Method and process for preparing MHP by controlling crystallization in hydrometallurgy of laterite nickel ore

Abstract

The present application belongs to the technical field of hydrometallurgy of laterite nickel ore. Provided are a method and process for preparing MHP by controlling crystallization in hydrometallurgy of laterite nickel ore. The method comprises: on the basis of a nucleation reaction condition, determining the crystal nucleus quantity of a plurality of crystal nuclei after an iron-aluminum-removed liquid has undergone a nucleation reaction; on the basis of a primary growth reaction condition, determining an average particle size of a plurality of grains after the plurality of crystal nuclei have undergone primary growth; and, on the basis of Metropolis algorithm, the crystal nucleus quantity, and the average particle size, determining a predicted particle size distribution of agglomerated grains after the plurality of grains have undergone secondary agglomeration and growth. On the basis of a predicted particle size distribution result, the present application can adjust the reaction conditions of the nucleation reaction and the primary growth reaction to control the crystal nucleus quantity and the average particle size, so as to obtain high-performance MHP products with better particle size distribution, thereby having a guiding effect on crystallization processes of MHP.

Description

Method and process for preparing MHP by controlling crystallization in laterite nickel ore hydrometallurgy TECHNICAL FIELD

[0001] The present application relates to the technical field of laterite nickel ore hydrometallurgy, in particular to a method and process for preparing MHP by controlling crystallization in laterite nickel ore hydrometallurgy. BACKGROUND

[0002] Nickel cobalt manganese hydroxide (MHP) is an intermediate product of nickel prepared by high-pressure acid leaching technology using laterite nickel ore as raw material. Nickel cobalt manganese hydroxide can be used to produce nickel sulfate, refined nickel cobalt manganese hydroxide, nickel plate and other products, especially to produce nickel sulfate as one of the main materials for ternary battery cathode materials. In recent years, with the continuous development of electric vehicles and other industries, the market capacity of ternary batteries continues to expand, which also promotes the market demand for nickel cobalt manganese hydroxide.

[0003] The preparation process of nickel cobalt manganese hydroxide is: adding a precipitating agent to the iron and aluminum removed liquid to nucleate, grow primary crystal grains, and agglomerate and grow secondary crystal grains of nickel cobalt manganese hydroxide in the iron and aluminum removed liquid, and finally obtain nickel cobalt manganese hydroxide. The particle size distribution of the agglomerated grains obtained after the secondary crystal grains of nickel cobalt manganese hydroxide agglomerate and grow has a great influence on the performance of nickel cobalt manganese hydroxide. The existing technology evaluates the particle size distribution of the actually obtained agglomerated particles to determine the performance of the agglomerated particles, but cannot predict the particle size distribution of the agglomerated grains, that is, cannot optimize the reaction conditions before preparation to make the particle size distribution meet the requirements, resulting in the technical problem that the performance of the prepared nickel cobalt manganese hydroxide is uncontrollable. In the actual production process, the ideal MHP product should have a relatively narrow particle size distribution range and uniform morphology. Such a precipitated product has a high settling rate, a fast filtration speed, and a low moisture content of the filter cake.

[0004] Therefore, it is necessary to provide a method and process for preparing MHP by controlling crystallization in laterite nickel ore hydrometallurgy, which can accurately predict the particle size distribution of the agglomerated grains to make the MHP product have a relatively narrow particle size distribution, thereby improving the performance of the prepared nickel cobalt manganese hydroxide.

[0005] SUMMARY

[0006] Therefore, it is necessary to provide a method and process for preparing MHP by controlling crystallization in laterite nickel ore hydrometallurgy, which can accurately predict the particle size distribution of the agglomerated grains to make the MHP product have a relatively narrow particle size distribution, thereby improving the performance of the prepared nickel cobalt manganese hydroxide.

[0007] On the one hand, in order to solve the above technical problems, the present application provides a method for preparing MHP by controlling crystallization in laterite nickel ore hydrometallurgy, comprising:

[0008] determine a number of crystal nuclei of a plurality of crystal nuclei after the iron and aluminum removed solution undergoes the nucleation reaction based on the nucleation reaction condition;

[0009] determine an average grain size of a plurality of crystal grains after the plurality of crystal nuclei undergoes primary growth based on the primary growth reaction condition;

[0010] determine a predicted grain size distribution of agglomerated crystal grains after the plurality of crystal grains undergoes secondary agglomeration and growth based on the Metropolis algorithm, the number of crystal nuclei and the average grain size.

