A method for optimizing calculation of sodium fluorosilicate production

Abstract

The application discloses a kind of sodium fluorosilicate production optimization calculation method, the surface energy of different crystal faces of sodium fluorosilicate is calculated, and the minimum crystal face is selected;For the minimum crystal face of the surface energy, preset the surface of electronic density is used to draw and display surface electrostatic potential and calculate energy;Obtain a preset number of impurity ions, calculate the energy of the preset number of fluorine ions in the minimum crystal face of the surface energy replaced by the impurity ions, and output the energy difference after replacement according to the calculated energy.The application calculates the surface energy of different crystal faces of sodium fluorosilicate, selects the minimum crystal face of the surface energy as the leading crystal face and carries out subsequent calculation.Then, the energy change of the fluorine ion in sodium fluorosilicate replaced by impurity ion is calculated, the binding energy of impurity ion and sodium fluorosilicate leading crystal face is shown by calculation result, the energy change of crystal surface energy and crystal growth caused by impurity ion is given, and the influence of impurity on sodium fluorosilicate production can be accurately judged according to the energy.

Description

Technical Field

[0001] This invention relates to the field of chemical calculations, and in particular to an optimization calculation method for sodium fluorosilicate production. Background Technology

[0002] Industrially, sodium fluorosilicate is mainly produced using a byproduct of phosphate fertilizer production, supplemented by chemical neutralization / metathesis methods. The core processes are as follows:

[0003] 1. Superphosphate by-product method (mainstream process): When phosphate rock powder reacts with sulfuric acid to produce superphosphate / extracted phosphoric acid, the fluorine-containing waste gas that escapes is absorbed by water to generate fluorosilicic acid with a concentration of 8%~10%. An excess of about 25% sodium chloride is added to the clarified fluorosilicic acid, and sodium fluorosilicate is generated through a metathesis reaction. The finished product is then obtained by centrifugation, washing, air drying at a temperature below 300°C, and pulverization.

[0004] 2. Neutralization / Metathesis Method: This method involves directly neutralizing sodium carbonate (or sodium hydroxide) with fluorosilicic acid, or performing a metathesis reaction between sodium chloride (sodium salt) and fluorosilicic acid. This is an auxiliary process.

[0005] 3. Wet-process phosphoric acid by-product method: Relying on the co-production of the phosphate fertilizer industry chain, using fluorosilicic acid, a by-product of wet-process phosphoric acid, as raw material, and producing it through precipitation method, it is one of the core preparation routes for industrial-grade sodium fluorosilicate.

[0006] The core problem with existing preparation methods is that the raw material fluorosilicic acid contains impurities such as nitrates and sulfates, which are easily adsorbed onto the crystal surface during crystal growth. Furthermore, traditional processes cannot predict the impact of impurities on sodium fluorosilicate production, leading to fluctuations in product purity and excessive impurity content. Summary of the Invention

[0007] Therefore, there is a need to provide an optimization calculation method for sodium fluorosilicate production to solve the problem that traditional processes cannot predict the impact of impurities on sodium fluorosilicate production.

[0008] To achieve the above objectives, the present invention provides an optimization calculation method for sodium fluorosilicate production, comprising the following steps:

[0009] The crystal plane energy of sodium fluorosilicate at different crystal planes is calculated using the following formula:

[0010]

[0011] For crystal plane energy, It is the total energy of the relaxed slab model, that is, the energy of the system after the sodium fluorosilicate material is cut out of the surface; It is the energy of the bulk phase, that is, the energy of the complete bulk before cutting the slab model; n is the surface area of ​​the crystal plane; n is the number of bulk units.

[0012] Select the crystal plane with the minimum crystal energy;

[0013] For the crystal plane with the minimum crystal energy, the surface electrostatic potential is plotted and displayed using a preset electron density isosurface, and the energy is calculated.

[0014] Obtain a preset number of impurity ions, calculate the energy required for the impurity ions to replace a preset number of fluorine ions in the crystal plane with the minimum crystal energy, calculate the energy difference after replacement based on the calculated energy, and output the result. The formula for calculating the energy difference is as follows:

[0015]

[0016] in, The energy difference between the models;

[0017] The total energy of the crystal plane composite system after the replacement of the pre-defined impurity ions;

[0018] To replace the total energy of the fluoride ion crystal plane system;

[0019] The reference energy for a single preset impurity ion;

[0020] The reference energy for a single replaced fluoride ion;

[0021] m is the preset number of impurity ions, and it is the same as the number of fluorine ions being replaced.

