Stable electrochemical extraction design method of irregular titanium-containing electrode

Abstract

The invention discloses a stable electrochemical extraction design method of an irregular titanium-containing electrode, and belongs to the technical field of electrochemical metallurgy. The method is realized based on an in-situ detection device of high-temperature electrochemistry. The in-situ detection device comprises an X-ray source, an X-ray fluorescent screen, an aluminum-based alloy protective shell, a heating device, a rotary base, a quartz crucible, a crucible sealing cover with a hole and a vacuum pump. The implementation method comprises the following steps: adopting a 4D visualization method to realize real-time in-situ observation of spatial dissolution and deposition morphology change of the irregular titanium-containing electrode at any time, carrying out three-dimensional reconstruction on a CT image to realize numerical modeling of a real structure of the electrode, and establishing correlation between electrode morphology evolution and electrochemical parameters according to a numerical modeling result, so as to realize real-time in-situ observation of the titanium-containing electrode. According to the association, on the basis of non-uniform distribution of the overpotential in different spatial positions of the irregular titanium-containing electrode, a coaxial cathode matched with the irregular anode is designed, so that the non-uniform distribution of the overpotential is reduced, and stable electrochemical extraction is realized.

Description

Technical Field

[0001] The invention relates to a stable electrochemical extraction design method for an irregular titanium-containing electrode, belonging to the technical field of electrochemical metallurgy. Background Art

[0002] Metallic titanium has the advantages of low density, high specific strength, and corrosion resistance. Among them, high-purity metallic titanium and titanium alloys have memory functions, superconductivity, and hydrogen storage functions, and are widely used in military, aerospace and other fields. They are strategic resources with extraordinary value. In the existing utilization process of my country's characteristic vanadium-titanium magnetite, the titanium element is mainly found in high-titanium slag from electric furnaces and titanium-containing blast furnace slag. However, the process of extracting titanium from high-titanium slag has low utilization rate, heavy pollution, and a long process: Due to the high content of impurities such as CaO and MgO, Panxi titanium slag cannot be directly used in the boiling chlorination process to produce sponge titanium, and can only be used as a raw material for the production of titanium dioxide by the sulfuric acid method. Based on this, a green and efficient vanadium-titanium magnetite resource utilization process has become an inevitable choice.

[0003] In recent years, researchers have focused their attention on the preparation of metallic titanium and its alloys using titanium oxide as raw material through the molten salt electrolysis process, which avoids the chlorination process and has the characteristics of a short process flow. Representative processes include the Cambridge method (FFC method), the molten salt electrochemical calcium thermal reduction method (OS method), the soluble anode electrolytic titanium extraction method (USTB method) and the solid oxygen permeable membrane method (SOM method). Currently, the production of high-quality titanium products mainly relies on molten salt electrolysis. However, due to the harsh production environment of the high-temperature molten salt system, it is still necessary to rely on a large number of experimental results and production experience to optimize the process. Therefore, the development of a process design method based on a theoretical basis is of strategic significance for optimizing the production process of high-quality titanium products. Summary of the invention

[0004] In order to solve the problem that the existing methods cannot establish the electrode evolution theory through the in-situ characterization method, the purpose of the present invention is to provide a stable electrochemical extraction design method for irregular titanium-containing electrodes, so as to realize in-situ characterization based on 4D electrochemical visualization, realize real-time in-situ monitoring of electrode morphology evolution during electrolysis, establish the association between electrode morphology evolution and electrochemical parameters, and perform stable electrochemical extraction based on the association. The device used in the present invention is simple to operate, and the electrolysis environment is consistent with the commercial titanium molten salt electrolysis environment, which can ensure that the test results are complete and accurate.

