Method for measuring sodium expansion of non-standard size aluminum cathode under pressure

Abstract

The application belongs to the technical field of material detection, and specifically provides a method for determining the sodium expansion rate of an aluminum cathode with a non-standard size under pressure, characterized in that the method comprises the following steps: preparing a composite sample through an aluminum cathode carbon block and a graphite block, and preparing a control sample through the graphite block; electrolyzing the composite sample and the control sample respectively; determining a first length increment curve of the composite sample in an electrolysis process, and determining a second length increment curve of the control sample in the electrolysis process; and determining the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve. The technical scheme provided in the application can realize the determination of the sodium expansion rate of an aluminum cathode with a non-standard size.

Description

Technical Field

[0001] This application belongs to the field of materials testing technology, and in particular relates to a method for determining the sodium expansion rate of a non-standard sized aluminum cathode under pressure. Background Technology

[0002] With the continuous upgrading of technology and the in-depth research and development of new materials in the aluminum electrolysis industry, aluminum cathode carbon blocks, as the core and key material of electrolytic cells, have their sodium expansion rate directly reflecting their resistance to sodium corrosion. This directly affects the service life of electrolytic cells and the stable and efficient operation of aluminum electrolysis production, and is of great significance to improving the quality and efficiency of the industry. However, the current sodium expansion rate testing method is only applicable to standard cylinders with a diameter of 30.0 mm ± 0.1 mm and a length of 60.0 mm ± 1 mm. Small fragments and small-sized test samples generated in actual production and research and development cannot be processed into standard sizes, making the existing testing methods unsuitable. Therefore, how to determine the sodium expansion rate of aluminum cathodes with non-standard dimensions under pressure has become an urgent technical problem to be solved. Summary of the Invention

[0003] The embodiments of this application provide a method for determining the sodium expansion rate of a non-standard sized aluminum cathode under pressure, thereby enabling the determination of the sodium expansion rate of a non-standard sized aluminum cathode under pressure.

[0004] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0005] According to a first aspect of the present application, a method for determining the sodium expansion rate of a non-standard sized aluminum cathode under pressure is provided, characterized in that the method includes: preparing a composite sample using a cathode carbon block and a graphite block, and preparing a control sample using a graphite block; electrolyzing the composite sample and the control sample respectively; determining a first length increment curve of the composite sample during electrolysis, and determining a second length increment curve of the control sample during electrolysis; and determining the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve.

[0006] In some embodiments of this application, based on the foregoing scheme, the preparation of a composite sample using a cathode carbon block and a graphite block, and the preparation of a control sample using a graphite block, includes: processing the cathode carbon block into a carbon block column with a preset diameter and a first preset length, and processing the graphite block into a first graphite column with a preset diameter and a second preset length; connecting and fixing the carbon block column and the first graphite column to obtain a composite sample with a third preset length; and processing the graphite block into a second graphite column with a preset diameter and a third preset length to obtain a control sample, wherein the third preset length is equal to the sum of the first preset length and the second preset length.

[0007] In some embodiments of this application, based on the aforementioned scheme, the first preset length is 20mm to 50mm, the second preset length is 50mm to 80mm, and the third preset length is 100mm.

[0008] In some embodiments of this application, based on the aforementioned scheme, the composite sample is electrolyzed, including: placing a corundum disc at the bottom of a graphite crucible and placing the composite sample on the corundum disc, such that the composite sample is located in the center of the corundum disc; uniformly adding a predetermined mass of electrolyte into the inside of the graphite crucible, and assembling the crucible lid and insulating ring at the top of the graphite crucible; heating the assembled graphite crucible to a predetermined temperature under a predetermined pressure; using the assembled graphite crucible as the anode and the composite sample as the cathode, electrolysis is performed at a predetermined current density for a predetermined duration.

