Method for improving impurity analysis precision of primary aluminum in laboratory-scale inert anode aluminum electrolysis

Abstract

The invention relates to a method for improving laboratory-scale inert anode aluminum electrolysis primary aluminum impurity analysis precision, and belongs to the technical field of primary aluminum impurity analysis. The method comprises the following steps: firstly, determining an introduction body of impurities in primary aluminum, and mass fractions of an impurity element A and a specific element M introduced by the introduction body; then determining the mass fractions of an impurity element A and a specific element M in the to-be-detected aluminum sample; and obtaining the actual content of the impurity element A in the to-be-detected aluminum sample according to a # imgabs0 # expression. According to the method, on the basis of the specific element M of the impurities, the actual content of the impurity A introduced in the electrolysis process of the electrolytic primary aluminum can be obtained by deducting the doping amount of other elements A in the impurities according to the proportion, and the problem that in a laboratory-scale inert anode aluminum electrolysis test, aluminum is discharged by adopting an aluminum discharging spoon and using measuring tools and instruments, and the measurement accuracy is low is effectively solved. And the problems of inaccurate primary aluminum impurity analysis result, large error, poor reproducibility and the like are solved.

Description

Technical Field

[0001] The present application relates to the technical field of primary aluminum quality analysis, and in particular to a method for improving the accuracy of impurity analysis of primary aluminum in laboratory-scale inert anode aluminum electrolysis. Background Art

[0002] Laboratory-scale inert anode aluminum electrolysis testing is a key component of inert anode aluminum electrolysis technology research. The impurity content of raw aluminum during electrolysis testing is a key indicator in inert anode material research. The level of impurity content in raw aluminum is an important factor in measuring the corrosion resistance of inert anodes and calculating corrosion rates. Therefore, accurately measuring the impurity content of raw aluminum during electrolysis is crucial for inert anode material research.

[0003] However, laboratory-scale inert anode aluminum electrolysis experiments produce relatively low primary aluminum output. For example, a 100A electrolysis experiment yields approximately 0.725 kg of primary aluminum per day. Limited by the size of the electrolytic cell, the molten aluminum in the cell is only a few centimeters high. Given this low molten aluminum level and limited daily output, manual scooping with a ladle is more suitable. Due to the limitations of the electrolytic cell and the ladle's dimensions, each tapping requires dozens of repetitions. This repeated scooping process often presents two problems: First, the tapping process inevitably stirs the molten aluminum and electrolyte layers, causing alumina and electrolyte to be carried over into the scooped aluminum. Once poured into the aluminum storage container, the molten aluminum rapidly solidifies, preventing the aluminum from being fused. Consequently, the electrolyte and alumina carried over from each scoop cannot be separated and become intermingled, resulting in a pronounced layering of the raw aluminum ingot, which can interfere with subsequent sampling and analysis. Second, the scoop is easily corroded by the molten aluminum after repeated and prolonged tapping. Metallic impurities from the scoop enter the molten aluminum, resulting in an inflated impurity analysis result. Furthermore, other measuring instruments, such as thermocouples, electrolyte melts, and molten aluminum height gauges, can also corrode over time, affecting the impurity analysis results. Consequently, these issues significantly impact the accuracy of raw aluminum impurity analysis, increasing errors, reducing reproducibility, or even completely eliminating reproducibility.

[0004] In addition, after the aluminum liquid is scooped into the aluminum storage container, impurities will segregate during the solidification process. Especially when the amount of aluminum is large, the impurities will segregate to the post-solidification area. This will lead to significant differences in impurity content when sampling from different areas of the original aluminum ingot, even if no obvious inclusions such as alumina and electrolyte are observed in the samples. Summary of the Invention

[0005] The present application provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis to solve the following technical problem: how to improve the accuracy of impurity analysis of raw aluminum.

[0006] The present invention provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0007] Determining the impurity introduction body of the original aluminum and the mass fraction of the impurity element A and the unique element M introduced by the introduction body;

[0008] Obtaining an aluminum sample to be tested from the raw aluminum, and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested;

[0009] Obtaining the actual content of the impurity element A in the aluminum sample to be tested based on the mass fractions of the impurity element A and the unique element M in the introduced body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested;

[0010] According to the mass fractions of the impurity element A and the unique element M of the introduced body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested, the expression for obtaining the actual content of the impurity element A in the aluminum sample to be tested is:

[0011]

[0012] In the formula, b represents the actual content of impurity element A in the aluminum sample to be tested, a represents the mass fraction of impurity element A in the aluminum sample to be tested, m represents the mass fraction of unique element M in the aluminum sample to be tested, [A] represents the mass fraction of impurity element A introduced by the introducer, and [M] represents the mass fraction of unique element M introduced by the introducer.