[0022] Furthermore, the impurity ions include nitrate ions.

[0023] Furthermore, the preset quantity is 2.

[0024] Furthermore, the preset quantity is 0.001au.

[0025] Furthermore, the energy calculation process involves calling the VASP software package, the interaction between atoms and electrons is described using the projection-enhanced wave method, the electron wave function is expanded using a plane wave basis set, and the cutoff energy of the plane wave is adjusted according to a preset precision.

[0026] Unlike existing technologies, the above-mentioned technical solution calculates the crystal plane energy of different crystal planes of sodium fluorosilicate, selects the crystal plane with the lowest crystal plane energy as the dominant crystal plane, and performs subsequent calculations. Then, it calculates the energy change of impurity ions replacing fluoride ions in sodium fluorosilicate. The calculation results demonstrate the binding energy between impurity ions and the dominant crystal plane of sodium fluorosilicate, and provide the energy changes of impurity ions on crystal plane energy and crystal growth. Based on this energy, the impact of impurities on sodium fluorosilicate production can be accurately determined. This overcomes the problems of traditional processes being unable to predict impurity adsorption behavior and difficult to control the impact of impurities, providing a quantitative basis for raw material impurity removal and process parameter optimization. Attached Figure Description

[0027] Figure 1 This is a surface electrostatic potential diagram of sodium fluorosilicate according to the present invention;

[0028] Figure 2 This is an energy diagram of the sodium fluorosilicate crystal plane before nitrate impurity ion substitution in this invention.

[0029] Figure 3 This is a crystal structure model diagram of sodium fluorosilicate before nitrate impurity ion substitution in this invention;

[0030] Figure 4 This is a crystal structure model diagram of sodium fluorosilicate after nitrate impurity ion substitution in this invention;

[0031] Figure 5 This is a surface electrostatic potential diagram of sodium fluorosilicate after nitrate impurity ion substitution in this invention.

[0032] Figure 6 This is an energy diagram of the sodium fluorosilicate crystal plane after nitrate impurity ion substitution in this invention. Detailed Implementation

[0033] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0034] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0035] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0036] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0037] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0038] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0039] Similar to the interpretation in the Patent Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also interpreted in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0040] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0041] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0042] Please see Figures 1 to 6 This invention provides a computational method for optimizing sodium fluorosilicate production. It employs density functional theory (DFT) for material structure optimization and electronic property calculations, using the VASP (Vienna Ab-initio Simulation Package) software. Atom-electron interactions are described using the projection-enhanced wave (PAW) method, with the electronic wavefunction expanded using a plane-wave basis set. The cutoff energy of the plane waves is adjusted according to the required accuracy to ensure accurate calculations of electronic structure and surface energy. The exchange-correlation effect is addressed using the PBE (Perdew-Burke-Ernzerhof) functional from the generalized gradient approximation (GGA), widely used in structure optimization and electronic structure calculations, effectively balancing computational accuracy and efficiency.

[0043] In processing the electronic wavefunction, a plane-wave basis set expansion is used, and the PAW method replaces the traditional pseudopotential method to improve computational accuracy, especially in describing electron density and total energy. An appropriate PAW pseudopotential is chosen to describe the interaction between the ion nucleus and outer electrons, thereby simplifying calculations, reducing computational complexity, and improving efficiency. The cutoff energy is set to an appropriate value to ensure computational accuracy and wavefunction convergence.

[0044] In electronic structure calculations, the K-point sampling method is used to handle periodic boundary conditions, and an appropriate K-point grid density is selected to ensure the accuracy of the calculation results. The density of the K-point grid is optimized based on the symmetry of the system and the computational requirements. Electronic optimization employs the self-consistent field (SCF) method, iteratively adjusting the electron density and wavefunction until energy convergence. Ion optimization uses the conjugate gradient (CG) algorithm to ensure that the total energy of the system reaches a minimum.

[0045] In one specific embodiment, the method of the present invention includes the following steps: calculating the crystal plane energy of different crystal planes of sodium fluorosilicate, wherein the crystal plane energy formula is as follows:

[0046]

[0047] For crystal plane energy, It is the total energy of the relaxed slab model, that is, the energy of the system after the sodium fluorosilicate material is cut out of the surface; It is the energy of the bulk phase, that is, the energy of the complete bulk before cutting the slab model; is the surface area of ​​the crystal plane; n is the number of bulk units, which can be 1. The slab model simulates the material surface using a finite layer of atoms and a vacuum layer. Relaxation refers to the process of optimizing the surface atomic structure to eliminate unreasonable atomic arrangements and bring the surface atoms to their lowest energy state when calculating surface energy.