[0009] In some embodiments of this application, based on the aforementioned scheme, electrolysis of the control sample includes: placing a corundum disc at the bottom of a graphite crucible and placing the control sample on the corundum disc, such that the control sample is located in the center of the corundum disc; uniformly adding a predetermined mass of electrolyte into the inside of the graphite crucible, and assembling the crucible lid and insulating ring at the top of the graphite crucible; heating the assembled graphite crucible to a predetermined temperature under a predetermined pressure; and performing electrolysis at a predetermined current density for a predetermined duration, using the assembled graphite crucible as the anode and the control sample as the cathode.

[0010] In some embodiments of this application, based on the foregoing scheme, the electrolyte comprises 71.5% by mass of Na3AlF6, 14.5% by mass of NaF, 5.0% by mass of CaF2, and 9.0% by mass of Al2O3.

[0011] In some embodiments of this application, based on the foregoing scheme, the preset temperature is 975°C to 985°C, and the preset current density is 0.6 A / cm². 2 Up to 0.8A / cm 2 The preset duration is 1.5h to 2.5h.

[0012] In some embodiments of this application, based on the foregoing scheme, determining the first length increment curve of the composite sample during electrolysis includes: obtaining the length increment of the composite sample at various moments during the electrolysis process to obtain the first length increment curve of the composite sample.

[0013] In some embodiments of this application, based on the foregoing scheme, determining the second length increment curve of the control sample during electrolysis includes: obtaining the length increment of the control sample at various times during the electrolysis process to obtain the second length increment curve of the control sample.

[0014] In some embodiments of this application, based on the foregoing scheme, determining the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve includes: The expansion rate curve of the aluminum cathode is determined by the following formula:

[0015] in, The expansion rate curve of the aluminum cathode is shown. This represents the first length increment curve of the composite sample; This represents the second length increment curve of the control sample; Indicates the first preset length; The second preset length is indicated; the maximum value in the expansion rate curve of the aluminum cathode is taken as the sodium expansion rate of the aluminum cathode.

[0016] Based on the technical solution proposed in this application, a composite sample composed of non-standard size cathode carbon block and graphite block and a control sample made only of graphite block are prepared respectively. Electrolytic tests are performed on the two sets of samples under completely uniform simulated electrolysis conditions. The length increment of the two sets of samples during the entire electrolysis process can be obtained simultaneously, and the sodium expansion data of non-standard size aluminum cathode can be accurately obtained. This solves the technical problem that the existing detection methods are only applicable to standard size samples and cannot detect non-standard size cathode samples.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A flowchart of a method for determining the sodium expansion rate of a non-standard sized aluminum cathode according to one embodiment of this application is shown. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0021] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0022] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0023] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.

[0024] With the continuous upgrading of technology and the in-depth research and development of new materials in the aluminum electrolysis industry, aluminum cathode carbon blocks, as the core key material of electrolytic cells, directly reflect the sodium expansion rate of the cathode, which is related to the service life of electrolytic cells and the stable and efficient operation of aluminum electrolysis production. This is of great significance to improving the quality and efficiency of the industry. However, the current sodium expansion rate detection method is only applicable to standard cylinders with a diameter of 30.0 mm ± 0.1 mm and a length of 60.0 mm ± 1 mm. Small fragments and small-sized test samples generated in actual production and research and development cannot be processed into standard sizes, making the existing measurement methods unsuitable. Therefore, this application proposes a method for determining the sodium expansion rate of non-standard sized aluminum cathodes under pressure, so as to realize the determination of the sodium expansion rate of non-standard sized aluminum cathodes under pressure.

[0025] Next, we will combine Figure 1 This paper elaborates in detail the method for determining the sodium expansion rate of non-standard sized aluminum cathodes proposed in this application.

[0026] Please refer to Figure 1 The diagram illustrates a flowchart of a method for determining the sodium expansion rate of a non-standard sized aluminum cathode according to one embodiment of this application. The method may specifically include the following steps 110 to 140: Step 110: Prepare a composite sample using a cathode carbon block and a graphite block, and prepare a control sample using a graphite block.

[0027] Step 120: Electrolyze the composite sample and the control sample respectively.

