concentration in the hydrochloric acid solution is 2.5-4.0mol / L; the washing temperature is 50-70℃; 3) water washing is adopted to obtain discharge solid material. The process cannot recover fluorine, phosphorus and calcium alone. SUMMARY

[0008] Therefore, the purpose of the present application is to provide a method for decomposing mixed rare earth concentrate and comprehensively utilizing associated resources, which can recover rare earth, fluorine, phosphorus and calcium resources respectively, and obtain chlorinated rare earth solution, sodium fluoride, trisodium phosphate and calcium chloride solution respectively.

[0009] The present application achieves the above-mentioned purposes by the following technical solutions. ​

[0010] The application provides a method for decomposing mixed rare earth concentrate and comprehensively utilizing associated resources, comprising the following steps:

[0011] 1) reacting the mixed rare earth concentrate with hydrochloric acid solution A to obtain rough selected mineral and mother liquor;

[0012] 2) reacting the rough selected mineral with hydrochloric acid solution B to obtain re-decomposed mineral and first acid solution containing chlorinated rare earth; wherein the concentration of the hydrochloric acid solution B is greater than that of the hydrochloric acid solution A;

[0013] 3) reacting the re-decomposed mineral with alkali solution C, and then performing solid-liquid separation to obtain first filter cake and first filtrate; washing the first filter cake to obtain first alkali cake and first washing alkali solution; recovering fluorinated salt from the first washing alkali solution; reacting the first alkali cake with a solution containing hydrochloric acid to obtain first acid residue and second acid solution containing chlorinated rare earth; wherein the alkali solution C is at least one selected from alkali metal carbonate solution and alkali metal hydroxide solution;

[0014] 4) reacting the first acid residue with alkali solution D, and then performing solid-liquid separation to obtain second filter cake and second filtrate; washing the second filter cake to obtain second alkali cake and second washing alkali solution; recovering phosphated salt from the second washing alkali solution; reacting the second alkali cake with a solution containing hydrochloric acid to obtain second acid residue and third acid solution containing chlorinated rare earth; wherein the alkali solution D is alkali metal hydroxide solution; and the alkalinity of the alkali solution D is greater than that of the alkali solution C.

[0015] The application further provides a method for decomposing mixed rare earth concentrate and comprehensively utilizing associated resources, comprising the following steps:

[0016] 1) reacting the mixed rare earth concentrate with hydrochloric acid solution A to obtain rough selected mineral and mother liquor;

[0017] 2) reacting the rough selected mineral with hydrochloric acid solution B to obtain re-decomposed mineral and first acid solution containing chlorinated rare earth; wherein the concentration of the hydrochloric acid solution B is greater than that of the hydrochloric acid solution A;

[0018] 3) reacting the re-decomposed mineral with alkali solution C, and then performing solid-liquid separation to obtain first filter cake and first filtrate; washing the first filter cake to obtain first alkali cake and first washing alkali solution; recovering fluorinated salt from the first washing alkali solution; wherein the alkali solution C is at least one selected from alkali metal carbonate solution and alkali metal hydroxide solution;

[0019] 4) reacting the first alkali cake with alkali solution D, and then performing solid-liquid separation to obtain third filter cake and third filtrate; washing the third filter cake to obtain third alkali cake and third washing alkali solution; recovering phosphated salt from the third washing alkali solution; reacting the third alkali cake with a solution containing hydrochloric acid to obtain third acid residue and fourth acid solution containing chlorinated rare earth; wherein the alkali solution D is alkali metal hydroxide solution; and the alkalinity of the alkali solution D is greater than that of the alkali solution C.

[0020] According to the method, preferably, in step 1), the concentration of the hydrochloric acid solution A is 2-4 mol / L; the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg: 0.8-4 L; the reaction temperature is 65-95 DEG C, and the reaction time is 0.5-6.5 h.

[0021] According to the method, preferably, in step 1), the following step is further included: the mother liquor is neutralized to a pH value of 6.5-7 with a calcium-containing inorganic substance to obtain a calcium chloride solution and a rare earth phosphate solid; wherein the calcium-containing inorganic substance is calcium oxide or calcium hydroxide.

[0022] According to the method, preferably, in step 2), the concentration of the hydrochloric acid solution B is 7-12 mol / L; the mass of the roughing mineral to the volume of the hydrochloric acid solution B is 1 kg: 1-3 L; the reaction temperature is 80-110 DEG C, and the reaction time is 0.5-4 h.

[0023] According to the method, preferably, in step 1), during the reaction of the mixed rare earth concentrate and the hydrochloric acid solution A, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid; in step 2), during the reaction of the roughing mineral and the hydrochloric acid solution B, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid.

[0024] In step 3), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2), and the mixed acid of hydrochloric acid and hydrofluoric acid; in step 4), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2), the second acid solution containing chlorinated rare earth obtained in step 3), and the mixed acid of hydrochloric acid and hydrofluoric acid.

[0025] According to the method, preferably, in step 3), the concentration of the lye C is 10-50 wt%; the mass of the re-decomposition mineral to the volume of the lye C is 1 kg: 1-3 L; the reaction temperature is 100-135 DEG C, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-5 h.

[0026] According to the method, preferably, in step 1), during the reaction of the mixed rare earth concentrate and the hydrochloric acid solution A, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid; in step 2), during the reaction of the roughing mineral and the hydrochloric acid solution B, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid.

[0027] In step 4), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2), the second acid solution containing chlorinated rare earth obtained in step 3), and a mixed acid of the hydrochloric acid and hydrofluoric acid.

[0028] According to the method of the present application, preferably, step 4) comprises the following specific steps: reacting the first acid residue, the rare earth phosphate solid with the alkali solution D; wherein the ratio of the sum of the mass of the first acid residue and the rare earth phosphate solid to the volume of the alkali solution D is 1 kg: 1-2.5 L.