[0005] To achieve the above object, the present invention adopts the following method:

[0006] The present invention discloses a stable electrochemical extraction design method for irregular titanium-containing electrodes. Based on an in-situ detection device of high-temperature electrochemistry and a 4D visualization method, the real-time in-situ observation of the dissolution and deposition morphology changes of irregular titanium-containing electrodes over time and space is realized. Based on the change law of irregular titanium-containing electrodes over time and space, a coaxial quasi-symmetrical cathode adapted to the structure of irregular titanium-containing electrodes is designed, and the local structure of the electrode is optimized based on the influence of spatial distribution on the dissolution rate. The in-situ detection device includes an X-ray source, an X-ray fluorescent screen, an aluminum-based alloy protective shell, a heating device, a rotating base, a quartz crucible, a crucible sealing cover containing holes, and a vacuum pump. After the X-rays penetrate the quartz crucible, data is collected through the X-ray fluorescent screen, and the three-dimensional morphology of the electrode is reconstructed based on the density difference; the protective shell adopts a double-layer structure, and the temperature is kept stable through water circulation; the quartz crucible is fixed on the rotating base, and the electrode is connected to the electrochemical workstation through the sealing cover to realize the in-situ observation of the electrolysis process. By reconstructing the CT images observed in situ in three dimensions, the numerical modeling of the real structure of the electrode is realized, and the association between the electrode morphology evolution and the electrochemical parameters is established based on the numerical modeling results, and stable electrochemical extraction is performed based on the association. The electrochemical parameters include spatial current density and overpotential distribution.

[0007] As an improvement of the stable electrochemical extraction design method of an irregular titanium-containing electrode described in the present invention, the electrochemical parameters extracted by the method are input into an electrochemical workstation to analyze working conditions such as different current densities, cell voltages, and multiple current steps.

[0008] As an improvement of the stable electrochemical extraction design method of an irregular titanium-containing electrode described in the present invention, the design method can be applied to any electrochemical system under the test conditions of a 4D in-situ visualization device, including but not limited to aqueous solution systems, room temperature ionic liquid systems, high temperature molten salt electrochemical systems (<1100°C), etc.

[0009] As an improvement of the design method for stable electrochemical extraction of irregular titanium-containing electrodes described in the present invention, the quantitative analysis process in the method includes but is not limited to establishing a quantitative relationship between electrochemical parameters such as current density and overpotential and condition parameters, and establishing a quantitative evaluation method for current density and overpotential. The condition parameters include applied current and electrode spatial position.

[0010] As an improvement of the stable electrochemical extraction design method of an irregular titanium-containing electrode described in the present invention, the irregular titanium-containing electrode includes but is not limited to impure titanium metal electrodes (sponge titanium, titanium alloy, etc.), titanium oxide electrodes, titanium carbon oxide electrodes, etc.

[0011] As an improvement on the stable electrochemical extraction design method of an irregular titanium-containing electrode described in the present invention, the design method is based on a quantitative analysis of the dissolution rate obtained by in-situ observation of the electrode, and a quantitative relationship between current density and overpotential and electrode depth and electrolysis time is established. By establishing a relationship between the electrode dissolution / deposition process and the electrolysis parameters and a numerical simulation model, an electrode design evaluation method is constructed.

[0012] As an improvement of the design method for stable electrochemical extraction of irregular titanium-containing electrodes described in the present invention, the electrode design is performed based on the results of quantitative analysis of in-situ characterization data, including designing the shape of the adapter electrode and optimizing the structure of the adapter electrode. The shapes include coaxial double arcs, pictograms, and double semi-squares. The structural optimization includes chamfering.

[0013] Beneficial Effects

[0014] 1. The present invention provides a stable electrochemical extraction design method for irregular titanium-containing electrodes, so as to realize in-situ characterization based on 4D electrochemical visualization, realize real-time in-situ monitoring of electrode morphology evolution during electrolysis, realize in-situ data collection and quantitative analysis of irregular titanium-containing electrodes in electrochemical processes based on in-situ monitoring data, establish a correlation between titanium-containing electrode morphology and multiple electrochemical parameters, and facilitate the design of an adaptive anode for irregular titanium-containing electrodes. The present invention has the advantages of high safety and simple implementation.

[0015] 2. The present invention provides a method for designing stable electrochemical extraction of an irregular titanium-containing electrode. Based on the uneven distribution of overpotential at different spatial positions of the irregular titanium-containing electrode, a coaxial cathode adapted to the irregular anode is designed to reduce the uneven distribution of overpotential and achieve the effect of stable electrochemical extraction.