[0028] Step 130: Determine the first length increment curve of the composite sample during electrolysis, and determine the second length increment curve of the control sample during electrolysis.

[0029] Step 140: Determine the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve.

[0030] In this application, the non-standard size aluminum cathode refers to a cathode material whose sodium expansion rate cannot be tested using existing standard methods because it cannot be processed into a standard cylindrical sample. The sodium expansion rate refers to the expansion caused by sodium elements in the electrolyte penetrating into the carbon block under pressure in an electrolytic working environment. This expansion ratio is a core indicator for evaluating the sodium corrosion resistance of the cathode carbon block and directly determines the service life of the electrolytic cell. The composite sample is the assembly to be tested, which is made by splicing the non-standard size cathode carbon block to be tested with a graphite block. The control sample is a blank control, which is made only from a graphite block and is used to subtract the expansion of the graphite material under the electrolytic environment. The length increment is the change in length of the sample at different time points during the entire electrolysis process, as recorded in real time by the detection equipment, relative to the length before the start of electrolysis. The data formed by corresponding time and length increment fully presents the dynamic change process of the sample's expansion.

[0031] In this application, the composite sample needs to be made by combining the cathode carbon block to be tested with a graphite block, while the control sample is made by processing a graphite block alone. During the preparation process, it is necessary to ensure that the shape and key dimensions of the two types of samples are consistent, and that the graphite blocks used are from the same batch and of the same material, so as to eliminate the detection deviation caused by material differences.

[0032] In this application, two types of samples are subjected to independent electrolytic tests. The electrolytic process simulates the real working environment of an aluminum electrolytic cell, including applying a fixed working pressure, heating to the electrolytic operating temperature, using a uniform electrolyte ratio, and using the same electrolytic parameters to ensure that the test environment of the composite sample and the control sample is completely consistent, thus avoiding interference from external conditions with the test results.

[0033] In this application, during the entire electrolysis period, the detection device continuously collects the length change data of the composite sample and generates a first length increment curve, while simultaneously collecting the length change data of the control sample and generating a second length increment curve. The two curves provide complete basic data for subsequent accurate calculations.

[0034] In this application, the final sodium expansion rate is calculated by combining two length increment curves. The real-time expansion rate is calculated by combining the values ​​of the first and second length increment curves with the original length of the non-standard cathode carbon block. Finally, the maximum value during the expansion process is determined as the sodium expansion rate of the non-standard size aluminum cathode. The calculation method complies with the industry testing judgment rules and ensures the validity of the results.

[0035] In this application, a composite sample composed of a cathode carbon block and a graphite block and a control sample composed only of a graphite block are prepared respectively. Electrolytic tests are performed on the two sets of samples under completely uniform simulated electrolysis conditions. The length increment curves of the two sets of samples during the entire electrolysis process can be obtained simultaneously, and the sodium expansion data of the non-standard size aluminum cathode itself can be accurately obtained. This solves the technical problem that the existing detection methods are only applicable to standard size samples and cannot detect non-standard size cathode samples.

[0036] In step 110 above, the preparation of the composite sample using the cathode carbon block and the graphite block, and the preparation of the control sample using the graphite block, can be specifically performed according to steps 111 to 113 as follows: Step 111: Process the cathode carbon block into a carbon block column with a preset diameter and a first preset length, and process the graphite block into a first graphite column with a preset diameter and a second preset length.

[0037] Step 112: Connect and fix the carbon block column and the first graphite column to obtain a composite sample of a third preset length.

[0038] Step 113: The graphite block is processed into a second graphite column with a preset diameter and a third preset length to obtain a control sample, wherein the third preset length is equal to the sum of the first preset length and the second preset length.