[0048] This embodiment calculates the energies of three typical crystal planes of sodium fluorosilicate crystals, and the results are shown in Table 1 below:

[0049] Table 1: Three typical crystal plane energies of sodium fluorosilicate crystals

[0050]

[0051] Based on surface energy calculations, the surface energies of the (0001), (1-100), and (10-10) crystal planes are 0.0765, 0.1278, and 0.2091 eV·Å, respectively. -2 Among them, the 0001 crystal plane has the lowest surface energy, indicating that it is the most thermodynamically stable and is usually the dominant crystal plane that is preferentially grown and exposed over a large area during crystal growth.

[0052] (1-100) The crystal facet is a typical facet of a hexagonal crystal. Its surface energy is at a medium level, indicating that the crystal facet has a certain stability during crystal growth and may form the main epitaxial morphology of the crystal together with the 0001 crystal facet.

[0053] In comparison, the (10-10) crystal plane has the highest surface energy (0.2091 eV·Å). -2 This indicates that it has the worst thermodynamic stability, is prone to surface reconstruction, atomic rearrangement or being replaced by other low-energy crystal planes, and is not easily exposed in large areas in equilibrium crystal form, but exists more in the form of secondary crystal planes.

[0054] In summary, it can be inferred that the 0001 crystal face, as the top face of a hexagonal crystal, occupies a dominant position in the equilibrium crystal form; the (1-100) crystal face, as an edge face, has secondary stability; while the (10-10) crystal face, due to its high surface energy, is not easily exposed during the crystal growth process.

[0055] The effect of surface electrostatic potential on adsorption was then calculated: changes in surface potential may alter the adsorption behavior of ions or molecules on the crystal surface. The introduction of nitrate ions may affect the distribution of adsorbed ions and the rate of surface reactions, thereby affecting morphology growth.

[0056] Then, the crystal plane with the lowest crystal energy is selected; for the crystal plane with the lowest crystal energy, the surface electrostatic potential is plotted and displayed using a preset electron density isosurface, and the energy is calculated; such as Figure 1 and Figure 2 As shown. An isosurface with an electron density of 0.001 au (atomic units) is used for plotting here. A commonly used standard electron density isosurface is selected here; in other embodiments, adjustments can be made according to actual circumstances. Figure 1 In this crystal, the blue color surrounding fluoride ions on the crystal surface indicates a negative electrostatic potential in these regions; the deeper the blue, the stronger the negative polarity. Sodium ions, on the other hand, appear red, indicating a positive electrostatic potential; similarly, the deeper the red, the stronger the positive polarity. Figure 2 In the graph, the horizontal axis represents the distance between atoms, and the vertical axis represents the total energy of the system. The plateau on the curve represents the vacuum energy level of 3.11 eV, indicating the energy required for an electron to remain stable after escaping from the material. Note: Plane wave calculations discard the G=0 region when dealing with electrostatic interactions, causing a shift in energy levels. Therefore, the absolute value of the calculated electrostatic potential is not meaningful (for surface systems, we can usually refer to the region far from the surface as the energy zero point to determine the relative value of the electrostatic potential).

[0057] Obtain a preset number of impurity ions (here, two nitrate ions are used as an example; the specific number can be determined based on the concentration and type of impurity ions in actual production). The crystal models before and after replacement are as follows: Figure 3 and Figure 4 As shown. The surface electrostatic potential diagram and energy diagram after nitrate substitution are as follows. Figure 5 and Figure 6 As shown, the vacuum energy level is 3.43 eV. Then, the energy required for the impurity ions to replace a predetermined number of fluorine ions in the crystal plane with the minimum energy is calculated. Based on the calculated energy, the energy difference after replacement is calculated and output. The formula for calculating the energy difference is as follows:

[0058]

[0059] in:

[0060] The model energy difference of the replacement model is calculated using the following formula:

[0061] in:

[0062] The energy difference between the models;

[0063] The total energy of the surface composite system after impurity ion replacement;

[0064] This represents the total energy of the system before replacing the target crystal plane;

[0065] This is the reference energy for a single impurity ion, in the example, for the nitrate ion;

[0066] The reference energy for a single replaced fluoride ion;

[0067] m represents the number of impurity ions, which is the same as the number of fluorine ions being replaced.