[0011] In a possible implementation, the nucleation reaction condition includes pH and mass of a precipitant; and the determining the number of crystal nuclei of the plurality of crystal nuclei after the iron and aluminum removed solution undergoes the nucleation reaction based on the nucleation reaction condition includes:

[0012] determine a supersaturation of the primary nickel-cobalt-manganese hydroxide precipitate solution based on the pH and the mass of the precipitant;

[0013] determine a crystallization rate of the primary nickel-cobalt-manganese hydroxide precipitate solution based on the supersaturation and a crystallization rate model;

[0014] determine the number of crystal nuclei of the plurality of crystal nuclei based on the crystallization rate.

[0015] In a possible implementation, the crystallization rate model is:

[0016] J0=A·ln S

[0017] wherein, J is the crystallization rate, 1 / (m 3 ·s); J0 is the maximum crystallization rate, 1 / (m 3 ·s); γ is the surface energy of the hydroxide precipitate, J / m 2 ; is the partial molar volume of the hydroxide, mol / m 3 ; k B is the Boltzmann constant; R g is the ideal gas constant, J / (mol·K); T is the temperature, K; S is the supersaturation; A is the proportional constant; is the concentration of divalent ions in the iron and aluminum removed solution; c OH is the concentration of hydroxyl ions; is the solubility product of the hydroxide precipitate; N A is the Avogadro constant; is the diffusion rate constant of the M 2+ metal ion in the solution.

[0018] In a possible implementation, the determining the average grain size of the plurality of grains after one-time growth of the plurality of crystal nuclei based on the one-time growth reaction condition comprises:

[0019] determining a hydroxide precipitate concentration in the one-time growth process of the crystal nuclei based on the one-time growth reaction condition;

[0020] determining the average grain size of the plurality of grains based on the hydroxide precipitate concentration, a grain growth partial differential equation and a boundary condition.

[0021] In a possible implementation, the grain growth partial differential equation is:

[0022] The boundary condition is:

[0023] In the formula, is the concentration of the hydroxide precipitate after the one-time growth reaction condition; D is a diffusion rate constant of the hydroxide precipitate in the solution; r is a vector position, t is time, c(r, t) is a composition field variable; and R is a vector field maximum position. is the concentration of the hydroxide precipitate in the solution phase.

[0024] In a possible implementation, the determining the predicted grain size distribution of the agglomerated grains based on the Metropolis algorithm, the number of crystal nuclei and the average grain size comprises:

[0025] Step one, taking the number of crystal nuclei and the average grain size as an initial state;

[0026] Step two, exchanging liquid and grain positions in the secondary agglomeration and growth of the nickel-cobalt-manganese hydroxide precipitate solution;

[0027] Step three, determining the total energy of the nickel-cobalt-manganese hydroxide precipitate solution after the exchange of the liquid and grain positions;

[0028] Step four, determining a change trend of the total energy, accepting the position change when the change trend is decreasing, and accepting the position change with a preset probability when the change trend is increasing;

[0029] Step five, returning to step two and repeatedly performing steps two to four until the number of position changes reaches a preset iteration number, and taking the liquid and crystal positions in the last time as target positions;

[0030] Step six, determining the predicted grain size distribution of the agglomerated grains based on the target positions.

[0031] In a possible implementation, the total energy comprises agglomeration energy and stirring energy.

[0032] In a possible implementation, the maximum distance between the exchanged liquid and the crystal grains satisfies:

[0033] where Δx is the maximum distance; D is the diffusion rate of the crystal grains, m / s; and Δt is the time interval between two successive iterative calculations. max p 2 where Δx is the maximum distance; D is the diffusion rate of the crystal grains, m / s; and Δt is the time interval between two successive iterative calculations.

[0034] In a possible implementation, the method further includes:

[0035] When the predicted particle size distribution does not satisfy the expected particle size distribution, the nucleation reaction condition and / or the primary growth reaction condition are optimized until the predicted particle size distribution satisfies the expected particle size distribution.

[0036] In another aspect, the application also provides a process for preparing MHP by laterite nickel ore hydrometallurgy controlled crystallization, based on the method for preparing MHP by laterite nickel ore hydrometallurgy controlled crystallization.