[0039] In this application, the first preset length is 20mm to 50mm, the second preset length is 50mm to 80mm, and the third preset length is 100mm. The sum of the first preset length and the second preset length is equal to the third preset length. For example, the first preset length can be 20mm and the second preset length can be 80mm; the first preset length can also be 30mm and the second preset length can be 70mm; the first preset length can also be 40mm and the second preset length can be 60mm. This application does not specifically limit the specific values ​​of these values. In this application, the preset diameter is a fixed diameter value determined by combining the adaptation requirements of the sodium expansion rate detection equipment and industry testing standards, specifically 30mm±0.1mm; the first preset length is the length of the carbon block column processed from the cathode carbon block to be tested, which can cover the available processing length of various cathodes such as production residues and small R&D samples; the carbon block column is a cylindrical component processed from the cathode carbon block to be tested for aluminum, and is the core test object for sodium expansion rate detection, and its material is completely consistent with the cathode carbon block used in actual applications.

[0040] In this application, the first graphite column is a cylindrical component made of high-purity graphite, used to splice with the carbon block column so that the total length of the combined sample matches the testing conditions; the second preset length is the processing length of the first graphite column, which will be adjusted according to the first preset length of the carbon block column; the third preset length is the total length after the carbon block column and the first graphite column are spliced ​​together, and it is also the processing length of the second graphite column; the second graphite column is a cylindrical component made only of high-purity graphite, serving as a blank control sample.

[0041] In this application, the connection and fixation involves tightly connecting the carbon block column and the first graphite column coaxially along the axial direction to ensure that no relative displacement occurs during the test and to ensure accurate detection of length changes; the composite sample is the combined sample to be tested, which is spliced ​​together from the carbon block column and the first graphite column, and is used to simulate the expansion state of the aluminum cathode under electrolysis conditions; the control sample is a blank reference sample, which consists only of the second graphite column and is used to collect the expansion data of graphite under the same test environment.

[0042] In this application, the cathode carbon block to be tested is processed into a carbon block column with a preset diameter, and a graphite block is processed into a first graphite column with the same preset diameter. The length of the carbon block column is the first preset length, and the length of the first graphite column is the second preset length. The two have the same diameter to avoid deviation in the test results due to different diameters. The processed carbon block column and the first graphite column are then coaxially connected and fixed to form a complete cathode. The total length of this composite sample is the third preset length.

[0043] In this application, graphite blocks from the same batch are individually processed into second graphite columns with the same preset diameter and third preset length. The third preset length is the sum of the first preset length and the second preset length, ensuring that the test combination sample and the blank control sample are completely consistent in terms of physical dimensions.

[0044] In this application, by processing the cathode carbon block to be tested into a carbon block column with a fixed preset diameter, processing the graphite block into a first graphite column with the same preset diameter and connecting and fixing it with the carbon block column to form a composite sample with a uniform total length, and processing the graphite block into a second graphite column with the same total length as a control sample, and by uniformizing the sample diameter and total length and using the same batch of graphite material to prepare matching parts, the detection interference caused by size difference and material difference is effectively eliminated, thereby improving the accuracy of the determination of the sodium expansion rate of non-standard size aluminum cathodes.

[0045] In step 120 above, the composite sample is electrolyzed, which can be specifically performed according to steps 121 to 124 as follows: Step 121: Place the corundum disc at the bottom of the graphite crucible and place the composite sample on the corundum disc, so that the composite sample is located in the center of the corundum disc.

[0046] Step 122: Add the preset mass of electrolyte evenly into the graphite crucible, and assemble the crucible lid and insulating ring on the top of the graphite crucible.

[0047] Step 123: Heat the assembled graphite crucible to a preset temperature under a preset pressure.

[0048] Step 124: Electrolysis is performed using the assembled graphite crucible as the anode and the composite sample as the cathode at a preset current density for a preset duration.

[0049] Furthermore, in step 120 above, the control sample is electrolyzed, which can be specifically performed according to steps 125 to 128 as follows: Step 125: Place the corundum disc at the bottom of the graphite crucible and place the reference sample on the corundum disc, so that the reference sample is located in the center of the corundum disc.

[0050] Step 126: Add the preset mass of electrolyte evenly into the graphite crucible, and assemble the crucible lid and insulating ring on the top of the graphite crucible.

[0051] Step 127: Heat the assembled graphite crucible to a preset temperature under a preset pressure.