[0068] The reference energy is the total energy of the corresponding ion under a preset reference calculation model.

[0069] In this embodiment, m=2, and the energy parameters can be obtained from the corresponding calculation results. Taking the nitrate ion substitution model as an example:

[0070] The total energy of the replaced surface composite system is approximately -408.9336 eV;

[0071] The total energy of the target crystal plane system before replacement was approximately -367.52118 eV;

[0072] The reference energy for a single nitrate ion is approximately -23.0617 eV;

[0073] The reference energy of a single fluoride ion is approximately -0.09065 eV.

[0074] Substituting into the above formula, the model energy difference of the replacement model can be obtained as follows:

[0075] ΔE ≈ 4.53 eV

[0076] Meanwhile, the vacuum reference energy level corresponding to the nitrate substitution model is approximately 3.43 eV, indicating a change in the surface potential distribution compared to the unsubstituted model. This result can serve as an auxiliary analytical basis for changes in the surface electrical environment after the introduction of impurities.

[0077] By outputting and displaying this energy difference, the impact of impurities on sodium fluorosilicate production can be obtained. This energy difference indicates the energy consumed in breaking the original bond and the energy released to form a new bond. If the energy difference is positive, it means that the process of nitrate replacing fluoride ions is energy-absorbing and thermodynamically non-spontaneous; for nitrate to replace fluoride ions on the crystal surface, an external energy supply of 4.53468 eV is required, reflecting that the ability of nitrate to replace fluoride ions is weak. Therefore, in the production process, there is no need to invest excessive costs in removing nitrate; simply controlling the nitrate content in the raw materials within a reasonable range can avoid its significant impact on crystal growth, providing a quantitative basis for cost optimization of the raw material impurity removal process. If the energy difference is negative, it means that the impurity ions have a strong ability to replace fluoride ions, and these impurity ions need to be removed as a key focus. Further, energy grading can be performed, and different prompts can be given based on the energy grading. In this way, the technical effect can be quantified by the change in energy difference, guiding the direction of production process optimization and avoiding blind trial and error in the research and development process.

[0078] It should be further noted that the above method can be written as a computer program and stored in a storage medium. The storage medium stores the computer program, and when the computer program is executed by a processor, it implements the steps of the above method. In this embodiment, the storage medium can be a storage medium installed in an electronic device, allowing the electronic device to read the contents of the storage medium and achieve the effects of the present invention. Alternatively, the storage medium can be a separate storage medium connected to an electronic device, enabling the electronic device to read the contents of the storage medium and implement the method steps of the present invention.

[0079] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection of the present invention.

Claims

1. A method for optimizing the production of sodium fluorosilicate, characterized in that, Includes the following steps: The crystal plane energy of sodium fluorosilicate at different crystal planes is calculated using the following formula: For crystal plane energy, It is the total energy of the relaxed slab model, that is, the energy of the system after the sodium fluorosilicate material is cut out of the surface; It is the energy of the bulk phase, that is, the energy of the complete bulk before cutting the slab model; n is the surface area of ​​the crystal plane; n is the number of bulk units. Select the crystal plane with the minimum crystal energy; For the crystal plane with the minimum crystal energy, the surface electrostatic potential is plotted and displayed using a preset electron density isosurface, and the energy is calculated. Obtain a preset number of impurity ions, calculate the energy required for the impurity ions to replace a preset number of fluorine ions in the crystal plane with the minimum crystal energy, calculate the energy difference after replacement based on the calculated energy, and output the result. The formula for calculating the energy difference is as follows: in, The energy difference between the models; The total energy of the crystal plane composite system after the replacement of the pre-defined impurity ions; To replace the total energy of the fluoride ion crystal plane system; The reference energy for a single preset impurity ion; The reference energy for a single replaced fluoride ion; m is the preset number of impurity ions, and it is the same as the number of fluorine ions being replaced.

2. The method for optimizing sodium fluorosilicate production according to claim 1, characterized in that: The impurity ions include nitrate ions.

3. The method for optimizing sodium fluorosilicate production according to claim 1, characterized in that: The preset quantity is 2.

4. The method for optimizing sodium fluorosilicate production according to claim 1, characterized in that: The preset quantity is 0.001au.

5. The method for optimizing sodium fluorosilicate production according to claim 1, characterized in that: The energy calculation process involves calling the VASP software package. The interaction between atoms and electrons is described using the projection-enhanced wave method. The electron wave function is expanded using a plane wave basis set, and the cutoff energy of the plane wave is adjusted according to a preset precision.

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