Processing method of mixed rare earth concentrate

Abstract

The invention discloses a mixed rare earth concentrate treatment method. The treatment method comprises the following steps that mixed rare earth concentrate reacts with first hydrochloric acid, and chemical separation ore and chemical separation liquid are obtained; roasting the chemical ore to obtain roasted ore; carrying out primary alkaline hydrolysis reaction on the roasted ore and a first alkaline solution to obtain a primary alkaline hydrolysis product; washing the primary alkaline hydrolysis solid product with water to obtain an alkali cake I and alkali washing liquid I; sodium fluoride in the washing alkali liquid I is separated out, and sodium fluoride and residual alkali I are obtained; carrying out a secondary alkaline hydrolysis reaction on raw materials comprising a phosphorus-containing material and a second alkaline solution to obtain a secondary alkaline hydrolysis product; washing the secondary alkaline hydrolysis solid product with water to obtain an alkali cake II and an alkali washing solution II; and separating out trisodium phosphate in the alkali washing liquid II to obtain trisodium phosphate and residual alkali II. According to the method, the fluorine element and the phosphorus element in the mixed rare earth concentrate can be recycled respectively, and the purity of the obtained sodium fluoride and trisodium phosphate is high.

Description

Technical Field

[0001] The invention relates to a method for processing mixed rare earth concentrate. Background Art

[0002] The Baotou Bayan Obo rare earth concentrate, the world's largest rare earth deposit in terms of proven reserves and mined output, is rich in rare earth resources. Currently, the main mineral-based rare earth ores that can be mined are bastnaesite, monazite, and mixed rare earth ores. Mixed rare earth concentrate is composed of bastnaesite and monazite, with the ratio typically ranging from 9:1 to 3:2. Due to its complex composition, mixed rare earth concentrate is considered difficult to smelt.

[0003] Currently, the main industrialized technologies for decomposing mixed rare earth concentrates include high-temperature roasting with concentrated sulfuric acid and atmospheric-pressure decomposition with concentrated alkali. The high-temperature roasting with concentrated sulfuric acid involves mixing rare earth concentrate with concentrated sulfuric acid and roasting it at 400-1000°C. During the reaction, the concentrate and concentrated sulfuric acid rapidly transform from a solid-liquid mixed phase to a pure solid phase. Excessively large mineral particles can lead to incomplete internal reactions, impacting the rare earth decomposition rate. Furthermore, this process produces large quantities of high-temperature mixed acidic gases, resulting in sulfate wastewater and radioactive residues that are difficult to treat, leading to a large and costly environmental treatment system. The concentrated alkali decomposition process, which treats mixed rare earth concentrates with an REO grade of approximately 60%, uses sodium hydroxide to decompose the rare earth minerals, generating large quantities of mixed alkaline wastewater. This makes resource recovery difficult and results in excessive sodium hydroxide waste. This waste must be simply neutralized and discharged to the sea to meet standards, without recovering resources such as fluorine and phosphorus.

[0004] CN102277484A discloses a method for separating and recovering sodium phosphate and sodium fluoride in an alkaline smelting process for mixed rare earth concentrate. The mixed rare earth concentrate is roasted at 450-600°C for 30-120 minutes; the roasted ore is leached with hydrochloric acid to obtain an acid leaching residue and an acid leaching solution; sodium hydroxide solution is added to the acid leaching residue after hydrochloric acid leaching for alkaline decomposition; the mineral after alkaline decomposition is washed with water, the washed slag is used to recover the rare earths, and the washing solution is used to separate and recover sodium phosphate and sodium fluoride. The washing is performed in a countercurrent washing method with 4-6 countercurrent washing stages; the first-stage washing solution during the countercurrent washing is heated and evaporated to obtain sodium fluoride crystals; the filtrate after evaporation, crystallization, and filtration is cooled to cause crystals to form, and the crystals are filtered and recovered as sodium phosphate; the condensed and crystallized liquid is further heated and concentrated to obtain a sodium hydroxide solution, which is used as a diluent for sodium hydroxide during alkaline decomposition of the mineral, and is then condensed or further evaporated to produce solid hydroxide. The sodium fluoride and sodium phosphate recovered by this method have low purity.