[0013] Optionally, the selection of the unique element M includes any of the following situations:

[0014] If the introduced substance contains a certain element alone, then the element is the unique element M of the introduced substance;

[0015] If the introduced body contains multiple elements alone, then the element with the highest mass fraction among the multiple elements in the aluminum sample to be tested is selected as the unique element M.

[0016] Optionally, obtaining an aluminum sample to be tested by using the raw aluminum and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested specifically includes:

[0017] Obtaining an aluminum sample to be tested by using the raw aluminum;

[0018] The aluminum sample to be tested is subjected to elemental analysis to obtain the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested.

[0019] Optionally, obtaining the aluminum sample to be tested from the raw aluminum specifically includes:

[0020] preparing an original aluminum ingot using the original aluminum as a raw material;

[0021] remelting the original aluminum ingot to obtain a remelted sample ingot;

[0022] An aluminum sample is extracted from the remelted sample ingot to obtain an aluminum sample to be tested.

[0023] Optionally, remelting the original aluminum ingot to obtain a remelted ingot sample comprises:

[0024] Melting the original aluminum ingot to obtain aluminum liquid;

[0025] The aluminum liquid is stirred, allowed to stand, and then scum is removed;

[0026] The aluminum liquid after removing the scum is cooled to obtain a remelted sample ingot.

[0027] Optionally, the melting container or cooling container is a graphite crucible;

[0028] Optionally, a graphite stirring rod is used to stir the aluminum liquid.

[0029] Optionally, extracting the aluminum sample from the remelted ingot specifically includes: extracting the aluminum sample from a central area of the remelted ingot.

[0030] Optionally, the impurity element A refers to an element whose mass fraction in the introduced body exceeds 0.03%.

[0031] Optionally, the method further includes: if the aluminum sample to be tested includes impurity element N and the introduced body does not contain impurity element N, then the mass fraction n of the impurity element N is the actual content of the impurity element N.

[0032] Optionally, the introduction body includes at least one of the following: an aluminum tapping spoon, a temperature measuring thermocouple sleeve, an electrolyte melt, and an aluminum liquid height measuring rod.

[0033] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0034] The present application provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis. The method first determines the introduction body of impurities in the raw aluminum and the mass fractions of the impurity element A and the unique element M introduced by the introduction body; then, an aluminum sample to be tested is obtained from the raw aluminum, and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested are determined; based on the mass fractions of the impurity element A and the unique element M of the introduction body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested, the actual content of the impurity element A in the aluminum sample to be tested is obtained; based on the unique element M of the impurity, the method proportionally deducts the amount of other elements A added to the impurity, and thus the actual content of impurity A introduced by the raw aluminum during the electrolysis process can be obtained.

[0035] This method effectively addresses the issues of slag inclusion, additional metallic impurities, and impurity segregation in primary aluminum ingots caused by the use of a tapping spoon and measuring instruments in laboratory-scale inert anode aluminum electrolysis experiments. These issues can lead to inaccurate primary aluminum impurity analysis results, large errors, and poor reproducibility. This method accurately and objectively reflects the quality of primary aluminum produced in laboratory-scale inert anode aluminum electrolysis experiments. Since impurities in the primary aluminum originate almost exclusively from the inert electrode, it also reflects the quality of the inert electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 A flow chart of a method for improving the accuracy of impurity analysis of raw aluminum in inert anode aluminum electrolysis on a laboratory scale according to some embodiments of the present application;

[0039] Figure 2 Schematic diagram of aluminum tapping from an electrolytic cell and obtaining raw aluminum ingots according to some embodiments of the present application;

[0040] In the figure, 1-the shell of the experimental electrolytic cell; 2-the aluminum liquid at the bottom of the electrolytic cell; 3-the aluminum tapping spoon; 4-the aluminum tapping trough; 5-the aluminum storage container; 6-the original aluminum ingot formed by the solidification of the aluminum liquid;

[0041] Figure 3 A schematic diagram of preparing a thin-diameter cylindrical remelted ingot by remelting an original aluminum ingot according to some embodiments of the present application;

[0042] In the figure, 7-sampling spoon; 8-graphite crucible; 9-corundum crucible; 10-remelted aluminum liquid; 11-heating coil; 12-thin-diameter sampling crucible; 13-thin-diameter sample sampling part. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. All other embodiments that can be implemented by ordinary technicians in this field based on the embodiments of the present application should be considered as part of the scope of protection of this application.