[0029] According to the method of the present application, preferably, step 4) comprises the following specific steps: reacting the first acid residue, the rare earth phosphate solid with the alkali solution D; wherein the ratio of the sum of the mass of the first acid residue and the rare earth phosphate solid to the volume of the alkali solution D is 1 kg: 1-2.5 L.

[0030] According to the method of the present application, preferably, in step 4), the concentration of the alkali solution D is 40-65 wt%, the reaction temperature is 140-180℃, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-4.5 h.

[0031] The method of the present application can recover rare earth, fluorine, phosphorus and calcium separately by using low-concentration hydrochloric acid solution A, high-concentration hydrochloric acid solution B, low-concentration alkali solution C and high-concentration alkali solution D to stepwise and directional decompose the mixed rare earth concentrate, thereby obtaining chlorinated rare earth solution, sodium fluoride, trisodium phosphate and calcium chloride solution. The process conditions of the method are mild, which is conducive to industrial application. Moreover, the method basically has no wastewater discharge, and is green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The flowcharts of embodiments 1, 2 and 3 of the present application are shown. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited thereto.

[0034] In the prior art, although there are documents reporting that the mixed rare earth concentrate is first treated with low-concentration hydrochloric acid, but it is directly decomposed by alkali method after the treatment, which cannot achieve the technical effects of the present application. The method for decomposing the mixed rare earth concentrate and comprehensively utilizing the associated resources of the present application does not belong to the conventional selection.

[0035] The method for decomposing the mixed rare earth concentrate and comprehensively utilizing the associated resources of the present application comprises the following steps: (1) reacting with hydrochloric acid solution A; (2) reacting with hydrochloric acid solution B; (3) reacting with alkali solution C; and (4) reacting with alkali solution D. Optionally, it also comprises a purification step of the acid solution containing chlorinated rare earth. The following will be described in detail.

[0036] <Reaction with hydrochloric acid solution A>

[0037] The mixed rare earth concentrate is reacted with the hydrochloric acid solution A to obtain a roughed mineral and a mother liquor. This is advantageous for preferentially decomposing calcium-containing minerals and not substantially decomposing other minerals.

[0038] In the present application, the mixed rare earth concentrate is mainly composed of bastnaesite and monazite minerals, and also contains apatite, fluorite and the like. The mass ratio of bastnaesite to monazite is greater than or equal to 2:1. In the mixed rare earth concentrate of the present application, the REO content is greater than or equal to 40wt%, the fluorine (F) content is 4-10wt%, the phosphorus (P) content is 3-7wt%, and the CaO content is less than or equal to 15wt%.

[0039] According to one embodiment of the present application, in the mixed rare earth concentrate, the REO content is 42.3-51.4wt%, the fluorine (F) content is 4.6-8.2wt%, the phosphorus (P) content is 3.8-4.3wt%, and the CaO content is 9.7-13.6wt%.

[0040] According to another embodiment of the present application, in the mixed rare earth concentrate, the REO content is 55-65wt% (for example, 55wt%, 58wt%, 60.8wt%, 65wt%), the fluorine (F) content is 8.5-9.5wt%, the phosphorus (P) content is 4.5-6.2wt%, and the CaO content is less than or equal to 5wt% (for example, 4.3wt%).

[0041] In the present application, the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1kg:0.8-4L, for example, it can be 1kg:0.8L, 1kg:1L, 1kg:1.5L, 1kg:2L, 1kg:2.5L, 1kg:3L, 1kg:3.5L, 1kg:4L. The concentration of the hydrochloric acid solution A can be 2-4mol / L, preferably 2.5-3.5mol / L, for example, it can be 2.5mol / L, 3mol / L, 3.5mol / L. The reaction temperature of the mixed rare earth concentrate with the hydrochloric acid solution A can be 65-95℃, for example, it can be 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃. The reaction time can be 0.5-6.5h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h. This is advantageous for dissolving calcium elements and reducing the dissolution of rare earths, thereby obtaining a calcium chloride solution with a relatively high calcium chloride content.

[0042] In the reaction process of the mixed rare earth concentrate and the hydrochloric acid solution A, the mixed acid of hydrochloric acid and hydrofluoric acid can be obtained by spraying and absorbing the tail gas. The mixed acid can be used to react with the first or second alkali cake obtained in the following steps.

[0043] In the present application, the mother liquor is neutralized with the calcium-containing inorganic substance to obtain the calcium chloride solution and the rare earth phosphate solid. Specifically, the mother liquor is neutralized with the calcium-containing inorganic substance to a pH value of 6.5-7, preferably to a pH value of 7. The calcium-containing inorganic substance is calcium oxide or calcium hydroxide, preferably calcium oxide. The concentration of the obtained calcium chloride solution is greater than or equal to 55 g / L, preferably greater than or equal to 58 g / L, more preferably greater than or equal to 60 g / L. The rare earth phosphate solid is the rare earth substance mainly combined with phosphate, which can be used to react with the alkali liquor D to obtain the decomposition.

[0044] In the present application, the roughed mineral is the mineral obtained after removing the calcium-containing mineral, including the rare earth mineral combined with carbonate, the rare earth mineral combined with fluoride, the rare earth mineral combined with phosphate, etc.

[0045] According to one specific embodiment of the present application, the mixed rare earth concentrate is reacted with the hydrochloric acid solution A to obtain the roughed mineral and the mother liquor by solid-liquid separation; the mother liquor is neutralized with the calcium-containing inorganic substance to obtain the calcium chloride solution and the rare earth phosphate solid by solid-liquid separation. In the present application, the solid-liquid separation can be filtration or centrifugation, preferably filtration.