[0005] CN109536746A discloses a method for cyclic slurry decomposition of low-calcium, high-grade mixed rare earth concentrate, which comprises mixing the low-calcium, high-grade mixed rare earth concentrate with a sulfuric acid solution in proportion, performing a slurry reaction under heating, and decomposing fluorine-containing minerals. After tail gas absorption, a fluorine-silicon mixed acid byproduct is formed. After the reaction is completed, the solid-liquid separation is performed to obtain an acid leaching solution and an acid leaching residue. The acid leaching residue is leached in water to produce a leaching residue and a leaching solution. The leaching solution is neutralized to form a phospho-iron-thorium slag and a rare earth sulfate solution, with the generated calcium sulfate dissolving in the leaching solution in equilibrium. The acid leaching solution is then supplemented with sulfuric acid to continue processing new mixed rare earth concentrate. The leaching residue and phospho-iron-thorium slag are mixed with a sodium hydroxide solution containing 45-70% by weight, in a ratio of 1:0.1-0.8 (low-calcium, high-grade mixed rare earth concentrate) and slurried at 130-180°C for decomposition. The alkaline hydrolyzed ore is washed, dissolved in hydrochloric acid, neutralized, and impurities removed to form an acid slag, radioactive phospho-iron-thorium slag, and a rare earth chloride solution. The alkali wash wastewater is concentrated and crystallized to produce trisodium phosphate as a byproduct. The concentrated solution is supplemented with sodium hydroxide to continue decomposing the phosphorus-containing minerals and phospho-iron-thorium slag. This method requires a high grade of mixed rare earth concentrate. Summary of the Invention

[0006] In view of this, the present invention aims to provide a method for treating a mixed rare earth concentrate. The method can separately recover fluorine and phosphorus from the mixed rare earth concentrate, resulting in high-purity sodium fluoride and trisodium phosphate. Furthermore, the method achieves high recovery rates for fluorine and phosphorus. Furthermore, the method achieves a high rare earth leaching rate.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions.

[0008] The present invention provides a method for processing a mixed rare earth concentrate, comprising the following steps:

[0009] (1) reacting the mixed rare earth concentrate with a first hydrochloric acid to obtain a chemical separation solution;

[0010] (2) roasting the chemically separated ore to obtain roasted ore;

[0011] (3) subjecting the roasted ore to a primary alkaline hydrolysis reaction with a first alkaline solution at 100-135° C. to obtain a primary alkaline hydrolysis product; separating the primary alkaline hydrolysis product into a solid-liquid state to obtain a primary alkaline hydrolysis solid product and a primary alkaline hydrolysis liquid product; washing the primary alkaline hydrolysis solid product with water to obtain an alkaline cake I and an alkaline washing solution I; and precipitating sodium fluoride in the alkaline washing solution I to obtain sodium fluoride and residual alkali I;

[0012] Wherein, the alkaline substance in the first alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate;

[0013] (4) subjecting the raw materials including the phosphorus-containing material and the second alkaline solution to a secondary alkaline hydrolysis reaction at 140-180° C. to obtain a secondary alkaline hydrolysis product; separating the secondary alkaline hydrolysis product into a solid-liquid state to obtain a secondary alkaline hydrolysis solid product and a secondary alkaline hydrolysis liquid product; washing the secondary alkaline hydrolysis solid product with water to obtain an alkaline cake II and an alkaline washing solution II; and precipitating trisodium phosphate in the alkaline washing solution II to obtain trisodium phosphate and residual alkali II;

[0014] The alkaline substance in the second alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate, and the phosphorus-containing material is alkaline cake I or acid slag obtained by acid hydrolysis of alkaline cake I.

