A method for continuous preparation of rare earth compound precipitation

Abstract

This invention relates to the field of continuous rare earth compound precipitation, and discloses a method for continuous rare earth compound precipitation, comprising the following steps: dilution and activation: fine crystal slurry, rare earth feed solution, and recycled precipitation wastewater are added to an activation preparation tank via a flow controller, and then stirred to obtain a mixed solution; crystal nucleus growth: the mixed solution overflows into a growth precipitation tank, and then ammonium bicarbonate solution is added and stirred to obtain a crystal nucleus growth slurry; complete crystallization: the crystal nucleus growth slurry overflows into a crystallization precipitation tank, and then ammonium bicarbonate solution is added again and stirred. By dividing the entire continuous precipitation process into steps such as dilution and activation, crystal nucleus growth, complete crystallization, static aging, and graded unloading, and by overflowing in stages, segmented continuous control is achieved. Different reaction stages are controlled in their respective individual reaction tanks. Through staged overflow, precise control is achieved in stages, and the entire reaction process is continuously controllable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous preparation of rare earth compound precipitation, in particular to a method for continuously preparing rare earth compound precipitation. BACKGROUND

[0002] Rare earth metals have extremely important uses, and are important components of contemporary high-tech new materials. A series of compounds composed of rare earth metals and non-ferrous metals, such as semiconductor, electronic-optical material, special alloy, new functional material, and organometallic compound, all require rare earth metals with unique properties. Although the amount of rare earth metals used is not large, they are crucial and indispensable. Therefore, they are widely used in contemporary communication technology, electronic computers, space development, medicine and health, photosensitive materials, photoelectric materials, energy materials, and catalyst materials. China is rich in rare earth metal minerals, providing good resource conditions for the development of the rare earth metal industry.

[0003] In the traditional rare earth precipitation process, intermittent reactions are carried out in a single reaction kettle, which cannot be continuously carried out. This preparation method not only makes the operation cumbersome and labor-intensive, but also has high energy consumption. Since it relies on manual intermittent production operation by operators, the consistency of the produced products is poor, and the crystal form, particle size, and distribution of rare earths also have great fluctuations. Therefore, it is necessary to propose a method for continuously preparing rare earth compound precipitation to solve the above problems. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a method for continuously preparing rare earth compound precipitation, which solves the problem that the traditional rare earth precipitation process is intermittent in a single reaction kettle and cannot be continuously carried out.

[0005] To achieve the above object, the present application is implemented by the following technical scheme: a method for continuously preparing rare earth compound precipitation, comprising the following steps:

[0006] S1, dilution and activation: the fine crystal slurry, rare earth solution and recycled precipitation wastewater are added to the activation configuration tank through the flow controller, and then stirred to obtain a mixed solution;

[0007] S2, crystal nucleus growth: the mixed solution is overflowed into the growth precipitation tank, then ammonium carbonate solution is added, and stirring treatment is carried out to obtain crystal nucleus growth slurry;

[0008] S3, complete crystallization: the crystal nucleus growth slurry is overflowed into the crystallization precipitation tank, then ammonium carbonate solution is added again, and stirring treatment is carried out to obtain completely crystallized slurry;

[0009] S4, standing and aging: the completely crystallized slurry is overflowed into an aging precipitation tank, a precipitant is added and stirring treatment is performed, so that crystallized rare earth carbonate slurry is obtained;

[0010] S5, grading and discharging: the crystallized rare earth carbonate slurry is overflowed into a grading and discharging tank, fine crystal grains in the crystallized rare earth carbonate slurry are guided to a crystal slurry transfer tank by a rare earth liquid, and are pumped back to the activation and configuration tank; the remaining crystallized rare earth carbonate slurry is transported to a slurry transfer tank through a discharging port, and is pumped to a vacuum belt filter for filtration, so that large particle rare earth carbonate is obtained.

[0011] Preferably, the fine crystal slurry in step S1 includes the fine crystal grains in step S5, and the stirring treatment includes a stirring speed of 50-120 r / min and a reaction temperature of 40-80℃.

[0012] Preferably, the stirring treatment in step S2 includes a stirring speed of 50-120 r / min, a reaction temperature of 40-80℃, a slurry acid-base degree of 4.8-5.5, and a reaction time of 0.5-1 hour.