[0052] Step 128: Electrolysis is performed using the assembled graphite crucible as the anode and the control sample as the cathode at a preset current density for a preset duration.

[0053] In this application, the preset mass can be 750g to 770g of electrolyte, specifically 765g, and the molecular ratio of the electrolyte is 4.0. It is a special test electrolyte prepared to simulate the actual working medium of an industrial aluminum electrolysis cell, with fixed composition and ratio, which can provide a stable sodium permeation environment for the cathode carbon block.

[0054] In this application, the graphite crucible is a high-temperature resistant container made of high-purity graphite, which serves the dual function of holding electrolyte and acting as an electrolytic anode during testing. Graphite material is electrically stable, resistant to high-temperature corrosion, and suitable for the high-temperature and high-pressure conditions of electrolytic testing. The preset pressure is the actual external load applied to the aluminum liquid, electrolyte, and cathode carbon block, which is one of the core conditions for the sodium expansion rate test under pressure. Specifically, it is 4MPa to 6MPa, and can be 5MPa. The preset temperature is the actual working temperature of industrial aluminum electrolysis, which can ensure that the electrolyte is fully melted. Specifically, it is 975℃ to 985℃, and can be 980℃.

[0055] In this application, the preset current density is the industry-standard cathode sodium expansion rate test current parameter, which ensures a stable sodium permeation rate during electrolysis and makes the test results comparable; specifically, it is 0.6 A / cm.2 Up to 0.8A / cm 2。 For example, it could be 0.7 A / cm²; the preset duration is the time required to ensure that sodium fully penetrates into the sample and allows the carbon block to expand to a stable state, specifically 1.5 h to 2.5 h, for example, 2 h.

[0056] In this application, the electrolyte comprises 71.5% by mass of Na3AlF6, 14.5% by mass of NaF, 5.0% by mass of CaF2, and 9.0% by mass of Al2O3. This application does not impose specific limitations on this.

[0057] In this application, firstly, a corundum disc is placed at the bottom of a graphite crucible, and the control sample is placed on the corundum disc, with the control sample located in the center of the corundum disc. Electrolyte of a predetermined mass is evenly added into the inside of the graphite crucible, and then the crucible lid and insulating ring at the top of the graphite crucible are assembled.

[0058] In this application, a preset pressure is then applied to the assembled graphite crucible system to simulate the stress state of the cathode carbon block in the electrolytic cell. At the same time, the system is continuously heated to a preset temperature so that the electrolyte is completely melted and reaches the working temperature required for the electrolytic reaction. After the system has expanded at high temperature, the graphite crucible is used as the anode and the pre-prepared composite sample is used as the cathode. Electrolysis is carried out according to a preset current density, and the electrolysis process is maintained for a preset duration.

[0059] In this application, during the entire electrolysis process, sodium in the electrolyte continuously penetrates into the cathode under the action of the electric field, causing the carbon block to expand and deform. The fixation and uniformity of various parameters can completely eliminate the interference of external environment and operating condition fluctuations on the test results, providing real and stable basic data for subsequent length change detection and sodium expansion rate calculation.

[0060] In this application, all operational procedures and parameter settings for the electrolysis steps of the control sample are completely consistent with the electrolysis conditions of the composite sample. A corundum disc is placed at the bottom of a graphite crucible, and the composite sample is placed on the corundum disc, with the composite sample positioned in the center of the disc. A predetermined mass of electrolyte is uniformly added to the inside of the graphite crucible, and the crucible lid and insulating ring are assembled on top. During this process, the same predetermined mass of electrolyte as used in the test of the composite sample is weighed to ensure that the amount and composition of the electrolyte are identical. A predetermined pressure is then applied to the assembled graphite crucible system; this pressure is exactly the same as the pressure used in the test of the sample, simulating a consistent stress environment. Simultaneously, the system is heated to a predetermined temperature, causing the electrolyte to reach the same melting state as in the test of the sample. After the system has expanded at high temperature, electrolysis is performed using the graphite crucible as the anode and the control sample as the cathode, according to a predetermined current density, and the electrolysis process is maintained for a predetermined duration. By collecting the length change data of the sample throughout the entire process, the expansion rate of graphite can be obtained, providing a reliable basis for subsequently eliminating the interference data of graphite material in the test composite sample.