[0046] <Reaction with the hydrochloric acid solution B>

[0047] The roughed mineral obtained above is reacted with the hydrochloric acid solution B to obtain the re-decomposed mineral and the first acid solution containing chlorinated rare earth; wherein the concentration of the hydrochloric acid solution B is greater than that of the hydrochloric acid solution A. This is beneficial to decompose the rare earth mineral combined with carbonate to obtain the first acid solution containing chlorinated rare earth.

[0048] In the present application, the mass of the roughed mineral to the volume of the hydrochloric acid solution B can be 1 kg: 1-3 L, for example, 1 kg: 1 L, 1 kg: 2 L, 1 kg: 3 L. The concentration of the hydrochloric acid solution B can be 7-12 mol / L, preferably 8-12 mol / L, for example, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L. The reaction temperature of the roughed mineral with the hydrochloric acid solution B can be 80-110°C, preferably 80-100°C, for example, 80°C, 90°C, 100°C. The reaction time can be 0.5-4 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h. In this step, the mass of the roughed mineral refers to the dry weight of the roughed mineral. This is beneficial to control the decomposition of the rare earth mineral combined with carbonate in the roughed mineral, and not to decompose the rare earth mineral combined with fluoride and the rare earth mineral combined with phosphate.

[0049] In the reaction process of the rough selected mineral and the hydrochloric acid solution B, the mixed acid of hydrochloric acid and hydrofluoric acid is obtained by spraying and absorbing the tail gas. The mixed acid can be used to react with the first or second alkali cake obtained in the later step.

[0050] According to one embodiment of the present application, the rough selected mineral obtained as above is reacted with the hydrochloric acid solution B, and solid-liquid separation is performed to obtain a re-decomposed mineral and a first acid solution containing chlorinated rare earth. In the present application, the solid-liquid separation can be filtration or centrifugation, and is preferably filtration.

[0051] <Reaction with alkali liquor C>

[0052] In some embodiments, the re-decomposed mineral is reacted with the alkali liquor C, and solid-liquid separation is performed to obtain a first filter cake and a first filtrate; the first filter cake is washed to obtain a first alkali cake and a first washing alkali liquor; the first washing alkali liquor is recovered for fluorinated salt; the first alkali cake is reacted with a solution containing hydrochloric acid to obtain a first acid residue and a second acid solution containing chlorinated rare earth; wherein the alkali liquor C is selected from at least one of an alkali metal carbonate solution and an alkali metal hydroxide solution.

[0053] In other embodiments, the re-decomposed mineral is reacted with the alkali liquor C, and solid-liquid separation is performed to obtain a first filter cake and a first filtrate; the first filter cake is washed to obtain a first alkali cake and a first washing alkali liquor; the first washing alkali liquor is recovered for fluorinated salt; and the first alkali cake is not reacted with a solution containing hydrochloric acid (but is directly used to react with alkali liquor D, which will be described in detail below). Wherein the alkali liquor C is selected from at least one of an alkali metal carbonate solution and an alkali metal hydroxide solution. In this way, the rare earth mineral mainly combined with fluoride ions is decomposed, and the rare earth mineral combined with phosphate ions is not decomposed.

[0054] In the present application, the ratio of the mass of the re-dissolved mineral to the volume of the alkali solution C can be 1 kg: 1-3 L, for example, it can be 1 kg: 1 L, 1 kg: 2 L, 1 kg: 3 L. In this step, the mass of the re-dissolved mineral refers to the dry weight of the re-dissolved mineral. The concentration of the alkali solution C can be 10-50 wt%. The alkali solution C is selected from at least one of an alkali metal carbonate solution, an alkali metal hydroxide solution. The alkali metal is selected from one of sodium element, potassium element, preferably sodium element. In some embodiments, the alkali solution C is an alkali metal carbonate solution, and the concentration thereof is 30-50 wt%. In other embodiments, the alkali solution C is a sodium hydroxide solution, and the concentration thereof is 10-30 wt%. In still other embodiments, the alkali solution C is a mixed solution containing sodium carbonate and sodium hydroxide, wherein the concentration of sodium carbonate is 30-40 wt%, and the concentration of sodium hydroxide is 5-20 wt%, for example, the concentration of sodium hydroxide is 5 wt%, 10 wt%, 15 wt%, 20 wt%. The reaction temperature of the re-dissolved mineral and the alkali solution C can be 100-135 °C, for example, it can be 100 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C. The reaction pressure can be 0.1-1 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa. The reaction time can be 0.5-5 h, preferably 0.5-4 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h. This is beneficial for completely decomposing the rare earth mineral combined with fluoride ions.

[0055] In the present application, the first alkali washing solution can be used to recover the fluoride salt and the first residual alkali by means of concentration and crystallization. According to one specific embodiment of the present application, the alkali solution C is selected from at least one of a sodium carbonate solution, a sodium hydroxide solution; the first alkali washing solution can be used to recover sodium fluoride and the first residual alkali by means of concentration and crystallization. The purity of the sodium fluoride is ≥ 94 wt%, up to 94.6 wt%. The first residual alkali and the first filtrate can be mixed and then supplemented with sodium hydroxide to prepare the alkali solution C required for the reaction in this step.

[0056] In the present application, the first alkali cake is reacted with a solution containing hydrochloric acid, and solid-liquid separation is performed to obtain a first acid residue and a second acid solution containing chlorinated rare earth; wherein the solution containing hydrochloric acid is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained above, the mixed acid of hydrochloric acid and hydrofluoric acid obtained above. The solid-liquid separation can be centrifugation or filtration. Preferably, it is filtration.

[0057] In some embodiments, the first alkali cake is reacted with the first acid solution containing chlorinated rare earth, filtered and washed to obtain a first acid residue and a second acid solution containing chlorinated rare earth.