[0013] Preferably, the stirring treatment in step S3 includes a stirring speed of 50-120 r / min, a reaction temperature of 40-80℃, a slurry acid-base degree of 6.4-6.8, a reaction time of 0.5-1 hour, and a rare earth content in supernatant of the completely crystallized slurry of less than 0.07 g / L.

[0014] Preferably, the stirring treatment in step S4 includes a stirring speed of 20-40 r / min, a reaction temperature of 40-80℃, a slurry acid-base degree of 6.4-6.8, an aging time of 0.5-1 hour, the precipitant is one or more of ammonium bicarbonate and ammonia water mixed, and the concentration is 0.5-1.5 mol / L.

[0015] Preferably, the addition amount of the fine crystal slurry in step S1 is 15%-25% of the rare earth tank amount, the concentration of rare earth ions in the rare earth liquid is 1.2-1.8 mol / L, and the concentration of rare earth ions in the mixed liquid is 0.2-0.8 mol / L.

[0016] Preferably, a pH meter is arranged in each of the activation and configuration tank, the growth precipitation tank, the crystallization precipitation tank, and the aging precipitation tank, a carbon ammonium flow meter is arranged on one side of each of the growth precipitation tank and the crystallization precipitation tank, and the carbon ammonium flow meter on one side of each of the growth precipitation tank and the crystallization precipitation tank is connected with the pH meter arranged in each of the growth precipitation tank and the crystallization precipitation tank.

[0017] Preferably, the grading discharge chute comprises a grading zone and a discharge zone, the settling rate of the grading zone corresponds to a particle size greater than 80% of the particle size of the mass fraction of the crystallized rare earth carbonate slurry, and the grading zone comprises a slurry transfer tank, and the discharge zone comprises a slurry transfer tank.

[0018] The present application provides a continuous preparation method of rare earth compound precipitation.

[0019] 1、The present application divides the whole continuous precipitation process into dilution activation, crystal nucleus growth, complete crystallization, standing aging and grading discharge steps, and realizes step-by-step overflow to achieve segmented continuous control, and the whole process decomposes the single-stage precipitation tank into several smaller volume series reaction tanks, divides the carbon precipitation reaction process, controls different reaction stages in the respective single reaction tank, realizes precise control by step-by-step overflow, and realizes continuous control of the whole reaction process, thereby solving the problem that the traditional rare earth precipitation process is intermittent reaction in a single reaction kettle and cannot be continuously performed.

[0020] 2、The present application realizes the crystal type control of the rare earth carbonate precipitation as a whole by grading discharge of the obtained precipitation crystal slurry, that is, pumping part of the fine crystal precipitation into a configuration tank for use as a crystal seed, and drying the other part by centrifugal filtration to obtain rare earth carbonate; thus, the obtained rare earth carbonate product has the effects of large particle size, high specific gravity, good operation continuity and high labor productivity, and because of continuous production, the reaction has strong consistency, so that the produced product has strong consistency.

[0021] 3、In the production process, the rare earth compound precipitate formed simultaneously is automatically and continuously discharged as the rare earth solution and the precipitant are continuously injected, realizing continuous production, providing convenience for subsequent production processes, and the produced rare earth compound product has fine crystallization, high particle size concentration, and few non-rare earth impurities, the process of the present application is simple and reasonable, the device structure is simple, operation is convenient, maintenance is easy, investment is small, effect is good, and it is beneficial for enterprises to reduce production cost and increase benefit. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A method flow chart of a continuous preparation method of rare earth compound precipitation is provided for the present application. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described clearly and completely below in combination with the drawings of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] Embodiment:

[0025] Please refer to the attached Figure 1 The embodiment of the present application provides a continuous preparation method of rare earth compound precipitation, comprising the following steps:

[0026] S1, dilution and activation: the fine crystal slurry, the rare earth solution and the recycled precipitation wastewater are added into the activation configuration tank through the flow controller, and then stirring treatment is performed, so that the mixed solution is obtained;

[0027] S2, crystal nucleus growth: the mixed solution is overflowed into the growth precipitation tank, then the ammonium carbonate solution is added, and stirring treatment is performed, so that the crystal nucleus growth slurry is obtained;