[0015] The processing method according to the present invention preferably further comprises the following steps:

[0016] During the reaction of the mixed rare earth concentrate with the first hydrochloric acid, a mixed acid of hydrochloric acid and hydrofluoric acid is obtained by spraying and absorbing the tail gas;

[0017] Calcium oxide is used to adjust the pH of the chemical separation solution to 7-9 to obtain a calcium chloride solution and rare earth phosphate precipitate;

[0018] The raw materials of step (4) also include rare earth phosphate precipitate.

[0019] According to the treatment method of the present invention, preferably, the phosphorus-containing material is an acid slag obtained by acid hydrolysis of the alkali cake I;

[0020] The method further comprises the following steps: reacting the alkaline cake I with a first solution containing hydrogen chloride to obtain an acid solution I and an acid residue.

[0021] According to the treatment method of the present invention, preferably, the calcination is carried out in an oxygen-free atmosphere or an oxygen-containing atmosphere, the calcination temperature is 400-600° C., and the calcination time is 1-5 hours.

[0022] According to the treatment method of the present invention, preferably, the concentration of the first alkaline solution is 10 to 50 wt%, the solid-liquid ratio of the roasted ore to the first alkaline solution is 1 kg: (1 to 3) L, the primary alkaline hydrolysis is carried out at a pressure of 0.1 to 1 MPa, and the reaction time of the primary alkaline hydrolysis is 0.5 to 4 h.

[0023] According to the treatment method of the present invention, preferably, the concentration of the second alkaline solution is 40 to 65 wt%;

[0024] In the raw materials of step (4), the solid-liquid ratio of the solid material to the second alkaline solution is 1 kg: (1-2.5) L;

[0025] The secondary alkaline hydrolysis is carried out at a pressure of 0.1 to 1 MPa, and the reaction time of the secondary alkaline hydrolysis is 0.5 to 4 hours.

[0026] According to the treatment method of the present invention, preferably, sodium fluoride in the alkali washing solution I is precipitated by concentration crystallization or salting out;

[0027] The trisodium phosphate in the alkali washing solution II is precipitated by cooling crystallization.

[0028] The processing method according to the present invention preferably further comprises the following steps:

[0029] The alkali cake II is dissolved in the second solution containing hydrogen chloride to obtain an acid solution II and leaching residue.

[0030] According to the processing method of the present invention, preferably, in the chemical separation, the content of REO is ≥65wt%, and the content of CaO is ≤2.5wt%.

[0031] According to the treatment method of the present invention, preferably, the purity of the sodium fluoride precipitated in step (3) is ≥96wt%, and the purity of the trisodium phosphate obtained in step (4) is ≥95.5wt%.

[0032] The method of the present invention can separately recover fluorine and phosphorus from a mixed rare earth concentrate, resulting in high-purity sodium fluoride and trisodium phosphate. Furthermore, the method of the present invention has high recovery rates for fluorine and phosphorus. Furthermore, the method of the present invention has a high rare earth leaching rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of a method for processing mixed rare earth concentrate. DETAILED DESCRIPTION

[0034] 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.

[0035] The method for treating a mixed rare earth concentrate of the present invention comprises the following steps: (1) a hydrochloric acid separation step; (2) a roasting step; (3) a primary alkaline hydrolysis step; and (4) a secondary alkaline hydrolysis step. In certain embodiments, the method further comprises an acid dissolution step. Each step is described in detail below.

[0036] Steps of hydrochloric acid separation

[0037] The mixed rare earth concentrate is reacted with hydrochloric acid to obtain chemical separation and chemical separation liquid.

[0038] The REO content in the mixed rare earth concentrate may be 45 wt% or greater, preferably 50 wt% or greater, and more preferably 55 wt% or greater. The REO content may be 60 wt% or less. In certain embodiments, the REO content is 56 wt% or less.

[0039] In the mixed rare earth concentrate, the CaO content may be 15 wt% or less, preferably 12 wt% or less, and more preferably 10 wt% or less. The CaO content may be 5 wt% or more, and preferably 9 wt% or more.

[0040] The concentration of hydrochloric acid may be 2 to 6 mol / L, preferably 3 to 5 mol / L, and more preferably 4 to 5 mol / L.