[0044] The range descriptions described in this article, such as numerical ranges, ratio ranges, etc., include all possible sub-ranges and single numerical values within the range. For example, the range description of "1 to 6" or "1~6" covers all sub-ranges from 1 to 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including", "comprising", etc. used in this article mean "including but not limited to"; relational terms such as "first" and "second" are only used to distinguish different entities or operations, and do not imply an actual sequence or association relationship; "and / or" means that multiple situations can exist alone or at the same time; expressions such as "at least one", "multiple", and "at least one" refer to any combination of corresponding objects, including a combination of single or multiple objects. The proportional relationships involved in the article, such as mass ratios, molar ratios, etc., should be understood as the corresponding relationship between the first and second terms of the proportional formula in the order of description. The raw materials, reagents, instruments and equipment used in this article can be purchased on the market or prepared by existing methods.

[0045] Figure 1 A schematic flow chart of a method for improving the accuracy of impurity analysis of raw aluminum in inert anode aluminum electrolysis on a laboratory scale according to some embodiments of the present application;

[0046] The laboratory-scale inert anode aluminum electrolysis described in this application refers to an aluminum electrolysis test carried out in a laboratory, in which the electrolytic cell requires external heating, the electrolytic cell capacity is between 20A and 2kA, and the aluminum liquid in the electrolytic cell can be scooped out with an aluminum spoon.

[0047] like Figure 1 As shown, the embodiment of the present application provides a method for improving the accuracy of impurity analysis of raw aluminum in inert anode aluminum electrolysis on a laboratory scale, comprising the following steps:

[0048] S1. Determining the impurity introduction body of the original aluminum and the mass fractions of the impurity element A and the unique element M introduced by the introduction body;

[0049] The purpose of step S1 is to first determine the sources of impurities introduced into raw aluminum during laboratory-scale inert anode aluminum electrolysis. These include equipment encountered during the production process, corrosion of the inert anode, corrosion of the aluminum tapping spoon, and measuring instruments. The materials of each impurity introducing source and the types of elements they contain are then determined, allowing the presence and corresponding mass fractions of various impurity elements A and unique elements M in the material to be determined. Elements A and M can be any element, such as Cr, Ni, Cu, etc.

[0050] S2. Obtaining an aluminum sample to be tested from the raw aluminum, and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested;

[0051] In step S2, an aluminum sample to be tested is first prepared from raw aluminum to obtain an aluminum sample for element mass fraction determination, which is used to determine the mass fraction of each element in the aluminum sample to be tested, thereby calculating the mass fraction of the unique element M and any impurity element A, providing data for subsequent calculations.

[0052] S3. According to the mass fractions of the impurity element A and the unique element M of the introduced body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested, the actual content of the impurity element A in the aluminum sample to be tested is obtained. The expression used is:

[0053]

[0054] In the formula, b represents the actual content of impurity element A in the aluminum sample to be tested, a represents the mass fraction of impurity element A in the aluminum sample to be tested, m represents the mass fraction of unique element M in the aluminum sample to be tested, [A] represents the mass fraction of impurity element A introduced by the introducer, and [M] represents the mass fraction of unique element M introduced by the introducer.

[0055] The purpose of step S3 is to deduct a certain element M contained alone in the impurity introduction body from the original impurity analysis results based on the content value of the specific element M in the aluminum sample to be tested, and to calculate the content of the impurity element A introduced from the impurity introduction body based on the mass fraction ratio of the element M contained alone to other impurity elements A in the impurity introduction body. By deducting its content, the actual content of the impurity element A in the original aluminum is obtained.

[0056] This method effectively addresses the issues of slag inclusion, additional metallic impurities, and impurity segregation in primary aluminum ingots caused by the use of a tapping spoon and measuring instruments in laboratory-scale inert anode aluminum electrolysis experiments. These issues can lead to inaccurate primary aluminum impurity analysis results, large errors, and poor reproducibility. This method accurately and objectively reflects the quality of primary aluminum produced in laboratory-scale inert anode aluminum electrolysis experiments. Since impurities in the primary aluminum originate almost exclusively from the inert electrode, it also reflects the quality of the inert electrode.