[0037] The method for preparing MHP by laterite nickel ore hydrometallurgy controlled crystallization is any of the methods for preparing MHP by laterite nickel ore hydrometallurgy controlled crystallization described above.

[0038] The method for preparing MHP by laterite nickel ore hydrometallurgy controlled crystallization provided by the application first determines the number of crystal nuclei after the iron and aluminum removal liquid undergoes nucleation reaction based on the nucleation reaction condition, and then determines the average particle size of the crystal grains after the crystal nuclei undergo primary growth based on the primary growth reaction condition. The number of crystal nuclei and the average particle size are used as the prerequisite parameters of the predicted particle size distribution, which can improve the accuracy of the determined predicted particle size distribution.

[0039] Further, since the secondary agglomeration and growth of the crystal grains are random, the application determines the predicted particle size distribution based on the Metropolis algorithm, which can simulate the characteristics of random sampling distribution and achieve the purpose of accurately describing the secondary agglomeration and growth process of the crystal grains, further improving the accuracy of the predicted particle size distribution.

[0040] According to the predicted particle size distribution result, the application adjusts the reaction conditions of the nucleation reaction and the primary growth reaction to control the number of crystal nuclei and the average particle size, so as to obtain high-performance MHP products with better particle size distribution, which has a guiding role for the crystallization process of MHP. BRIEF DESCRIPTION OF DRAWINGS

[0041] ​​In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0042] Fig. 1 is a schematic diagram of an embodiment of the method for preparing MHP by controlling crystallization of laterite nickel ore by hydrometallurgy provided by the present application;

[0043] Fig. 2 is a schematic diagram of an embodiment of S101 in Fig. 1 of the present application;

[0044] Fig. 3 is a schematic diagram of an embodiment of S102 in Fig. 1 of the present application;

[0045] Fig. 4 is a schematic diagram of an embodiment of S103 in Fig. 1 of the present application;

[0046] Fig. 5 is a schematic diagram of the predicted particle size distribution corresponding to different pH values of the precipitants provided by the present application;

[0047] Fig. 6 is a comparison diagram before and after the optimization of the particle size distribution provided by the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0049] It should be understood that the schematic drawings are not drawn to scale. The flowcharts in the present application show the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowcharts can be implemented in no order, the steps without logical context relationship can be reversed in order or implemented simultaneously. In addition, one or more other operations can be added to the flowcharts or removed from the flowcharts by those skilled in the art under the guidance of the content of the present application. Some block diagrams shown in the drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor systems and / or microcontroller systems.

[0050] Reference to“an embodiment” herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be incorporated into other embodiments.

[0051] The application provides a method and process for preparing MHP by hydrometallurgical controlled crystallization of laterite nickel ore.

[0052] FIG. 1 is a flowchart of an embodiment of the method for preparing MHP by hydrometallurgical controlled crystallization of laterite nickel ore provided by the application. As shown in FIG. 1, the method for preparing MHP by hydrometallurgical controlled crystallization of laterite nickel ore includes:

[0053] S101, determining the number of crystal nuclei of a plurality of crystal nuclei after the post-iron and aluminum removal solution undergoes a nucleation reaction based on nucleation reaction conditions;

[0054] S102, determining the average particle size of a plurality of crystal grains after the plurality of crystal nuclei undergoes primary growth based on primary growth reaction conditions;

[0055] S103, determining the predicted particle size distribution of the agglomerated crystal grains after the plurality of crystal grains undergoes secondary agglomeration and growth based on the Metropolis algorithm, the number of crystal nuclei, and the average particle size.

[0056] In step S101, the post-iron and aluminum removal solution is a solution obtained after high-pressure acid leaching and iron and aluminum removal treatment of laterite nickel ore.

[0057] It should be noted that both the nucleation reaction and the primary growth reaction are adding a precipitator to the solution, and based on the precipitator added, the crystal seeds in the solution undergo a precipitation reaction to achieve crystal nucleus generation and crystal grain growth.

[0058] It should be understood that the precipitator is at least one of sodium hydroxide, lime milk, potassium hydroxide, calcium oxide, magnesium oxide, and magnesium hydroxide.