[0041] The solid-liquid ratio of the mixed rare earth concentrate to hydrochloric acid can be 1:(1-8); preferably 1:(2-6); more preferably 1:(3-4).

[0042] The reaction time of the mixed rare earth concentrate and hydrochloric acid can be 30 to 200 minutes, preferably 60 to 180 minutes, and more preferably 100 to 150 minutes.

[0043] The reaction temperature of the mixed rare earth concentrate and hydrochloric acid can be 80-150°C, preferably 85-100°C, and more preferably 90-95°C.

[0044] This is beneficial to improving the grade of mixed rare earth concentrate and facilitating the recovery of fluorine, phosphorus and rare earth elements.

[0045] During the reaction of the mixed rare earth concentrate with hydrochloric acid, a mixed acid of hydrochloric acid and hydrofluoric acid can be obtained by spraying and absorbing the tail gas.

[0046] In the chemical beneficiation, the content of REO may be greater than or equal to 65 wt %, preferably, the content of REO is 68-75 wt %, and in certain embodiments, the content of REO is 69-72 wt %.

[0047] In the chemical beneficiation, the CaO content may be less than or equal to 2.5 wt %. Preferably, the CaO content is 1 to 2 wt %. In certain embodiments, the CaO content is 1.5 to 1.9 wt %.

[0048] In certain embodiments, the process further includes adjusting the pH of the separation solution to 7-9 using calcium oxide to produce a calcium chloride solution and a rare earth phosphate precipitate. Preferably, the pH of the separation solution is adjusted to 8-8.5 using calcium oxide to produce a calcium chloride solution and a rare earth phosphate precipitate. This helps improve the recovery rate of phosphorus and rare earth elements.

[0049] Roasting steps

[0050] The chemically separated ore is roasted to obtain roasted ore.

[0051] Calcination can be carried out in an oxygen-containing atmosphere or an oxygen-free atmosphere. The oxygen-containing atmosphere can be an air atmosphere. The oxygen-free atmosphere can be an inert gas atmosphere, such as a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, etc.

[0052] The calcination temperature may be 400-600° C. In certain embodiments, the calcination temperature is 400-430° C. In other embodiments, the calcination temperature is 500-520° C.

[0053] The calcination time may be 1 to 5 hours. In certain embodiments, the calcination time is 2 to 3 hours. In other embodiments, the calcination time is 3.5 to 4 hours.

[0054] This is conducive to the roasting and decomposition of the ore, and the resulting roasted ore is easy to alkaline hydrolysis.

[0055] Steps of primary alkaline hydrolysis

[0056] The roasted ore is subjected to a primary alkaline hydrolysis reaction with a first alkaline solution at 100-135° C. to obtain a primary alkaline hydrolysis product; the primary alkaline hydrolysis product is subjected to solid-liquid separation to obtain a primary alkaline hydrolysis solid product and a primary alkaline hydrolysis liquid product; the primary alkaline hydrolysis solid product is washed with water to obtain an alkaline cake I and an alkaline washing solution I; and sodium fluoride in the alkaline washing solution I is precipitated to obtain sodium fluoride and residual alkali I.

[0057] The primary alkaline hydrolysis temperature is 100-135° C. In certain embodiments, the primary alkaline hydrolysis temperature is 100-110° C. In other embodiments, the primary alkaline hydrolysis temperature is 110-120° C. In yet other embodiments, the primary alkaline hydrolysis temperature is 120-135° C.

[0058] The first alkaline solution is a solution formed by an alkaline substance and water. The alkaline substance in the first alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate. Preferably, the alkaline substance in the first alkaline solution is sodium hydroxide.

[0059] The concentration of the first alkaline solution may be 10 to 50 wt %. In some embodiments, the concentration of the first alkaline solution is 20 to 30 wt %. In other embodiments, the concentration of the first alkaline solution is 37 to 40 wt %.

[0060] The solid-liquid ratio of the roasted ore to the first alkaline solution may be 1 kg: (1-3) L. In certain embodiments, the solid-liquid ratio of the roasted ore to the first alkaline solution is 1 kg: (1.5-2.5) L. In other embodiments, the solid-liquid ratio of the roasted ore to the first alkaline solution is 1 kg: (2-2.3) L.