[0058] In some embodiments, the first acid residue is dissolved with a freshly prepared hydrochloric acid solution, filtered and washed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0059] In some embodiments, the first acid residue is dissolved with a freshly prepared hydrochloric acid solution, filtered and washed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0060] <Reaction with alkali solution D>

[0061] Reaction of the first acid-soluble residue with the alkaline solution D and reaction of the first acid-soluble residue, the rare earth phosphate solids with the alkaline solution D

[0062] In some embodiments, the first acid residue is dissolved with a freshly prepared hydrochloric acid solution, filtered and washed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0063] According to an embodiment of the present application, the first acid residue, the rare earth phosphate solid obtained above, is reacted with an alkali solution D, solid-liquid separation is performed to obtain a second filter cake and a second filtrate; the second filter cake is washed to obtain a second alkali cake and a second washed alkali solution; the second washed alkali solution is recovered for phosphate; the second alkali cake is reacted with a solution containing hydrochloric acid to obtain a second acid residue and a third acid solution containing rare earth chlorides; wherein the alkali solution D is an alkali metal hydroxide solution; the alkali solution D has a higher alkalinity than the alkali solution C. This is advantageous for the decomposition of the rare earth ore combined with phosphate (i.e. for the decomposition of monazite ore), and is advantageous for obtaining a higher-purity trisodium phosphate.

[0064] The ratio of the sum of the mass of the first acid residue and the solid rare earth phosphate to the volume of the alkali solution D can be 1 kg:1-2.5 L, for example, 1 kg:1 L, 1 kg:1.5 L, 1 kg:1.8 L, 1 kg:2 L, 1 kg:2.5 L. The concentration of the alkali solution D can be 40-65 wt%, for example, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%. The alkali solution D is an alkali metal hydroxide solution, which can be specifically a sodium hydroxide solution or a potassium hydroxide solution, and is preferably a sodium hydroxide solution. The reaction temperature of the first acid residue and the alkali solution D can be 140-180°C, for example, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C. The reaction pressure can be 0.1-1 MPa, for example, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa. The reaction time can be 0.5-4.5 h, preferably 0.5-4 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h. In this way, the decomposition of the rare earth mineral combined with phosphate can be achieved, and a trisodium phosphate with high purity can be obtained.

[0065] According to one embodiment of the present application, the alkali solution D used is a sodium hydroxide solution, the second alkali solution is recovered by cooling crystallization to obtain trisodium phosphate, and a second residual alkali is obtained. The trisodium phosphate is trisodium phosphate dodecahydrate, and the purity is ≥98 wt%, which can reach 98.7 wt%.

[0066] In the present application, the second filtrate and the second residual alkali can be mixed to form the alkali solution D of 40-65 wt% by adding an alkali metal hydroxide, which is used for the reaction of this step.

[0067] In the present application, the solution containing hydrochloric acid is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing rare earth chloride obtained above, the second acid solution containing rare earth chloride obtained above, the mixed acid of hydrochloric acid and hydrofluoric acid obtained above. In the present application, it also includes: at least removing impurities from the obtained third acid solution containing rare earth chloride to obtain a purified rare earth chloride solution.

[0068] In some specific embodiments, the second alkali cake is reacted with the obtained second acid solution containing rare earth chloride, and solid-liquid separation is performed to obtain a second acid residue and a third acid solution containing rare earth chloride; the obtained third acid solution containing rare earth chloride is adjusted in solution concentration and then neutralized to remove impurities to obtain a purified rare earth chloride solution. In the present application, the concentration of the third acid solution containing rare earth chloride can be adjusted to the required range by adding water.

[0069] In some specific embodiments, the second alkali cake is reacted with the first acid solution containing chlorinated rare earth, solid-liquid separation is performed to obtain a second acid residue and a third acid solution containing chlorinated rare earth; the second acid solution containing chlorinated rare earth and the third acid solution containing chlorinated rare earth are mixed, and after adjusting the concentration of the solution, impurities are removed by neutralization to obtain a purified chlorinated rare earth solution.

[0070] In some specific embodiments, the second alkali cake is reacted with directly prepared hydrochloric acid, solid-liquid separation is performed to obtain a second acid residue and a third acid solution containing chlorinated rare earth; the first acid solution containing chlorinated rare earth, the second acid solution containing chlorinated rare earth, and the third acid solution containing chlorinated rare earth are mixed, and after adjusting the concentration of the solution, impurities are removed by neutralization to obtain a purified chlorinated rare earth solution.

[0071] Compared with the process of directly decomposing mixed rare earth concentrate by an alkali method, the method of the present application does not produce complex alkali wastewater, and the second filtrate and the second residual alkali can be recycled, and the first filtrate and the first residual alkali can be recycled.

[0072] Reaction of the first alkaline cake with the alkaline solution D and reaction of the first alkaline cake, the rare earth phosphate solids with the alkaline solution D

[0073] In some embodiments, the first alkali cake is reacted with alkali liquor D, solid-liquid separation is performed to obtain a third filter cake and a third filtrate; the third filter cake is washed to obtain a third alkali cake and a third washing alkali liquor; the third washing alkali liquor is recovered for phosphates; the third alkali cake is reacted with a solution containing hydrochloric acid to obtain a third acid residue and a fourth acid solution containing chlorinated rare earth; wherein the alkali liquor D is an alkali metal hydroxide solution; the alkalinity of the alkali liquor D is greater than the alkalinity of the alkali liquor C.

[0074] According to one embodiment of the present application, the first alkali cake, the rare earth phosphate solid, and alkali liquor D are reacted, solid-liquid separation is performed to obtain a third filter cake and a third filtrate; the third filter cake is washed to obtain a third alkali cake and a third washing alkali liquor; the third washing alkali liquor is recovered for phosphates; the third alkali cake is reacted with a solution containing hydrochloric acid to obtain a third acid residue and a fourth acid solution containing chlorinated rare earth; wherein the alkali liquor D is an alkali metal hydroxide solution; the alkalinity of the alkali liquor D is greater than the alkalinity of the alkali liquor C.