[0059] Compared with the prior art, the method for preparing MHP by hydrometallurgical controlled crystallization of laterite nickel ore provided by the embodiments of the application first determines the number of crystal nuclei of a plurality of crystal nuclei after the post-iron and aluminum removal solution undergoes a nucleation reaction based on nucleation reaction conditions, and then determines the average particle size of a plurality of crystal grains after the plurality of crystal nuclei undergoes primary growth based on primary growth reaction conditions. The number of crystal nuclei and the average particle size are used as prerequisite parameters of the predicted particle size distribution, which can improve the accuracy of the predicted particle size distribution determined.

[0060] Further, since secondary agglomeration and growth of the crystal grains have randomness, the application determines the predicted particle size distribution based on the Metropolis algorithm, uses the characteristic of simulating random sampling distribution, realizes the purpose of accurately describing the secondary agglomeration and growth process of the crystal grains, and further improves the accuracy of the predicted particle size distribution.

[0061] In some embodiments of the application, the nucleation reaction condition and the primary growth reaction condition include at least one parameter affecting nucleation and primary growth, for example, including a precipitant parameter, and / or, a post-iron and aluminum removal solution parameter, the precipitant parameter including mass and pH of the precipitant, and the post-iron and aluminum removal solution parameter including mass and concentration of the post-iron and aluminum removal solution.

[0062] In specific embodiments of the application, the nucleation reaction condition includes the pH and mass of the precipitant; and as shown in FIG. 2, the step S101 includes:

[0063] S201, determining the supersaturation of the primary nickel-cobalt-manganese hydroxide precipitation solution based on the pH and mass of the precipitant;

[0064] S202, determining the crystallization rate of the primary nickel-cobalt-manganese hydroxide precipitation solution based on the supersaturation and the crystallization rate model;

[0065] S203, determining the number of crystal nuclei of the plurality of crystal nuclei based on the crystallization rate.

[0066] The embodiments of the application determine the crystallization rate by using the effective and accurate crystallization rate model, accurately describe the crystallization mechanism, and improve the accuracy of the determined number of crystal nuclei.

[0067] wherein the calculation formula of the supersaturation S is:

[0068] In the formula, c is the concentration of divalent ions in the post-iron and aluminum removal solution; c OH is the concentration of hydroxyl ions; is the solubility product of the hydroxide precipitate.

[0069] In specific embodiments of the application, the crystallization rate model is:

[0070] J0=A·ln S

[0071] In the formula, J is the crystallization rate, 1 / (m 3 ·s); J0 is the maximum crystallization rate, 1 / (m 3 ·s); γ is the surface energy of the hydroxide precipitate, J / m 2 . V is the partial molar volume of the hydroxide, mol / m 3 ; k B is the Boltzmann constant; R g is the ideal gas constant, J / (mol·K); T is the temperature, K; N A is the Avogadro constant; M 2+ is the diffusion rate constant of the metal ion in the solution.

[0072] It should be noted that: step S203 specifically is: based on the crystallization rate, the crystallization time and the volume of the iron and aluminum removed liquid, the number of crystal nuclei can be determined.

[0073] In some embodiments of the present application, as shown in FIG. 3, step S102 includes:

[0074] S301, determining the hydroxide precipitate concentration in the crystal nucleus one-time growth process based on the one-time growth reaction condition;

[0075] S302, determining the average particle size of the plurality of crystal grains based on the hydroxide precipitate concentration, the crystal grain growth partial differential equation and the boundary condition.

[0076] The embodiments of the present application determine the influence parameters of the one-time growth reaction condition on the crystal nucleus one-time growth process, and then determine the average particle size of the plurality of crystal grains generated after the one-time growth reaction based on the influence parameters, which can ensure the accuracy of the average particle size under the one-time growth reaction condition.

[0077] In specific embodiments of the present application, the crystal grain growth partial differential equation is:

[0078] The boundary condition is:

[0079] In the formula, M is the concentration of the hydroxide precipitate after the one-time growth reaction condition; D is the diffusion rate constant of the hydroxide precipitate in the solution; r is the vector position, t is the time, c(r, t) is the composition field variable; R is the maximum position of the vector field; M is the concentration of the hydroxide precipitate in the solution.