[0028] S3, complete crystallization: the crystal nucleus growth slurry is overflowed into the crystallization precipitation tank, then the ammonium carbonate solution is added again, and stirring treatment is performed, so that the completely crystallized slurry is obtained;

[0029] S4, standing and aging: the completely crystallized slurry is overflowed into the aging precipitation tank, the precipitant is added, and stirring treatment is performed, so that the crystalline rare earth carbonate slurry is obtained;

[0030] S5, grading unloading: the crystalline rare earth carbonate slurry is overflowed into the grading unloading tank, the fine crystal grains in the crystalline rare earth carbonate slurry are introduced into the crystal slurry transfer tank through the rare earth solution, and are pumped back to the activation configuration tank; the remaining crystalline rare earth carbonate slurry is transported to the slurry transfer tank through the unloading port, and is pumped to the vacuum belt filter for filtration, so that the large particle rare earth carbonate is obtained.

[0031] Specifically, the fine crystal slurry, the rare earth solution and the recycled precipitation wastewater are added into the activation preparation tank through the flow controller, and then stirring treatment is performed, so as to obtain the mixed solution, so as to dilute the concentration of the rare earth solution and activate the crystal seeds; the mixed solution overflows into the growth precipitation tank, then the ammonium carbonate solution is added, and stirring treatment is performed, so as to obtain the crystal nucleus growth slurry, so that the crystal nucleus is fully generated and grown; the crystal nucleus growth slurry overflows into the crystallization precipitation tank, then the ammonium carbonate solution is added again, and stirring treatment is performed, so as to obtain the completely crystallized slurry, so as to ensure complete precipitation and make the rare earth content in the supernatant of the completely crystallized slurry less than 0.07 g / L; the completely crystallized slurry overflows into the aging precipitation tank, the precipitant is added, and stirring treatment is performed, so as to obtain the crystalline rare earth carbonate slurry, so that the rare earth carbonate is crystallized; the crystalline rare earth carbonate slurry overflows into the grading discharge tank, the fine crystal grains in the crystalline rare earth carbonate slurry are guided into the slurry transfer tank through the rare earth solution, and are pumped back to the activation preparation tank; the remaining crystalline rare earth carbonate slurry is pumped to the slurry transfer tank through the discharge port, and then is pumped to the vacuum belt filter for filtration, so as to obtain the large particle rare earth carbonate, so as to complete the continuous preparation of the rare earth compound precipitation, by dividing the whole continuous precipitation process into the steps of dilution and activation, crystal nucleus growth, complete crystallization, static aging and grading discharge, and gradually overflowing, the segmented continuous control is realized, and the whole process divides the single-stage precipitation tank into several smaller volume series reaction tanks, divides the carbon deposition reaction process, controls different reaction stages in the respective single reaction tank, realizes the precise control by gradual overflow, and the whole reaction process is continuously controllable, so as to solve the problem that the traditional rare earth precipitation process is intermittent in the single reaction kettle and cannot be continuously performed.

[0032] The fine crystal slurry in step S1 includes the fine crystal grains in step S5, and the stirring treatment includes stirring speed of 50-120 r / min and reaction temperature of 40-80 °C; the addition amount of the fine crystal slurry in step S1 is 15%-25% of the rare earth tank amount, and the concentration of the rare earth ions in the rare earth solution is 1.2-1.8 mol / L, and the concentration of the rare earth ions in the mixed solution is 0.2-0.8 mol / L.

[0033] Specifically, the stirring speed is controlled to be 50-120 r / min, the reaction temperature is controlled to be 40-80 °C, the addition amount of the fine crystal slurry is controlled to be 15%-25% of the rare earth tank amount, and the concentration of the rare earth ions in the rare earth solution is controlled to be 1.2-1.8 mol / L, so as to dilute the concentration of the rare earth solution and activate the crystal seeds.

[0034] The stirring treatment in step S2 includes stirring speed of 50-120 r / min, reaction temperature of 40-80℃, slurry acidity and alkalinity of 4.8-5.5, and reaction time of 0.5-1 hour.