[0061] In this application, a fixed mass of a special electrolyte is weighed and added to a graphite crucible. The assembled graphite crucible is heated to a preset temperature under a preset pressure. Then, the graphite crucible is used as the anode and the composite sample or control sample is used as the cathode. Electrolysis is performed for a preset time according to a preset current density, thereby accurately determining the sodium expansion rate of the non-standard cathode. This solves the technical problem that existing standard testing methods are only applicable to samples of fixed size and cannot detect non-standard samples. It can meet the practical needs of small-size cathode sample performance testing in aluminum electrolysis production and new material research and development.

[0062] In step 130 above, determining the first length increment curve of the composite cathode during electrolysis can be specifically performed according to step 131 below: Step 131: Obtain the length increment of the composite sample at various moments during the electrolysis process to obtain the first length increment curve of the composite sample.

[0063] In this application, the electrolysis process refers to the complete test process of electrolyzing a composite sample under set pressure, temperature, and current density conditions, covering the entire period from the start to the end of electrolysis. Each time point is a multiple time node selected at fixed intervals during the electrolysis process. The detection device continuously collects length increment data at these nodes, fully covering the entire electrolysis process. The length increment refers to the axial length increment of the composite sample at the corresponding time point, accurately collected by the displacement detection module of the sodium expansion rate measuring instrument. This value includes the expansion of the cathode carbon block and the first graphite column under test. In this application, during the entire electrolysis test, the detection device continuously collects real-time axial length increments at different time nodes. These real-time length increment data can reflect the expansion of the non-standard cathode carbon block and the first graphite column caused by sodium penetration. By mapping the time data of all time nodes during the electrolysis process to the corresponding length increment data one by one and continuously integrating them in chronological order, a complete first length increment curve can be obtained. This curve can intuitively present the expansion trend of the composite sample throughout the electrolysis process. It can retain the total expansion information of the carbon block and graphite extension rod under test, providing comprehensive and accurate raw data for subsequent elimination of expansion interference from graphite components and calculation of the true sodium expansion rate of the cathode carbon block under test.

[0064] In this application, by obtaining the real-time length increment at each moment during the electrolysis of the composite sample and generating the first length increment curve, the total expansion change state of the composite sample throughout the electrolysis process can be completely and accurately recorded. This provides detailed and reliable raw data for subsequently eliminating the expansion interference caused by graphite materials, thereby effectively improving the accuracy of the cathode sodium expansion rate determination for non-standard sized aluminum.

[0065] In step 130 above, determining the second length increment curve of the control sample during electrolysis can be specifically performed according to step 132 below: Step 132: Obtain the length increment of the control sample at various times during the electrolysis process to obtain the second length increment curve of the control sample.

[0066] In this application, during the electrolysis of the control sample, a sodium expansion rate measuring instrument continuously collects the real-time axial length increment of the control sample at various time points. By integrating the time data and corresponding length increment data of all time points throughout the electrolysis process in chronological order, a complete second length increment curve can be formed.

[0067] In this application, by obtaining the real-time length increment at each moment during the electrolysis process of the control sample, a benchmark is provided for the subsequent calculation of the expansion data of the aluminum cathode, thereby effectively eliminating the test interference caused by the graphite component and improving the accuracy of the sodium expansion rate measurement of the non-standard size aluminum cathode.

[0068] In step 140 above, determining the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve can be specifically performed according to steps 141 to 142 as follows: Step 141, determine the expansion rate curve of the aluminum cathode using the following formula (1): (1) in, The expansion rate curve of the aluminum cathode is shown. This represents the first length increment curve of the composite sample; This represents the second length increment curve of the control sample; Indicates the first preset length; Indicates the second preset length; Step 142: Take the maximum value in the expansion rate curve of the aluminum cathode as the sodium expansion rate of the aluminum cathode.