[0080] Since the case of global energy minimum is considered as the most stable case of secondary agglomeration and growth, i.e., the optimal possible particle size distribution, in some embodiments of the present application, as shown in FIG. 4, step S103 includes:

[0081] S401, taking the number of crystal nuclei and the average particle size as the initial state;

[0082] S402, exchange the liquid and the grain position in the nickel-cobalt-manganese hydroxide precipitation solution in the secondary agglomeration and growth;

[0083] S403, determine the total energy of the nickel-cobalt-manganese hydroxide precipitation solution after the liquid and the grain position are exchanged;

[0084] S404, determine the change trend of the total energy, when the change trend is variable, accept the position change, and when the change trend is variable, accept the position change with a preset probability;

[0085] S405, return to step S402, and repeat steps S402-S404 until the position change times reach a preset iteration number, and the last liquid and crystal position is taken as the target position;

[0086] S406, determine the predicted particle size distribution of the agglomerated grain based on the target position.

[0087] The embodiments of the present application are configured to accept the position change when the change trend is variable, and accept the position change with a preset probability when the change trend is variable, so that the process of predicting the particle size distribution is prevented from falling into a local minimum value, and the accuracy of the predicted particle size distribution is further improved.

[0088] In some embodiments of the present application, the total energy is the energy between the solid and the liquid, and the energy between the solid and the liquid includes agglomeration energy and stirring energy. Specifically, the total energy is:

[0089] E agglo =4π(R i (t)) 2 ·γ

[0090] E agi =-A f ·Ω

[0091] In the formula, ε sl is the total energy; E agglo is the agglomeration energy; E agi is the stirring energy; R i (t) is the particle size of the secondary agglomerated particle at t, m; γ is the surface energy density, mJ / m 2 ; A f is the proportional coefficient; Ω is the stirring speed, Hz.

[0092] It should be noted that the distance between the liquid and the grain position should not be too far when they are exchanged in step S402, and the maximum distance satisfies:

[0093]

[0094] In the formula, Δx maxDmax is the maximum distance; D p D is the diffusion rate of the crystal grains, m 2 / s; Δt is the time interval between two consecutive iterative calculations.

[0095] The embodiments of the present application constrain the distance between the liquid and the crystal grain position exchange, so that the process is more in line with the process of secondary agglomeration and growth of the crystal grains, thereby further ensuring the accuracy of the predicted particle size distribution obtained.

[0096] To achieve quality control of the finally obtained nickel-cobalt-manganese hydroxide product, in some embodiments of the present application, after step S103, further comprising:

[0097] When the predicted particle size distribution does not meet the expected particle size distribution, the nucleation reaction conditions and / or the primary growth reaction conditions are optimized until the predicted particle size distribution meets the expected particle size distribution.

[0098] Through optimization of the nucleation reaction conditions and / or the primary growth reaction conditions, the predicted particle size distribution obtained can meet the expected particle size distribution, thereby achieving control of the preparation of MHP by controlled crystallization of laterite nickel ore hydrometallurgy, and improving the quality of the MHP product obtained.

[0099] In one specific embodiment of the present application, FIG. 5 is the predicted particle size distribution obtained when the pH of the precipitant is 9.0 and 12.0, respectively. As can be seen from FIG. 5, the higher the pH of the solution during precipitation, the smaller the average particle size of the final product, which is more conducive to subsequent pressure filtration treatment. After adjusting the process conditions of actual production according to the calculation results, the particle size distribution of the MHP product obtained is shown in FIG. 6. As can be seen from FIG. 6, the MHP particle size distribution curve after process optimization is significantly narrower, and the particle size is overall smaller, which is consistent with the calculation and prediction results, verifying the feasibility of the method.

[0100] The embodiments of the present application also provide a process for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy, which is based on the method for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy.

[0101] The method for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy is any one of the methods for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy described above.

[0102] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiments can be completed by a computer program instructing relevant hardware (such as a processor, a controller, etc.) to complete, and the computer program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory, or a random access memory, etc.

[0103] The method and process for preparing MHP by controlling crystallization of laterite nickel ore by hydrometallurgy provided by the present application are described in detail above, and the principles and implementation modes of the present application are described by using specific examples. The above examples are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, there will be changes in the specific implementation modes and application ranges according to the idea of the present application. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method for the preparation of MHP by hydrometallurgical controlled crystallization of laterite nickel ores, characterized in that, The method comprises the following steps: determining the number of crystal nuclei of a plurality of crystal nuclei after nucleation reaction of the iron-removed and aluminum-removed solution based on nucleation reaction conditions; determining the average grain size of a plurality of crystal grains after primary growth of the plurality of crystal nuclei based on primary growth reaction conditions; determining the predicted grain size distribution of the agglomerated crystal grains after secondary agglomeration and growth of the plurality of crystal grains based on the Metropolis algorithm, the number of crystal nuclei and the average grain size.

2. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 1, characterized in that, The nucleation reaction conditions include the pH value and mass of the precipitant, and the number of crystal nuclei of the plurality of crystal nuclei after nucleation reaction of the iron-removed and aluminum-removed solution is determined based on the pH value and mass of the precipitant, comprising the following steps: determining the supersaturation of the primary nickel-cobalt-manganese hydroxide precipitate solution based on the pH value and mass of the precipitant; determining the crystallization rate of the primary nickel-cobalt-manganese hydroxide precipitate solution based on the supersaturation and a crystallization rate model; determining the number of crystal nuclei of the plurality of crystal nuclei based on the crystallization rate.

3. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 2, characterized in that, The crystallization rate model is: J0 = A - ln S where J is the crystallization rate, 1 / (m 3 ·s); J0is the maximum crystallization rate, 1 / (m 3 ·s); γ is the surface energy of the hydroxide precipitate, J / m 2 ; V is the partial molar volume of the hydroxide, mol / m 3 ; k B R is the Boltzmann constant; R g R is the ideal gas constant, J / (mol-K); T is the temperature, K; S is the supersaturation; A is a proportionality constant; to reduce the concentration of divalent ions in the iron and aluminum removed solution; c OH to reduce the concentration of hydroxide ions; Ksp is the solubility product of the hydroxide precipitate; N A N is Avogadro's number; M 2+ Diffusion rate constant of metal ions in solution.

4. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 1, characterized by that, The average grain size of the plurality of crystal grains after primary growth of the plurality of crystal nuclei is determined based on the primary growth reaction conditions, comprising the following steps: determining the hydroxide precipitate concentration in the process of primary growth of the crystal nuclei based on the primary growth reaction conditions; determining the average grain size of the plurality of crystal grains based on the hydroxide precipitate concentration, a grain growth partial differential equation and boundary conditions.

5. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 4, characterized in that, The grain growth partial differential equation is: The boundary conditions are: In the formulae, C is the concentration of the hydroxide precipitate in the solution bulk phase. The diffusion rate constant of the precipitated substance in the solution; r is the vector position, t is the time, c(r, t) is the composition field variable; R is the vector field maximum position; C is the concentration of the hydroxide precipitate in the solution bulk phase.

6. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 1, characterized in that, The predicted grain size distribution of the agglomerated crystal grains is determined based on the Metropolis algorithm, the number of crystal nuclei and the average grain size, comprising the following steps: Step 1: taking the number of crystal nuclei and the average grain size as initial states; Step 2: exchanging the positions of the liquid and the crystal grains in the secondary agglomeration and growth of the nickel-cobalt-manganese hydroxide precipitate solution; Step 3: determining the total energy of the nickel-cobalt-manganese hydroxide precipitate solution after the position exchange of the liquid and the crystal grains; Step 4: determining the change trend of the total energy, accepting the position change when the change trend is decreasing, and accepting the position change with a preset probability when the change trend is increasing; Step 5: returning to Step 2 and repeatedly executing Steps 2-4 until the number of position changes reaches a preset iteration number, and taking the positions of the liquid and the crystal grains in the last time as target positions; Step 6: determining the predicted grain size distribution of the agglomerated crystal grains based on the target positions.

7. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 6, characterized in that, The total energy includes agglomeration energy and stirring energy.

8. The method of controlled crystallization of nickel laterite hydrometallurgical preparation of MHP according to claim 6, characterized in that, The maximum distance between the liquid and the crystal grain at the exchange location satisfies: where Δx max is the maximum distance; D p is the diffusion rate of the crystal grains, m 2 / s; and Δt is the time interval between two successive iterative calculations.

9. The method of controlling crystallization in hydrometallurgical processing of nickel laterite ores to produce MHP according to claim 1, characterized in that, The method further comprises the following steps: when the predicted grain size distribution does not satisfy an expected grain size distribution, optimizing the nucleation reaction conditions and / or the primary growth reaction conditions until the predicted grain size distribution satisfies the expected grain size distribution.

10. A process for the preparation of MHP by hydrometallurgical controlled crystallization of laterite nickel ores, characterized in that, The method is realized based on the method for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy; The method for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy is the method for preparing MHP by controlled crystallization of laterite nickel ore hydrometallurgy according to any one of claims 1-9.

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