[0016] 3. The present invention provides a design method for stable electrochemical extraction of irregular titanium-containing electrodes. Based on the uneven distribution of overpotential along the depth direction of the electrode, the overpotential at the edge of the electrode is reduced by chamfering the adapter electrode, thereby achieving stable electrochemical extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic diagram of an in-situ detection device used in a stable electrochemical extraction design method for an irregular titanium-containing electrode.

[0018] Figure 2 Schematic diagram of quartz crucible and fixed base.

[0019] Figure 3 Schematic diagram of an irregular titanium sponge electrode.

[0020] Figure 4 Schematic diagram of a custom cathode design.

[0021] Figure 5 is the current density-overpotential range for stable electrolysis in actual cases.

[0022] Among them: 1-aluminum-based alloy protective shell, 2-halogen lamp heating device, 3-rotating base, 4-crucible sealing cover (including holes), 5-quartz crucible, 6-capillary quartz tube, 7-electrode wire, 8-irregular sponge titanium electrode, 9-crucible base, 10-coaxial cathode, 11-pictographic cathode, 12-double semi-square cathode, 13-double arc cathode. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the laminated and wound battery cell embodiments and the accompanying drawings of the specification, but the embodiments of the present invention are not limited thereto.

[0024] The schematic diagram of the in-situ detection device structure of a stable electrochemical extraction design method for an irregular titanium-containing electrode used in this embodiment is as follows: Figure 1 As shown, the in-situ detection device includes an X-ray source, an X-ray fluorescent screen, an aluminum-based alloy protective housing 1, a halogen lamp heating device 2, a rotating base 3, a crucible sealing cover (including holes) 4, a quartz crucible 5, a capillary quartz tube 6, an electrode wire 7, a crucible base 9, and a vacuum pump, wherein the heating device is a halogen lamp with four identical focal points, the electrode is connected to the electrochemical workstation through an electric shock rod, the electrode rod is connected and sealed to the top of the capillary quartz tube through AB glue, and a sealing ring is installed between the capillary quartz tube and the crucible sealing cover to ensure that the environment inside the crucible is airtight. The bottom of the quartz crucible is connected to the rotating base through a thermosetting glue.

[0025] The anode material system is a square titanium sponge 8 with a rough surface, such as Figure 3 As shown, the negative electrode is a nickel wire with a diameter of 1 mm. The evolution of the uneven dissolution morphology of the anode during electrolysis is analyzed, and the design scheme of the cathode under stable electrolysis conditions is established based on the data results. A 0.035A constant current electrolysis experiment was carried out. A rotating CT scan was performed every 1 hour to obtain the in-situ image of the electrode, and this was repeated 4 times. The CT image was imported into AVIZO for three-dimensional reconstruction, and numerical modeling was performed through Abuqus to establish a quantitative relationship between the dissolved volume, surface area, current density, and overpotential variables. According to the quantitative relationship, the following is achieved: Figure 4 The electrode designs shown in 10-13.

[0026] This embodiment discloses a stable electrochemical extraction design method and a test method for an irregular titanium-containing electrode, and the specific implementation steps are as follows:

[0027] Step 1: Obtaining in-situ experimental parameters:

[0028] The morphological image of the electrode during in-situ electrolysis is obtained based on the in-situ detection device, and the parameters such as the surface area S, volume V, and dissolution rate r of the electrode are obtained by the three-dimensional reconstruction method.

[0029] Step 2: Establish a theoretical model for irregular electrode dissolution.

[0030] Step 2.1: Calculation of current density i and overpotential η: The electrode is segmented in the vertical direction. The relationship between the dissolution volume ΔV, surface area S, current density i, and overpotential η in the electrolysis process of irregular electrodes is as follows:

[0031] i=ΔV k ρn / MFS k t,

[0032] Where ΔV k is the volume of the kth electrode dissolved during the electrolysis process, and ΔV=∑ΔV k , ρ is the density of active substances, n is the number of charge transferred by the reaction, M is the molar mass of the active substances, F is the Faraday constant, S k is the electrode surface area, and S = ∑S k , t is the electrolysis time.