[0061] The primary alkaline hydrolysis can be carried out at a pressure of 0.1 to 1 MPa. In certain embodiments, the primary alkaline hydrolysis is carried out at a pressure of 0.2 to 0.6 MPa. In other embodiments, the primary alkaline hydrolysis is carried out at a pressure of 0.4 to 0.5 MPa.

[0062] The reaction time of one alkaline hydrolysis can be 0.5 to 4 hours, preferably 1 to 3 hours. In certain embodiments, the reaction time of one alkaline hydrolysis is 2 to 3 hours.

[0063] This helps to fully recover the fluorine element in the roasted ore and improve the purity of sodium fluoride.

[0064] The solid-liquid separation of the primary alkaline hydrolysis product is carried out to obtain a primary alkaline hydrolysis solid product and a primary alkaline hydrolysis liquid product.

[0065] The sodium fluoride in the alkali washing solution I can be precipitated by concentrated crystallization or salting out. The liquid product of the primary alkaline hydrolysis and the residual alkali I can be used to prepare the first alkaline solution.

[0066] The purity of sodium fluoride may be greater than or equal to 96 wt %; preferably, the purity of sodium fluoride is greater than or equal to 96.5 wt %; more preferably, the purity of sodium fluoride is greater than or equal to 97 wt %.

[0067] The recovery rate of fluorine element may be greater than or equal to 94 wt %; preferably, the recovery rate of fluorine element is greater than or equal to 95 wt %; more preferably, the recovery rate of fluorine element is greater than or equal to 96 wt %.

[0068] Secondary alkaline hydrolysis steps

[0069] The raw materials including the phosphorus-containing material and the second alkaline solution are subjected to a secondary alkaline hydrolysis reaction at 140-180° C. to obtain a secondary alkaline hydrolysis product; the secondary alkaline hydrolysis product is subjected to solid-liquid separation to obtain a secondary alkaline hydrolysis solid product and a secondary alkaline hydrolysis liquid product; the secondary alkaline hydrolysis solid product is washed with water to obtain an alkaline cake II and an alkaline washing solution II; and trisodium phosphate in the alkaline washing solution II is precipitated to obtain trisodium phosphate and residual alkali II.

[0070] The phosphorus-containing material can be alkali cake 1 or acid slag obtained by acid hydrolysis of alkali cake 1. In some embodiments, the phosphorus-containing material is alkali cake 1. In other embodiments, the phosphorus-containing material is acid slag obtained by acid hydrolysis of alkali cake 1.

[0071] In certain embodiments, the method further comprises the step of reacting the alkaline cake I with a first solution containing hydrogen chloride to obtain an acid solution I and an acid residue.

[0072] The first hydrogen chloride-containing solution can be selected from one of hydrochloric acid, acid solution I, acid solution II, or a mixed acid of hydrochloric acid and hydrofluoric acid obtained by spraying and absorbing tail gas.

[0073] In the first hydrogen chloride-containing solution, the concentration of hydrogen chloride may be 6 to 12 mol / L, preferably 8 to 12 mol / L, and more preferably 10 to 12 mol / L.

[0074] The solid-to-liquid ratio of the alkali cake I to the first hydrogen chloride-containing solution may be 1:(1-6) kg / L, preferably 1:(2-5) kg / L, and more preferably 1:(3-4) kg / L.

[0075] The reaction temperature of the alkaline cake I and the first hydrogen chloride-containing solution can be 80-115°C, preferably 85-105°C, and more preferably 90-95°C.

[0076] The reaction time of the alkaline cake I and the first hydrogen chloride-containing solution can be 0.5 to 5 hours, preferably 1 to 4 hours, and more preferably 2 to 3 hours.

[0077] The reaction temperature of the secondary alkaline hydrolysis reaction is 140-180° C. In certain embodiments, the reaction temperature of the secondary alkaline hydrolysis reaction is 140-150° C. In other embodiments, the reaction temperature of the secondary alkaline hydrolysis reaction is 160-170° C.