[0075] In the present application, the ratio of the sum of the mass of the first alkali cake and the solid of the rare earth phosphate to the volume of the alkali liquor D can be 1 kg:1-2.5 L, for example, can be 1 kg:1 L, 1 kg:1.5 L, 1 kg:1.8 L, 1 kg:2 L, 1 kg:2.5 L. The concentration of the alkali liquor D can be 40-65 wt%, for example, can be 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%. The alkali liquor D is an alkali metal hydroxide solution, specifically can be a sodium hydroxide solution or a potassium hydroxide solution, preferably a sodium hydroxide solution. The reaction temperature of the first alkali cake, the solid of the rare earth phosphate and the alkali liquor D can be 140-180℃, for example, can be 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃. The reaction pressure can be 0.1-1 MPa, for example, can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa. The reaction time can be 0.5-4.5 h, preferably 0.5-4 h, for example, can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h. In this way, the first alkali cake, the solid of the rare earth phosphate is better decomposed.

[0076] When the alkali liquor D is a sodium hydroxide solution, the third alkali washing liquor is recovered into trisodium phosphate with a purity of ≥98 wt%, which can reach 98.6 wt%. The solution containing hydrochloric acid is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing rare earth chlorides obtained as above, and mixed acid of the hydrochloric acid and hydrofluoric acid.

[0077] <Analysis method>

[0078] REO content: analyzed by gravimetric method.

[0079] P content: analyzed by phosphorus bismuth molybdenum blue spectrophotometry.

[0080] F content: analyzed by distillation method.

[0081] CaO content: analyzed by EDTA titration method.

[0082] Purity of trisodium phosphate: determined by the method of HGT2517-2009 Industrial Trisodium Phosphate Standard.

[0083] Concentration of calcium chloride solution: the calcium content in the solution is determined by gravimetric method, and the concentration of calcium chloride is calculated.

[0084] Purity of sodium fluoride: determined by the method of YS / T 517-2024 Sodium Fluoride Standard.

[0085] The flowchart of the following Examples 1, 2 and 3 is referred toFigure 1 The results are shown in Table 1.

[0086] Example 1

[0087] The mixed rare earth concentrate of the present embodiment has a REO content of 42.3wt%, a fluorine content of 4.6wt%, a phosphorus content of 3.8wt%, and a CaO content of 13.6wt%.

[0088] 1) The mixed rare earth concentrate was mixed with hydrochloric acid solution A having a concentration of 2.5mol / L (the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A was 1kg:4L), and reacted at 70°C for 4h. During the reaction, the tail gas was absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction, filtration was performed to obtain a roughing mineral and a mother liquor. The mother liquor was neutralized to a pH value of 7 with calcium oxide, and filtration was performed to obtain a calcium chloride solution and a rare earth phosphate solid.

[0089] 2) The roughing mineral obtained above was mixed with hydrochloric acid solution B having a concentration of 8mol / L (the mass of the roughing mineral to the volume of the hydrochloric acid solution B was 1kg:3L), and reacted at 100°C for 0.5h. During the reaction, the tail gas was absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction, filtration was performed to obtain a re-decomposition mineral and a first acid solution containing rare earth chlorides.

[0090] 3) The re-decomposition mineral obtained above was mixed with a sodium hydroxide solution having a concentration of 10wt% (i.e., lye C, the mass of the re-decomposition mineral to the volume of the lye C was 1kg:3L), and reacted at a temperature of 100°C and a pressure of 0.1MPa for 4h. After the reaction, filtration was performed to obtain a first filter cake and a first filtrate. The first filter cake was washed with water to obtain a first lye cake and a first lye washing solution. The first lye washing solution was used to recover sodium fluoride and a first residual lye by means of concentration and crystallization. The first residual lye and the first filtrate were mixed and then used to prepare the lye C required for the reaction of the present step by supplementing sodium hydroxide. The first lye cake was dissolved in the first acid solution containing rare earth chlorides, and filtration and washing were performed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0091] 4) The first acid-soluble residue obtained above, the rare earth phosphate solid, and a sodium hydroxide solution having a concentration of 40 wt% (i.e., lye D, the ratio of the sum of the mass of the first acid-soluble residue and the rare earth phosphate solid to the volume of lye D is 1 kg:2.5 L) are mixed, and reacted at a temperature of 140°C and a pressure of 0.1 MPa for 4 h. After the reaction is completed, filtration is performed to obtain a second filter cake and a second filtrate. The second filter cake is washed with water to obtain a second lye cake and a second lye washing liquid. The second lye washing liquid is cooled and crystallized to recover trisodium phosphate and a second residual lye. The second residual lye and the second filtrate are mixed and then used to prepare lye D required for the reaction of this step by supplementing sodium hydroxide. The second lye cake is dissolved with a second acid solution containing rare earth chlorides, filtered and washed to obtain a second acid-soluble residue and a third acid solution containing rare earth chlorides. The third acid solution containing rare earth chlorides is adjusted in solution concentration by adding water and impurities are removed by neutralization to obtain a purified rare earth chloride solution.

[0092] Example 2

[0093] The mixed rare earth concentrate of this example has a REO content of 51.4 wt%, a fluorine content of 8.2 wt%, a phosphorus content of 4.3 wt%, and a CaO content of 9.7 wt%.

[0094] 1) The mixed rare earth concentrate is mixed with hydrochloric acid solution A having a concentration of 3 mol / L (the ratio of the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg:1.5 L), and reacted at 90°C for 2 h. During the reaction, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction is completed, filtration is performed to obtain a rough separation mineral and a mother liquor. The mother liquor is neutralized to a pH value of 7 with calcium oxide to obtain a calcium chloride solution and a rare earth phosphate solid.