[0035] Specifically, the stirring speed is controlled to be 50-120 r / min, the reaction temperature is controlled to be 40-80℃, the slurry acidity and alkalinity is controlled to be 4.8-5.5, and the reaction time is controlled to be 0.5-1 hour, so that the crystal nucleus is fully generated and grown.

[0036] The stirring treatment in step S3 includes stirring speed of 50-120 r / min, reaction temperature of 40-80℃, slurry acidity and alkalinity of 6.4-6.8, and reaction time of 0.5-1 hour, and the rare earth content in the supernatant of the completely crystallized slurry is less than 0.07 g / L.

[0037] Specifically, the stirring speed is controlled to be 50-120 r / min, the reaction temperature is controlled to be 40-80℃, the slurry acidity and alkalinity is controlled to be 6.4-6.8, and the reaction time is controlled to be 0.5-1 hour, so that the rare earth content in the supernatant of the completely crystallized slurry is less than 0.07 g / L, and the precipitation is ensured to be complete.

[0038] The stirring treatment in step S4 includes stirring speed of 20-40 r / min, reaction temperature of 40-80℃, slurry acidity and alkalinity of 6.4-6.8, aging time of 0.5-1 hour, and the precipitant is one or more of ammonium bicarbonate and ammonia water mixed at a concentration of 0.5-1.5 mol / L.

[0039] Specifically, the stirring speed is controlled to be 20-40 r / min, the reaction temperature is controlled to be 40-80℃, the slurry acidity and alkalinity is controlled to be 6.4-6.8, the aging time is controlled to be 0.5-1 hour, and the precipitant is one or more of ammonium bicarbonate and ammonia water mixed at a concentration of 0.5-1.5 mol / L, so that the rare earth carbonate is crystallized.

[0040] The inside of the activation configuration tank, the growth precipitation tank, the crystallization precipitation tank, and the aging precipitation tank is provided with a pH meter, and the growth precipitation tank and the crystallization precipitation tank are provided with a carbon ammonium flow meter on one side, and the carbon ammonium flow meter on one side of the growth precipitation tank and the crystallization precipitation tank is connected with the pH meter inside the growth precipitation tank and the crystallization precipitation tank.

[0041] Specifically, the pH meter is used to monitor the pH value of the solution in each tank, and the ammonium carbonate flow meter is used to adjust the feeding rate of the ammonium carbonate solution according to the pH value of the solution. During the production process, as the rare earth solution and the precipitant are continuously injected, the formed rare earth compound precipitate can be continuously discharged, realizing continuous production and providing convenience for subsequent production processes. The produced rare earth compound product has fine crystal, high particle size concentration, and less non-rare earth impurities. The process of the present application is simple and reasonable, the device structure is simple, the operation is convenient, and the maintenance is easy. The present application has the advantages of low investment, good effect, and is beneficial to enterprises to reduce production cost and increase benefit.

[0042] The grading discharge tank comprises a grading zone and a discharge zone, the particle size corresponding to the settling rate of the grading zone is greater than the particle size of 80% of the mass fraction of the crystalline carbonic acid rare earth slurry, and the grading zone comprises a crystalline slurry transfer tank, and the discharge zone comprises a slurry transfer tank.

[0043] Specifically, the setting of the grading zone enables the crystals to be suspended in the grading zone in the form of a dynamic bed layer. Here, the particles with a mass fraction lower than 80% are carried away by the fluid because the particle size is smaller than the particle size corresponding to the settling rate of the grading zone, i.e., the settling rate of the particles with a mass fraction lower than 80% is lower than the flow rate of the grading zone, so that they are ultimately pumped back to the activation configuration tank. The particles with a mass fraction higher than 80% have a particle size greater than the particle size corresponding to the settling rate of the grading zone, so that they settle in the discharge zone and are pumped to the vacuum belt filter for further processing to obtain large-particle carbonic acid rare earth. The obtained precipitated crystal slurry is graded and discharged, i.e., part of the fine crystals is pumped into the activation configuration tank to be used as seed crystals, and the other part is dried by centrifugal filtration to obtain carbonic acid rare earth. Thus, the crystal type control of the carbonic acid rare earth precipitate is realized as a whole, so that the obtained carbonic acid rare earth product has large particles, high specific gravity, good operation continuity, and high labor productivity. Moreover, because of the continuous production, the reaction has strong continuity, so that the produced products have strong consistency.