[0033] The overpotential η can be calculated from the current density using the BV equation:

[0034] i=i0(e -(1+α)fη -e (1-α)fη ),

[0035] Where i0 is the exchange current density of the object electrode, which can be measured by the Tafel method; α represents the electrode reaction transfer coefficient, and in this process, α=0.5; is a constant, n is the number of charges transferred in the reaction, F is the Faraday constant, R is the gas constant, T is the temperature; η is the overpotential.

[0036] Step 2.2: Fitting of current density and overpotential: Establish the connection between electrode electrochemical parameters and electrode morphology, that is, set the current density i(x, t) as a composite function of the electrode spatial position and electrolysis time, where x is the distance between the electrode and the molten salt surface, and t is the electrolysis time.

[0037] Based on the current density of different electrode segments at different times calculated in step 2.1, the following expression is obtained:

[0038]

[0039] Where A, B, and C are constants. In this case, A = 0.05, B = 0.8, and C = 0.03. m1 is an intrinsic parameter related to the electrode material, and m2 is proportional to the total current of cross-current electrolysis. It should be noted that the value range of x is (0, 1), dimensionless, with x = 0 representing the top of the electrode and x = 1 representing the bottom of the electrode.

[0040] Similarly, we can get the relationship between i and η in step 2.1:

[0041] i(x,t)=i0(e -(1+α)fη(x,t) -e (1-α)fη(x,t) )

[0042] The above formula can be used to calculate the anode surface overpotential when the electrode depth and electrolysis time are determined.

[0043] Step 2.3: Establishment of evaluation system: This method takes the uniformity and purity of the product during the electrode electrolysis process as the main evaluation indicators. By bringing the impurity deposition overpotential into the fitting formula established in step 2.2, the space and time intervals that meet the requirements of impurity non-precipitation are calculated to form an evaluation system. The specific establishment process is as follows:

[0044] The current density can be evaluated according to the following inequality:

[0045]

[0046] where i min is the minimum current density for impurity precipitation, which can be calculated by the BV equation. In this case, the current density at the bottom of the electrode is much higher than that at the rest, so x=1 is taken for calculation, and the precipitation of three impurities (Al, Mn, V) is used as the benchmark for evaluation, such as Figure 5 As shown: the area enclosed below the function is the stable electrolysis area, and the rest is the impurity precipitation area.

[0047] Step 3: Establish a numerical simulation model.

[0048] The above theoretical model is applied to the numerical simulation system to realize the electrode design ( Figure 4 In this actual case, the Nernst-Planck model of tertiary current distribution is used to simulate the evolution of overpotential and current density during electrolysis. The current density distribution on the electrode surface is obtained through simulation, and the electrode surface is divided into two parts according to the above evaluation system: min , the area of ​​impurity precipitation is S1; below the threshold i min , the area S2 that can stabilize electrolysis. By calculating the proportion P of the electrode surface area that meets the stable electrolysis conditions, that is:

[0049]

[0050] The larger the P value, the more stable the electrode process. By combining simulations, the current density and overpotential distribution on the electrode surface can be obtained, providing a reference for the next step of electrode design. For example, in this reagent case, it can be found that the current density on the anode surface close to the cathode is higher, so a surround cathode structure design is used in the follow-up. Similarly, the anode structure design is carried out in the same way, and the cathode is placed in the center, which can improve the uniformity and stability of cathode deposition. At the same time, the P value can be used to evaluate the improvement effect of electrode design on stable electrolysis.

[0051] Step 4: Electrode structure design.

[0052] Based on the simulation results of the previous step, the electrode design is carried out. In this reagent case, it can be found that the current density of the anode surface close to the cathode is higher, so the surrounding cathode structure design is adopted in the subsequent step, such as Figure 4 Electrode design schemes 10-13. First, by simulating the designed electrodes, the statistical results show that the P value is increased by about 50% compared with the unoptimized system (double rod electrodes), indicating that the design scheme significantly optimizes the stability of the electrolysis process.

[0053] Step 5: Experimental verification of design results.

[0054] This work process adopts the expanded experiment to test the results. Figure 4 The Ti content of the electrolytic products obtained by electrode design schemes 10-13 is above 98%, which is higher than the 93% obtained by the original system, indicating that the overall analysis and design process is feasible.