[0095] 2) The rough separation mineral obtained above is mixed with hydrochloric acid solution B having a concentration of 10 mol / L (the ratio of the mass of the rough separation mineral to the volume of the hydrochloric acid solution B is 1 kg:2 L), and reacted at 90°C for 2 h. During the reaction, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction is completed, filtration is performed to obtain a re-decomposition mineral and a first acid solution containing rare earth chlorides.

[0096] 3) The re-decomposition mineral obtained above is mixed with a sodium carbonate solution with a concentration of 30wt% (i.e. lye C, the ratio of the mass of the re-decomposition mineral to the volume of lye C is 1 kg:2 L), and is reacted at a temperature of 110°C and a pressure of 0.3 MPa for 2 h. After the reaction is completed, filtration is performed to obtain a first filter cake and a first filtrate. The first filter cake is washed with water to obtain a first lye cake and a first lye washing solution. The first lye washing solution is used to recover sodium fluoride and a first residual lye by means of concentrated crystallization. The first residual lye and the first filtrate are mixed and then used to prepare lye C required for the reaction of this step by supplementing sodium carbonate. The first lye cake is dissolved in the mixed acid of hydrochloric acid and hydrofluoric acid obtained in steps 1) and 2), filtered and washed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0097] 4) The first acid residue obtained above, the rare earth phosphate solid, and a sodium hydroxide solution with a concentration of 50wt% (i.e. lye D, the ratio of the sum of the mass of the first acid residue and the rare earth phosphate solid to the volume of lye D is 1 kg:1.8 L) are mixed, and are reacted at a temperature of 160°C and a pressure of 0.5 MPa for 3 h. After the reaction is completed, filtration is performed to obtain a second filter cake and a second filtrate. The second filter cake is washed with water to obtain a second lye cake and a second lye washing solution. The second lye washing solution is used to recover trisodium phosphate and a second residual lye by means of cooling crystallization. The second residual lye and the second filtrate can be used to prepare lye D required for the reaction of this step by supplementing sodium hydroxide. The second lye cake is dissolved in the first acid solution containing rare earth chlorides, filtered and washed to obtain a second acid residue and a third acid solution containing rare earth chlorides. The second acid solution containing rare earth chlorides and the third acid solution containing rare earth chlorides are mixed, and the solution concentration is adjusted by adding water, impurities are removed by neutralization to obtain a purified rare earth chloride solution.

[0098] Example 3

[0099] In the mixed rare earth concentrate of this example, the REO content is 60.8wt%, the fluorine content is 9.5wt%, the phosphorus content is 6.2wt%, and the CaO content is 4.3wt%.

[0100] 1) The mixed rare earth concentrate is mixed with a hydrochloric acid solution A with a concentration of 3.5 mol / L (the ratio of the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg:0.8 L), and is reacted at 95°C for 0.5 h. During the reaction, tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction is completed, filtration is performed to obtain a roughed mineral and a mother liquor. The mother liquor is neutralized to a pH value of 7 with calcium oxide, and filtration is performed to obtain a calcium chloride solution and a rare earth phosphate solid.

[0101] 2) The crude ore concentrate obtained above is mixed with hydrochloric acid solution B (the ratio of the mass of the crude ore concentrate to the volume of the hydrochloric acid solution B is 1 kg: 1 L) with a concentration of 12 mol / L, and reacted at 80°C for 4 h. During the reaction, the tail gas is absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction, filtration is performed to obtain a re-decomposition mineral and a first acid solution containing rare earth chlorides.

[0102] 3) The re-decomposition mineral obtained above is mixed with a mixed solution containing sodium carbonate and sodium hydroxide (the mixed solution is alkali liquor C, wherein the concentration of sodium carbonate is 30 wt%, and the concentration of sodium hydroxide is 20 wt%; the ratio of the mass of the re-decomposition mineral to the volume of the mixed solution is 1 kg: 1 L), and reacted at a temperature of 115°C and a pressure of 1 MPa for 0.5 h. After the reaction, filtration is performed to obtain a first filter cake and a first filtrate. The first filter cake is washed with water to obtain a first alkali cake and a first washing alkali liquor. The first washing alkali liquor is used to recover sodium fluoride and a first residual alkali by concentration and crystallization. The first residual alkali and the first filtrate are mixed and used to prepare the alkali liquor C required for the reaction of this step by supplementing sodium carbonate and sodium hydroxide. The first alkali cake is dissolved with freshly prepared hydrochloric acid, filtered and washed to obtain a first acid residue and a second acid solution containing rare earth chlorides.

[0103] 4) The first acid residue, the rare earth phosphate solid obtained above, and a sodium hydroxide solution (i.e., alkali liquor D) with a concentration of 65 wt% are mixed (the ratio of the sum of the mass of the first acid residue and the rare earth phosphate solid to the volume of the alkali liquor D is 1 kg: 1 L), and reacted at a temperature of 180°C and a pressure of 1 MPa for 0.5 h. After the reaction, filtration is performed to obtain a second filter cake and a second filtrate. The second filter cake is washed with water to obtain a second alkali cake and a second washing alkali liquor. The second washing alkali liquor is cooled and crystallized to recover trisodium phosphate and a second residual alkali. The second residual alkali and the second filtrate are used to prepare the alkali liquor D required for the reaction of this step by supplementing sodium hydroxide. The second alkali cake is dissolved with freshly prepared hydrochloric acid, filtered and washed to obtain a second acid residue and a third acid solution containing rare earth chlorides. The first acid solution containing rare earth chlorides, the second acid solution containing rare earth chlorides, and the third acid solution containing rare earth chlorides are mixed, the concentration of the solution is adjusted by adding water, impurities are removed by neutralization, and a purified rare earth chloride solution is obtained.

[0104] Example 4

[0105] In the mixed rare earth concentrate of this embodiment, the content of REO is 51.4 wt%, the content of fluorine is 8.2 wt%, the content of phosphorus is 4.3 wt%, and the content of CaO is 9.7 wt%.