[0044] The following will be further described in combination with specific embodiments:

[0045] Embodiment 1

[0046] A rare earth compound precipitation continuous production method comprises the following steps:

[0047] S1, dilution and activation: the fine crystal slurry, the rare earth solution, and the recycled precipitate wastewater are added to the activation configuration tank through the flow controller, wherein the fine crystal slurry comprises the fine crystal grains in step S5, the addition amount of the fine crystal slurry is 15% of the rare earth tank volume, the concentration of the rare earth ions in the rare earth solution is 1.2 mol / L, and then stirring treatment is performed at a stirring speed of 50 r / min and a reaction temperature of 40℃, so as to obtain a mixed solution, and the concentration of the rare earth ions in the mixed solution is 0.5 mol / L;

[0048] S2, crystal nucleus growth, the mixed solution overflows into a growth precipitation tank, then ammonium carbonate solution is added and stirring treatment is carried out, the stirring speed is 80 r / min, the reaction temperature is 60 DEG C, the slurry pH is 4.8-5.5, and the reaction time is 1 hour, so that crystal nucleus growth slurry is obtained;

[0049] S3, complete crystallization: the crystal nucleus growth slurry overflows into a crystallization precipitation tank, then ammonium carbonate solution is added again and stirring treatment is carried out, the stirring speed is 80 r / min, the reaction temperature is 60 DEG C, the slurry pH is 6.4-6.8, and the reaction time is 0.5 hour, so that completely crystallized slurry is obtained, and the rare earth content in the supernatant of the completely crystallized slurry is less than 0.07 g / L;

[0050] S4, standing and aging: the completely crystallized slurry overflows into an aging precipitation tank, a precipitating agent is added and stirring treatment is carried out, the stirring speed is 20 r / min, the reaction temperature is 40 DEG C, the slurry pH is 6.4-6.8, the aging time is greater than 2 hours, the precipitating agent is one or more of ammonium bicarbonate and ammonia water mixed, and the concentration is 0.5-1.5 mol / L, so that crystalline carbonic acid rare earth material slurry is obtained.

[0051] S5, grading unloading: the crystalline carbonic acid rare earth material slurry overflows into a grading unloading tank, the fine crystal grains in the crystalline carbonic acid rare earth material slurry are led to a crystal slurry transfer tank by rare earth material liquid, and are pumped back to the activation configuration tank; the remaining crystalline carbonic acid rare earth material slurry is pumped to a material slurry transfer tank through an unloading port, and is pumped to a vacuum belt filter for filtration, so that large particle carbonic acid rare earth is obtained.

[0052] Example 2:

[0053] A rare earth compound precipitation continuous preparation method comprises the following steps:

[0054] S1, dilution and activation: fine crystal slurry, rare earth material liquid and recycled precipitation wastewater are added into an activation configuration tank through a flow controller, wherein the fine crystal slurry comprises fine crystal grains in step S5, the addition amount of the fine crystal slurry is 20% of the rare earth tank capacity, the concentration of rare earth ions in the rare earth material liquid is 1.5 mol / L, and then stirring treatment is carried out, the stirring speed is 60 r / min, and the reaction temperature is 40 DEG C, so that a mixed solution is obtained, and the concentration of rare earth ions in the mixed solution is 0.8 mol / L;

[0055] S2, crystal nucleus growth, the mixed solution overflows into a growth precipitation tank, then ammonium carbonate solution is added and stirring treatment is carried out, the stirring speed is 80 r / min, the reaction temperature is 60 DEG C, the slurry pH is 4.8-5.5, and the reaction time is 1 hour, so that crystal nucleus growth slurry is obtained;

[0056] S3, complete crystallization: the slurry is overflowed into a crystallization precipitation tank, ammonium carbonate solution is added again, and stirring treatment is carried out at a stirring speed of 100 r / min, a reaction temperature of 80℃, a slurry pH of 6.4-6.8, and a reaction time of 0.5 hours, so that a completely crystallized slurry is obtained, and the rare earth content in supernatant of the completely crystallized slurry is less than 0.07 g / L;

[0057] S4, standing aging: the completely crystallized slurry is overflowed into an aging precipitation tank, a precipitating agent is added, and stirring treatment is carried out at a stirring speed of 20 r / min, a reaction temperature of 40℃, a slurry pH of 6.4-6.8, and an aging time of more than 3 hours, the precipitating agent is one or more of a mixture of ammonium bicarbonate and ammonia water, and the concentration is 0.5-1.5 mol / L, so that a crystalline carbonic acid rare earth material slurry is obtained.