[0078] The second alkaline solution is a solution formed by an alkaline substance and water. The alkaline substance in the second alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate. Preferably, the alkaline substance in the first alkaline solution is sodium hydroxide.

[0079] The concentration of the second alkaline solution may be 40 to 65 wt %. In some embodiments, the concentration of the second alkaline solution is 50 to 65 wt %. In other embodiments, the concentration of the second alkaline solution is 60 to 63 wt %.

[0080] In the raw materials, the solid-liquid ratio of the solid material to the second alkaline solution can be 1 kg: (1 to 2.5) L. In certain embodiments, the solid-liquid ratio of the solid material to the second alkaline solution is 1 kg: (1.5 to 2.5) L. In other embodiments, the solid-liquid ratio of the solid material to the second alkaline solution is 1 kg: (2 to 2.3) L. In certain embodiments, the solid material can be acid slag. In other embodiments, the solid material is acid slag and rare earth phosphate precipitate. In still other embodiments, the solid material is alkali cake I. In yet other embodiments, the solid material is alkali cake I and rare earth phosphate precipitate.

[0081] The secondary alkaline hydrolysis can be carried out at a pressure of 0.1 to 1 MPa. In certain embodiments, the secondary alkaline hydrolysis is carried out at a pressure of 0.2 to 0.6 MPa. In other embodiments, the secondary alkaline hydrolysis is carried out at a pressure of 0.8 to 0.9 MPa.

[0082] The reaction time of the secondary alkaline hydrolysis can be 0.5 to 4 hours, preferably 0.5 to 2 hours. In certain embodiments, the reaction time of the secondary alkaline hydrolysis is 0.5 to 1.5 hours.

[0083] This helps fully recover the phosphorus element in the alkali cake I and improves the purity of trisodium phosphate.

[0084] The trisodium phosphate in the alkali washing solution II can be precipitated by concentration crystallization or salting out.

[0085] The secondary alkaline hydrolysis liquid product and the residual base II can be used to prepare the second alkaline solution.

[0086] The purity of trisodium phosphate may be greater than or equal to 95.5 wt %; preferably, the purity of trisodium phosphate is greater than or equal to 97 wt %; more preferably, the purity of trisodium phosphate is greater than or equal to 98 wt %.

[0087] The recovery rate of phosphorus is greater than or equal to 97 wt %; preferably, the recovery rate of phosphorus is greater than or equal to 98 wt %; more preferably, the recovery rate of phosphorus is greater than or equal to 98.5 wt %.

[0088] Acid dissolution steps

[0089] The alkali cake II is dissolved in a second solution containing hydrogen chloride to obtain an acid solution II and leached residue. In certain embodiments, the process further comprises mixing the acid solution I and the acid solution II.

[0090] The second solution containing hydrogen chloride can be selected from hydrochloric acid, acid solution I, acid solution II, or a mixed acid of hydrochloric acid and hydrofluoric acid obtained by spraying and absorbing tail gas. According to one embodiment of the present invention, the second solution containing hydrogen chloride is hydrochloric acid.

[0091] The concentration of hydrogen chloride in the second hydrogen chloride-containing solution may be 6 to 12 mol / L, preferably 8 to 12 mol / L, and more preferably 9 to 12 mol / L.

[0092] The solid-to-liquid ratio of the alkali cake II to the second hydrogen chloride-containing solution may be 1:(1-6) kg / L, preferably 1:(2-5) kg / L, and more preferably 1:(3-4) kg / L.

[0093] The reaction temperature of the alkaline cake II and the second hydrogen chloride-containing solution may be 80-115°C, preferably 85-105°C, and more preferably 90-95°C.

[0094] The reaction time of the alkaline cake II and the second hydrogen chloride-containing solution can be 0.5 to 3 hours, preferably 1 to 2.5 hours, and more preferably 1.5 to 2 hours.

[0095] The leaching rate of rare earth may be greater than or equal to 97 wt %; preferably, greater than or equal to 98 wt %; more preferably, greater than or equal to 98.5 wt %.