[0069] In this application, the real-time values ​​of the first length increment and the second length increment collected during the electrolysis process, as well as the first preset length of the carbon block to be tested and the second preset length of the matching graphite extension rod, are substituted into a specified calculation formula to obtain the real-time expansion rate during the electrolysis process. The maximum value of the expansion rate is extracted as the final sodium expansion rate.

[0070] The technical solution proposed in this application will be described in detail below with reference to some specific embodiments.

[0071] Example 1: Step 1: Preparation of carbon block columns and graphite columns.

[0072] Test group: The carbon block to be tested is processed into a carbon block column with a diameter of 30.0 mm and a length of 20 mm, and the matching graphite block is processed into the first graphite column with a diameter of 30.0 mm and a length of 80 mm.

[0073] Blank group: The graphite block is processed into a second graphite column with a diameter of 30.0 mm and a length of 100 mm.

[0074] Step 2: Weighing the electrolyte.

[0075] Weigh out 765g of electrolyte. The electrolyte molecular ratio is 4.0, and its mass percentage composition is: 71.5% Na3AlF6, 14.5% NaF, 5.0% CaF2, and 9.0% Al2O3.

[0076] Step 3: Determination of sodium expansion rate.

[0077] The sodium expansion rate of the blank group and the test group was measured using a sodium expansion rate measuring instrument. A pressure of 5 MPa was applied to the assembled graphite crucible system, and it was heated to 980℃±5℃. The graphite crucible was used as the anode, and the system consisting of the blank / test sample and the extension rod was used as the cathode. The pressure was 0.7 A / cm. 2 Electrolysis at a current density for 2 hours.

[0078] Based on the displacement changes measured in the blank group and the test group, the expansion rate of the test sample at time t is calculated, and the maximum expansion rate is the sodium expansion rate.

[0079] Example 2: The difference between this embodiment and Embodiment 1 lies in the preparation of the test sample and extension rod in step 1. In this embodiment, the test cathode carbon block is processed into a carbon block column with a diameter of 30.0 mm and a length of 30 mm, and the matching graphite block is processed into a first graphite column with a diameter of 30.0 mm and a length of 70 mm.

[0080] Example 3: The difference between this embodiment and Embodiment 1 lies in the preparation of the test sample and extension rod in step 1. In this embodiment, the test cathode carbon block is processed into a carbon block column with a diameter of 30.0 mm and a length of 40 mm, and the matching graphite block is processed into a first graphite column with a diameter of 30.0 mm and a length of 60 mm.

[0081] Example 4: The difference between this embodiment and Embodiment 1 lies in the preparation of the test sample and extension rod in step 1. In this embodiment, the test cathode carbon block is processed into a carbon block column with a diameter of 30.0 mm and a length of 50 mm, and the matching graphite block is processed into a first graphite column with a diameter of 30.0 mm and a length of 50 mm.

[0082] Comparative Example 1: Comparative Example 1 uses YS / T 63.5-2025 to test the cathode. The difference from Example 1 is that the carbon block of the cathode to be tested is processed into a carbon block column with a diameter of 30.0 mm and a length of 60 mm, and the matching graphite block is processed into a first graphite column with a diameter of 30.0 mm and a length of 40 mm.

[0083] The sodium expansion rate results for each embodiment and comparative example are shown in Table 1.

[0084]

[0085] Table 1 Sodium expansion rate of each embodiment As shown in Table 1, the test results based on the technical solution of this application have a small difference from the test results of the YS / T 63.5-2025 industry standard test method, indicating that the two methods have good comparability and can be used for the accurate determination of the sodium expansion rate of non-standard size aluminum cathodes.

[0086] Based on the technical solution proposed in this application, a composite sample composed of non-standard size cathode carbon block and graphite block and a control sample made only of graphite block are prepared respectively. Electrolytic tests are performed on the two sets of samples under completely uniform simulated electrolysis conditions. The length increment curves of the two sets of samples during the entire electrolysis process can be obtained simultaneously, and the sodium expansion data of the non-standard size aluminum cathode itself can be accurately obtained. This solves the technical problem that the existing detection methods are only applicable to standard size samples and cannot detect non-standard size cathode samples.