[0106] 1) The mixed rare earth concentrate is mixed with hydrochloric acid solution A with a concentration of 3 mol / L (the ratio of the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg: 1 L), and reacted at 95°C for 1 h. The tail gas is absorbed by spraying during the reaction to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction, filtration is performed to obtain a rough selected mineral and a mother liquor. The mother liquor is neutralized to a pH value of 7 with calcium oxide to obtain a calcium chloride solution and a rare earth phosphate solid.

[0107] 2) The rough selected mineral obtained above is mixed with hydrochloric acid solution B with a concentration of 10 mol / L (the ratio of the mass of the rough selected mineral to the volume of the hydrochloric acid solution B is 1 kg: 1.5 L), and reacted at 95°C for 1 h. The tail gas is absorbed by spraying during the reaction to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. After the reaction, filtration is performed to obtain a re-decomposition mineral and a first acid solution containing rare earth chlorides.

[0108] 3) The re-decomposition mineral obtained above is mixed with a mixed solution containing sodium carbonate and sodium hydroxide (the mixed solution is alkali liquor C, wherein the concentration of sodium carbonate is 25 wt%, and the concentration of sodium hydroxide is 25 wt%; the ratio of the mass of the re-decomposition mineral to the volume of the mixed solution is 1 kg: 1.5 L), and reacted at a temperature of 135°C and a pressure of 0.8 MPa for 1.5 h. After the reaction, filtration is performed to obtain a first filter cake and a first filtrate. The first filter cake is washed with water to obtain a first alkali cake and a first washing alkali liquor. The first washing alkali liquor is used to recover sodium fluoride and a first residual alkali by concentration and crystallization. The first residual alkali and the first filtrate are mixed and then used to prepare the alkali liquor C required for the reaction of this step by supplementing sodium carbonate.

[0109] 4) The first alkali cake obtained above, the rare earth phosphate solid, and a sodium hydroxide solution with a concentration of 50 wt% (i.e. alkali liquor D; the ratio of the sum of the mass of the first alkali cake and the rare earth phosphate solid to the volume of the alkali liquor D is 1 kg: 1.8 L) are mixed, and reacted at a temperature of 160°C and a pressure of 0.5 MPa for 3 h. After the reaction, filtration is performed to obtain a third filter cake and a third filtrate. The third filter cake is washed with water to obtain a third alkali cake and a third washing alkali liquor. The third washing alkali liquor is cooled and crystallized to recover trisodium phosphate and a third residual alkali. The third residual alkali and the third filtrate can be used to prepare the alkali liquor D required for the reaction of this step by supplementing sodium hydroxide. The second alkali cake is dissolved in the first acid solution containing rare earth chlorides, filtered and washed to obtain a third acid residue and a fourth acid solution containing rare earth chlorides. The fourth acid solution containing rare earth chlorides obtained is adjusted in solution concentration by adding water, and impurities are removed by neutralization to obtain a purified rare earth chloride solution.

[0110] Table 1

[0111]

[0112] Note: In the table, M1 refers to the ratio of the mass of mixed rare earth concentrate to the volume of hydrochloric acid solution A; M2 refers to the ratio of the mass of roughing mineral to the volume of hydrochloric acid solution B; M3 refers to the ratio of the mass of re-decomposition mineral to the volume of alkali solution C; and M4 refers to the ratio of the sum of the mass of first acid solution residue and rare earth phosphate solid to the volume of alkali solution D.

[0113] Table 2

[0114]

[0115] Note: The calculation formula of total rare earth yield is:

[0116] Total rare earth yield (%) = weight of rare earth in purified rare earth chloride solution / weight of rare earth in mixed rare earth concentrate x 100%.

[0117] The present application is not limited to the above-mentioned embodiments, and any modification, improvement, or replacement conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.

Claims

1. A method for comprehensive utilization of mixed rare earth concentrate decomposition and associated resources, characterized in that, The method comprises the following steps: 1) reacting mixed rare earth concentrate with hydrochloric acid solution A to obtain roughing mineral and mother liquor; neutralizing the mother liquor with calcium-containing inorganic substance to pH 6.5-7 to obtain calcium chloride solution and rare earth phosphate solid; wherein the calcium-containing inorganic substance is calcium oxide or calcium hydroxide; wherein the concentration of the hydrochloric acid solution A is 2-4 mol / L; the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg: 0.8-4 L; the reaction temperature is 65-95℃, and the reaction time is 0.5-6.5 h; 2) reacting the roughing mineral with hydrochloric acid solution B to obtain re-decomposition mineral and first acid solution containing chlorinated rare earth; wherein the concentration of the hydrochloric acid solution B is greater than that of the hydrochloric acid solution A; the concentration of the hydrochloric acid solution B is 7-12 mol / L; the mass of the roughing mineral to the volume of the hydrochloric acid solution B is 1 kg: 1-3 L; the reaction temperature is 80-110℃, and the reaction time is 0.5-4 h; 3) reacting the re-decomposition mineral with alkali liquor C, and separating the solid and liquid to obtain first filter cake and first filtrate; washing the first filter cake to obtain first alkali cake and first washing alkali liquor; recovering fluorinated salt from the first washing alkali liquor; reacting the first alkali cake with hydrochloric acid-containing solution to obtain first acid residue and second acid solution containing chlorinated rare earth; wherein the mass of the re-decomposition mineral to the volume of the alkali liquor C is 1 kg: 1-3 L; the reaction temperature is 100-135℃, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-5 h; The alkali liquor C is selected from one of the following manners: (i) the alkali liquor C is alkali metal carbonate solution with a concentration of 30-50 wt%; the alkali metal is sodium element; (ii) the alkali liquor C is sodium hydroxide solution with a concentration of 10-30 wt%; (iii) the alkali liquor C is a mixed solution containing sodium carbonate and sodium hydroxide, wherein the concentration of sodium carbonate is 30-40 wt%, and the concentration of sodium hydroxide is 10-20 wt%; 4) reacting the first acid residue, the rare earth phosphate solid and alkali liquor D, and separating the solid and liquid to obtain second filter cake and second filtrate; washing the second filter cake to obtain second alkali cake and second washing alkali liquor; recovering phosphate salt from the second washing alkali liquor; reacting the second alkali cake with hydrochloric acid-containing solution to obtain second acid residue and third acid solution containing chlorinated rare earth; wherein the alkali liquor D is sodium hydroxide solution; the alkalinity of the alkali liquor D is greater than that of the alkali liquor C; the concentration of the alkali liquor D is 40-65 wt%; the reaction temperature is 140-180℃, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-4.5 h.