[0096] Here is the test method:

[0097] Purity of sodium fluoride: tested using the method specified in YS / T 517-2024.

[0098] Purity of trisodium phosphate: tested using the method specified in HG / T2517-2009.

[0099] The recovery rate of fluorine element is: (the mass of fluorine element contained in the obtained sodium fluoride / the mass of fluorine element contained in the mineral separation)×100%.

[0100] Recovery rate of phosphorus: (mass of phosphorus contained in the obtained trisodium phosphate / mass of phosphorus contained in the chemically separated ore) × 100%.

[0101] Leaching rate of rare earth: (mass of rare earth elements contained in rare earth chloride solution / mass of rare earth elements in mixed rare earth concentrate) × 100%.

[0102] Here are the raw materials:

[0103] The mixed rare earth concentrate comes from the Bayan Obo mining area in Baotou City, Inner Mongolia Autonomous Region.

[0104] Example 1 to Example 5

[0105] (1) The mixed rare earth concentrate is reacted with a first hydrochloric acid to obtain a chemical separation solution. During the reaction, tail gas is absorbed by spraying water to obtain a mixed acid of hydrochloric acid and hydrofluoric acid. Calcium oxide is added to the chemical separation solution to neutralize it to a pH value of A (representing a certain value), thereby obtaining a calcium chloride solution and a rare earth phosphate precipitate.

[0106] (2) roasting the chemically separated ore to obtain roasted ore.

[0107] (3) subjecting the roasted ore to a primary alkaline hydrolysis reaction with the first sodium hydroxide solution to obtain a primary alkaline hydrolysis product. The primary alkaline hydrolysis product is subjected to solid-liquid separation to obtain a primary alkaline hydrolysis solid product and a primary alkaline hydrolysis liquid product. The primary alkaline hydrolysis solid product is washed with water to obtain an alkaline cake I and an alkaline washing solution I. The alkaline washing solution I is concentrated and crystallized to obtain sodium fluoride and residual alkali I. The primary alkaline hydrolysis liquid product and the residual alkali I are used to prepare the sodium hydroxide solution.

[0108] (4) reacting the alkali cake I with the second hydrochloric acid to obtain an acid solution I and an acid residue. The acid residue, the rare earth phosphate precipitate and the second sodium hydroxide solution are subjected to a secondary alkaline hydrolysis reaction to obtain a secondary alkaline hydrolysis product. The secondary alkaline hydrolysis product is separated into a solid and a liquid product of secondary alkaline hydrolysis to obtain an alkaline cake II and an alkaline washing solution II. The alkaline washing solution II is cooled and crystallized to obtain trisodium phosphate and residual alkali II. The secondary alkaline hydrolysis liquid product and the residual alkali II are used to prepare the sodium hydroxide solution.

[0109] The alkali cake II is dissolved with the third hydrochloric acid to obtain an acid solution II and leaching residue. The acid solution I and the acid solution II are combined to obtain a rare earth chloride solution.

[0110] The raw materials and parameters of each step of Examples 1 to 5 are shown in Table 1. The purity of sodium fluoride, the recovery rate of fluorine, the purity of trisodium phosphate, the recovery rate of phosphorus, and the leaching rate of rare earth are also shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] Note: The first hydrochloric acid, the second hydrochloric acid, and the third hydrochloric acid all refer to hydrochloric acid, and the "first," "second," and "third" are only used to distinguish them. The first sodium hydroxide solution and the second sodium hydroxide solution all refer to sodium hydroxide solution, and the "first" and "second" are only used to distinguish them.

[0115] As shown in Table 1, the method of the present invention can recover fluorine, phosphorus, and rare earth elements from the mixed rare earth concentrate. By controlling the above process parameters, the purity of sodium fluoride and trisodium phosphate can be increased, and the recovery rates of fluorine and phosphorus, as well as the leaching rate of rare earths, can be improved.