[0087] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for determining the sodium expansion rate of a non-standard sized aluminum cathode under pressure, characterized in that, The method includes: Composite samples were prepared using cathode carbon blocks and graphite blocks, while control samples were prepared using graphite blocks. The composite sample and the control sample were electrolyzed respectively; Determine the first length increment curve of the composite sample during electrolysis, and determine the second length increment curve of the control sample during electrolysis; The sodium expansion rate of the aluminum cathode is determined based on the first length increment curve and the second length increment curve.

2. The method according to claim 1, characterized in that, The preparation of the composite sample using cathode carbon blocks and graphite blocks, and the preparation of the control sample using graphite blocks, include: The cathode carbon block is processed into a carbon block column with a preset diameter and a first preset length, and the graphite block is processed into a first graphite column with a preset diameter and a second preset length. The carbon block column and the first graphite column are connected and fixed to obtain a composite sample of a third preset length; The graphite block is processed into a second graphite column with a preset diameter and a third preset length to obtain a control sample, wherein the third preset length is equal to the sum of the first preset length and the second preset length.

3. The method according to claim 2, characterized in that, The first preset length is 20mm to 50mm, the second preset length is 50mm to 80mm, and the third preset length is 100mm.

4. The method according to claim 1, characterized in that, Electrolysis of the composite sample includes: Place the corundum disc at the bottom of the graphite crucible and place the composite sample on the corundum disc, so that the composite sample is located in the center of the corundum disc. The electrolyte of a predetermined mass is evenly added into the inside of the graphite crucible, and the crucible lid and insulating ring on the top of the graphite crucible are assembled. The assembled graphite crucible is heated to a preset temperature under a preset pressure; Using the assembled graphite crucible as the anode and the composite sample as the cathode, electrolysis is performed at a preset current density for a preset duration.

5. The method according to claim 1, characterized in that, Electrolysis of the control sample includes: Place the corundum disc at the bottom of the graphite crucible and place the reference sample on the corundum disc, so that the reference sample is located in the center of the corundum disc. The electrolyte of a predetermined mass is evenly added into the inside of the graphite crucible, and the crucible lid and insulating ring on the top of the graphite crucible are assembled. The assembled graphite crucible is heated to a preset temperature under a preset pressure; Using the assembled graphite crucible as the anode and the control sample as the cathode, electrolysis is performed at a preset current density for a preset duration.

6. The method according to claim 4 or 5, characterized in that, The electrolyte comprises 71.5% by mass of Na3AlF6, 14.5% by mass of NaF, 5.0% by mass of CaF2, and 9.0% by mass of Al2O3.

7. The method according to claim 4 or 5, characterized in that, The preset temperature is 975℃ to 985℃, and the preset current density is 0.6A / cm². 2 Up to 0.8A / cm 2 The preset duration is 1.5h to 2.5h.

8. The method according to claim 2, characterized in that, The determination of the first length increment curve of the composite sample during electrolysis includes: The length increment of the composite sample at various moments during the electrolysis process is obtained to obtain the first length increment curve of the composite sample.

9. The method according to claim 2, characterized in that, The determination of the second length increment curve of the control sample during electrolysis includes: The length increment of the control sample at various moments during the electrolysis process is obtained to obtain the second length increment curve of the control sample.

10. The method according to claim 1, characterized in that, Determining the sodium expansion rate of the aluminum cathode based on the first length increment curve and the second length increment curve includes: The expansion rate curve of the aluminum cathode is determined by the following formula: in, The expansion rate curve of the aluminum cathode is shown. This represents the first length increment curve of the composite sample; This represents the second length increment curve of the control sample; Indicates the first preset length; Indicates the second preset length; The maximum value in the expansion rate curve of the aluminum cathode is taken as the sodium expansion rate of the aluminum cathode.

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