[0055] The method of the present invention can be used for quantitative and qualitative analysis of electrolysis parameters, overpotential, current density, etc. in the electrolysis process of multi-system and multi-type titanium-containing electrodes. Through in-situ observation of the electrolysis process; CT images are three-dimensionally reconstructed through professional software to achieve numerical modeling of the real structure of the electrode, quantitative analysis and theoretical establishment, and then design optimization for factors that may destroy stable electrolysis.

[0056] According to the above description, the embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. The present invention is described in detail with reference to the above embodiments. Those skilled in the art can still modify or replace the specific implementations of the present invention with equivalents. Any modifications or equivalents that do not deviate from the spirit and scope of the present invention are within the scope of protection of the pending claims. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for designing stable electrochemical extraction of irregular titanium-containing electrodes, characterized in that: An in-situ detection device based on high temperature electrochemistry and a 4D visualization method are used to realize real-time in-situ observation of the dissolution and deposition morphology changes of irregular titanium-containing electrodes over time and space. Based on the change law of irregular titanium-containing electrodes over time and space, a coaxial symmetrical cathode adapted to the structure of irregular titanium-containing electrodes is designed, and the local structure of the electrode is optimized based on the influence of spatial distribution on the dissolution rate. The in-situ detection device includes an X-ray source, an X-ray fluorescent screen, an aluminum-based alloy protective shell, a heating device, a rotating base, a quartz crucible, a crucible sealing cover with holes, and a vacuum pump. X-rays penetrate quartz Data is collected through an X-ray fluorescent screen behind the crucible, and the three-dimensional morphology of the electrode is reconstructed based on the density difference; the protective shell adopts a double-layer structure, and the temperature is kept stable by water circulation; the quartz crucible is fixed on a rotating base, and the electrode is connected to the electrochemical workstation through a sealing cover to achieve in-situ observation of the electrolysis process; by three-dimensionally reconstructing the in-situ observed CT image, the numerical modeling of the real structure of the electrode is achieved, and the correlation between the electrode morphology evolution and the electrochemical parameters is established based on the numerical modeling results, and stable electrochemical extraction is performed based on the correlation; the electrochemical parameters include spatial current density and overpotential distribution.

2. A method for designing stable electrochemical extraction of irregular titanium-containing electrodes as claimed in claim 1, characterized in that: Irregular titanium-containing electrodes include but are not limited to impure titanium metal electrodes, titanium oxide electrodes, and titanium carbon oxide electrodes; impure titanium metal electrodes include sponge titanium and titanium alloys.

3. The method for designing stable electrochemical extraction of an irregular titanium-containing electrode as claimed in claim 1, characterized in that: The surface area, volume and dissolution rate of the electrode were obtained through three-dimensional reconstruction method.

4. The method for designing stable electrochemical extraction of an irregular titanium-containing electrode as claimed in claim 1, characterized in that: By segmenting the electrode along the height direction, the local current density and overpotential of each section of the electrode are calculated, and the quantitative relationship between the current density and overpotential, electrode depth and electrolysis time is established.

5. The method for designing stable electrochemical extraction of an irregular titanium-containing electrode as claimed in claim 1, characterized in that: The threshold overpotential and current density of impurity dissolution are compared with the local overpotential and current density of the electrode to evaluate whether the anodic process is stable.

6. The method for designing stable electrochemical extraction of irregular titanium-containing electrodes according to claim 1, characterized in that: The numerical simulation method is combined with the quantitative analysis results to calculate the surface area percentage where the surface overpotential does not exceed the dissolution of impurities. The stability of the electrolysis process is evaluated by analyzing the proportion of the surface area without impurity dissolution.

7. The method for designing stable electrochemical extraction of an irregular titanium-containing electrode as claimed in claim 1, characterized in that: Electrode design is performed based on the results of quantitative analysis of in-situ characterization data, including designing the shape of the adaptor electrode and optimizing the structure of the adaptor electrode; the shapes include coaxial double arcs, pictograms, and double semi-squares; The structural optimization includes chamfering.

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