[0116] 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 processing mixed rare earth concentrate, characterized in that: The steps include: (1) reacting the mixed rare earth concentrate with a first hydrochloric acid to obtain a chemical separation solution; (2) roasting the chemically separated ore to obtain roasted ore; (3) subjecting the roasted ore to a primary alkaline hydrolysis reaction with a first alkaline solution at 100-135° C. to obtain a primary alkaline hydrolysis product; separating the primary alkaline hydrolysis product into a solid-liquid state to obtain a primary alkaline hydrolysis solid product and a primary alkaline hydrolysis liquid product; washing the primary alkaline hydrolysis solid product with water to obtain an alkaline cake I and an alkaline washing solution I; and precipitating sodium fluoride in the alkaline washing solution I to obtain sodium fluoride and residual alkali I; Wherein, the alkaline substance in the first alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate; (4) subjecting the raw materials including the phosphorus-containing material and the second alkaline solution to a secondary alkaline hydrolysis reaction at 140-180° C. to obtain a secondary alkaline hydrolysis product; separating the secondary alkaline hydrolysis product into a solid-liquid state to obtain a secondary alkaline hydrolysis solid product and a secondary alkaline hydrolysis liquid product; washing the secondary alkaline hydrolysis solid product with water to obtain an alkaline cake II and an alkaline washing solution II; and precipitating trisodium phosphate in the alkaline washing solution II to obtain trisodium phosphate and residual alkali II; The alkaline substance in the second alkaline solution is selected from one or more of sodium hydroxide and sodium carbonate, and the phosphorus-containing material is alkaline cake I or acid slag obtained by acid hydrolysis of alkaline cake I.

2. The processing method according to claim 1, characterized in that The following steps are also included: During the reaction of the mixed rare earth concentrate with the first hydrochloric acid, a mixed acid of hydrochloric acid and hydrofluoric acid is obtained by spraying and absorbing the tail gas; Calcium oxide is used to adjust the pH of the chemical separation solution to 7-9 to obtain a calcium chloride solution and rare earth phosphate precipitate; The raw materials of step (4) also include rare earth phosphate precipitate.

3. The processing method according to claim 1, characterized in that The phosphorus-containing material is an acid slag obtained by acid hydrolysis of alkali cake I; The method further comprises the following steps: reacting the alkaline cake I with a first solution containing hydrogen chloride to obtain an acid solution I and an acid residue.

4. The processing method according to claim 1, characterized in that The calcination is carried out in an oxygen-free atmosphere or an oxygen-containing atmosphere, the calcination temperature is 400-600° C., and the calcination time is 1-5 hours.

5. The processing method according to claim 1, characterized in that The concentration of the first alkaline solution is 10-50 wt %, the solid-liquid ratio of the roasted ore to the first alkaline solution is 1 kg: (1-3) L, the primary alkaline hydrolysis is carried out at a pressure of 0.1-1 MPa, and the reaction time of the primary alkaline hydrolysis is 0.5-4 h.

6. The processing method according to claim 1, characterized in that The concentration of the second alkaline solution is 40 to 65 wt %; In the raw materials of step (4), the solid-liquid ratio of the solid material to the second alkaline solution is 1 kg: (1-2.5) L; The secondary alkaline hydrolysis is carried out at a pressure of 0.1 to 1 MPa, and the reaction time of the secondary alkaline hydrolysis is 0.5 to 4 hours.

7. The processing method according to claim 1, characterized in that The sodium fluoride in the alkali washing solution I is precipitated by a concentrated crystallization or salting-out method; The trisodium phosphate in the alkali washing solution II is precipitated by cooling crystallization.

8. The processing method according to claim 1, characterized in that The following steps are also included: The alkali cake II is dissolved in the second hydrogen chloride-containing solution to obtain an acid solution II and leaching residue.

9. The processing method according to claim 1, characterized in that: In the chemical mineral separation, the content of REO is ≥65wt%, and the content of CaO is ≤2.5wt%.

10. The processing method according to any one of claims 1 to 9, characterized in that: The purity of the sodium fluoride precipitated in step (3) is ≥96wt%, and the purity of the trisodium phosphate obtained in step (4) is ≥95.5wt%.

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