2. The method according to claim 1, characterized in that: in step 1), during the reaction of the mixed rare earth concentrate with the hydrochloric acid solution A, tail gas is absorbed by spraying to obtain mixed acid of hydrochloric acid and hydrofluoric acid; in step 2), during the reaction of the roughing mineral with the hydrochloric acid solution B, tail gas is absorbed by spraying to obtain mixed acid of hydrochloric acid and hydrofluoric acid. In step 3), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2, and a mixed acid of the hydrochloric acid and hydrofluoric acid; in step 4), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2, the second acid solution containing chlorinated rare earth obtained in step 3, and the mixed acid of the hydrochloric acid and hydrofluoric acid.

3. The method of claim 1, wherein, In step 4), the ratio of the sum of the mass of the first acid residue and the mass of the rare earth phosphate solid to the volume of the alkali solution D is 1 kg:1-2.5 L.

4. A method for comprehensive utilization of mixed rare earth concentrate decomposition and associated resources, characterized in that, The method comprises the following steps: 1) reacting the mixed rare earth concentrate with a hydrochloric acid solution A to obtain a roughed mineral and a mother liquor; neutralizing the mother liquor with a calcium-containing inorganic substance to a pH value of 6.5-7 to obtain a calcium chloride solution and a rare earth phosphate solid; wherein the calcium-containing inorganic substance is calcium oxide or calcium hydroxide; wherein the concentration of the hydrochloric acid solution A is 2-4 mol / L; the ratio of the mass of the mixed rare earth concentrate to the volume of the hydrochloric acid solution A is 1 kg:0.8-4 L; the reaction temperature is 65-95°C, and the reaction time is 0.5-6.5 h; 2) reacting the roughed mineral with a hydrochloric acid solution B to obtain a re-decomposed mineral and a first acid solution containing chlorinated rare earth; wherein the concentration of the hydrochloric acid solution B is greater than the concentration of the hydrochloric acid solution A; the concentration of the hydrochloric acid solution B is 7-12 mol / L; the ratio of the mass of the roughed mineral to the volume of the hydrochloric acid solution B is 1 kg:1-3 L; the reaction temperature is 80-110°C, and the reaction time is 0.5-4 h; 3) reacting the re-decomposed mineral with an alkali solution C, and then performing solid-liquid separation to obtain a first filter cake and a first filtrate; washing the first filter cake to obtain a first alkali cake and a first washing alkali solution; recovering fluorinated salt from the first washing alkali solution; wherein the ratio of the mass of the re-decomposed mineral to the volume of the alkali solution C is 1 kg:1-3 L; the reaction temperature is 100-135°C, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-5 h; The alkali solution C is selected from one of the following manners: (i) the alkali solution C is an alkali metal carbonate solution with a concentration of 30-50 wt%; the alkali metal is sodium element; (ii) the alkali solution C is a sodium hydroxide solution with a concentration of 10-30 wt%; (iii) the alkali solution C is a mixed solution containing sodium carbonate and sodium hydroxide, wherein the concentration of the sodium carbonate is 30-40 wt%, and the concentration of the sodium hydroxide is 10-20 wt%; 4) reacting the first alkali cake and the rare earth phosphate solid with an alkali solution D, and then performing solid-liquid separation to obtain a third filter cake and a third filtrate; washing the third filter cake to obtain a third alkali cake and a third washing alkali solution; recovering phosphate salt from the third washing alkali solution; reacting the third alkali cake with a hydrochloric acid-containing solution to obtain a third acid residue and a fourth acid solution containing chlorinated rare earth; wherein the alkali solution D is a sodium hydroxide solution; the alkalinity of the alkali solution D is greater than the alkalinity of the alkali solution C; the concentration of the alkali solution D is 40-65 wt%; the reaction temperature is 140-180°C, the reaction pressure is 0.1-1 MPa, and the reaction time is 0.5-4.5 h.

5. The method according to claim 1 or 4, characterized in that: In step 1), the concentration of the hydrochloric acid solution A is 2.5-3.5 mol / L; the reaction temperature is 70-95℃, and the reaction time is 0.5-4 h.

6. The method according to claim 1 or 4, characterized in that, In step 2), the concentration of the hydrochloric acid solution B is 8-12 mol / L.

7. The method of claim 4, wherein: In step 1), the mixed acid of hydrochloric acid and hydrofluoric acid is obtained by spraying and absorbing tail gas during the reaction of the mixed rare earth concentrate and the hydrochloric acid solution A; in step 2), the mixed acid of hydrochloric acid and hydrofluoric acid is obtained by spraying and absorbing tail gas during the reaction of the rough selected mineral and the hydrochloric acid solution B; In step 4), the hydrochloric acid-containing solution is selected from at least one of directly prepared hydrochloric acid, the first acid solution containing chlorinated rare earth obtained in step 2), and the mixed acid of hydrochloric acid and hydrofluoric acid.

8. The method of claim 4, wherein, In step 4), the ratio of the sum of the mass of the first alkali cake and the rare earth phosphate solid to the volume of the alkali liquor D is 1 kg: 1-2.5 L.

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