[0058] S5, grading unloading: the crystalline carbonic acid rare earth material slurry is overflowed into a grading unloading tank, fine crystal grains in the crystalline carbonic acid rare earth material slurry are introduced into a crystal slurry transfer tank by a rare earth material liquid, and are pumped back to an activation configuration tank; the remaining crystalline carbonic acid rare earth material slurry is transported to a material slurry transfer tank through an unloading port, and is pumped to a vacuum belt filter for filtration, so that a large particle carbonic acid rare earth is obtained.

[0059] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for continuously producing a rare earth compound precipitate, characterized by: It comprises the following steps: S1, dilution activation: the fine crystal slurry, rare earth solution and recycled wastewater are added into the activation configuration tank through the flow controller, and then stirring treatment is carried out, so as to obtain a mixed solution; S2, crystal nucleus growth: the mixed solution overflows into the growth precipitation tank, then ammonium carbonate solution is added, and stirring treatment is carried out, so as to obtain crystal nucleus growth slurry; S3, complete crystallization: the crystal nucleus growth slurry overflows into the crystallization precipitation tank, then ammonium carbonate solution is added again, and stirring treatment is carried out, so as to obtain completely crystallized slurry; S4, standing aging: the completely crystallized slurry overflows into the aging precipitation tank, a precipitating agent is added, and stirring treatment is carried out, so as to obtain crystallized rare earth carbonate slurry; S5, grading unloading: the crystallized rare earth carbonate slurry overflows into the grading unloading tank, the fine crystal grains in the crystallized rare earth carbonate slurry are introduced into the crystal slurry transfer tank through the rare earth solution, and are pumped back to the activation configuration tank, the remaining crystallized rare earth carbonate slurry is pumped to the slurry transfer tank through the unloading port, and then is pumped to the vacuum belt filter for filtration, so as to obtain large particle rare earth carbonate; The fine crystal slurry in the step S1 comprises the fine crystal grains in the step S5, and the stirring treatment comprises stirring at a speed of 50-120 r / min and at a temperature of 40-80℃; The stirring treatment in the step S2 comprises stirring at a speed of 50-120 r / min and at a temperature of 40-80℃, the slurry has a pH of 4.8-5.5, and the reaction time is 0.5-1 hour; The stirring treatment in the step S3 comprises stirring at a speed of 50-120 r / min and at a temperature of 40-80℃, the slurry has a pH of 6.4-6.8, the reaction time is 0.5-1 hour, and the supernatant in the completely crystallized slurry has a rare earth content of less than 0.07 g / L; The stirring treatment in the step S4 comprises stirring at a speed of 20-40 r / min and at a temperature of 40-80℃, the slurry has a pH of 6.4-6.8, the aging time is 0.5-1 hour, the precipitating agent is one or more of ammonium bicarbonate and ammonia water, and the concentration is 0.5-1.5 mol / L; The addition amount of the fine crystal slurry in the step S1 is 15%-25% of the rare earth tank volume, the concentration of rare earth ions in the rare earth solution is 1.2-1.8 mol / L, and the concentration of rare earth ions in the mixed solution is 0.2-0.8 mol / L; The activation configuration tank, the growth precipitation tank, the crystallization precipitation tank and the aging precipitation tank are all provided with a pH meter, the growth precipitation tank and the crystallization precipitation tank are both provided with an ammonium carbonate flow meter on one side, and the ammonium carbonate flow meter on one side of the growth precipitation tank and the crystallization precipitation tank is connected with the pH meter inside the growth precipitation tank and the crystallization precipitation tank; The grading unloading tank comprises a grading zone and a discharge zone, the settling rate of the grading zone corresponds to a particle size greater than 80% of the particle size of the crystallized rare earth carbonate slurry, the grading zone comprises a crystal slurry transfer tank, and the discharge zone comprises a slurry transfer tank.

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