[0057] As an optional implementation manner, the selection of the unique element M includes any of the following situations:

[0058] If the introduced body contains a certain element alone, then the element is the unique element M of the introduced body; for example, the aluminum spoon is made of 310S stainless steel, which contains metallic Cr element, while the inert anode and other impurity introduced bodies do not contain metallic Cr element, then metallic Cr is the unique element M.

[0059] If the introduced body contains multiple elements, the element with the highest mass fraction among the multiple elements in the aluminum sample to be tested is selected as the unique element M. For example, if the measuring tool contains metallic Cr and Mn elements, but the inert anode does not contain metallic Cr and Mn elements, and the impurity element analysis results of the aluminum sample to be tested show that the Cr content is higher than the Mn content, then metallic Cr is the unique element M.

[0060] As an optional embodiment, obtaining an aluminum sample to be tested from the raw aluminum and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested specifically includes:

[0061] S31, obtaining an aluminum sample to be tested by using the raw aluminum;

[0062] The purpose of step S31 is to use raw aluminum as raw material to provide an aluminum sample to be tested with uniform composition and small error.

[0063] S32. Perform elemental analysis on the aluminum sample to be tested to obtain the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested.

[0064] In step S32, element analysis is performed on the aluminum sample to be tested, with the purpose of obtaining the mass fraction of each element. The test analysis method adopted may be inductively coupled plasma atomic emission spectrometry, etc.

[0065] In the above embodiment, by obtaining an aluminum sample to be tested with uniform composition, elemental analysis is performed on the aluminum sample to be tested, and the original elemental analysis result of the aluminum sample to be tested is accurately obtained to provide data support for subsequent calculations.

[0066] As an optional embodiment, obtaining the aluminum sample to be tested from the raw aluminum specifically includes:

[0067] S311, preparing an original aluminum ingot using the raw aluminum as a raw material;

[0068] The purpose of step S311 is to first obtain the ingot of the original aluminum liquid to be tested after cooling as the raw material, and the preparation method can be as follows: Figure 2 The device described in the above method uses a metal aluminum spoon to transfer aluminum liquid from a laboratory-scale inert anode aluminum electrolytic cell into an aluminum storage container according to a set aluminum discharge weight. The aluminum liquid is naturally cooled and solidified in the aluminum storage container to obtain a raw aluminum ingot:

[0069] S312, remelting the original aluminum ingot to obtain a remelted sample ingot;

[0070] Since the original aluminum ingot may be segregated and contain more impurities, sampling directly from the original aluminum ingot may result in deviations. Therefore, the purpose of step S312 is to avoid the above situation and remelt the original aluminum ingot.

[0071] S313. Extracting an aluminum sample from the remelted ingot to obtain an aluminum sample to be tested.

[0072] In the above embodiment, the obtained remelted ingot is usually a thin diameter high cylindrical ingot. The reason is that the thin diameter cylindrical ingot cools faster, and other metal impurities do not have time to segregate, so the composition is naturally more uniform.

[0073] As an optional embodiment, the original aluminum ingot is remelted to obtain a remelted ingot sample, which specifically includes:

[0074] Melting the original aluminum ingot to obtain aluminum liquid;

[0075] Stirring the aluminum liquid, allowing it to stand, and removing scum;

[0076] The aluminum liquid after removing the scum is placed in a graphite crucible with a small diameter for cooling to obtain a remelted sample ingot.

[0077] In the above embodiment, by remelting, stirring, and keeping the original aluminum ingot warm, the entrained alumina and electrolyte can float to form slag. After the slag is removed, the influence of alumina and electrolyte slag on sampling and impurity analysis can be eliminated.

[0078] The temperature range of the heat preservation and standing is 720°C to 750°C, and the time is extended from 5 minutes to 8 minutes; the inner diameter of the small-diameter graphite crucible is 1.5 cm to 3 cm; the cooling method can be natural cooling or forced cooling, wherein the natural cooling is cooling at room temperature and in air; the forced cooling is blowing / water cooling.

[0079] As an optional embodiment, the melting container or the cooling container is a graphite crucible.

[0080] As an optional implementation, a graphite stirring rod is used to stir the aluminum liquid.

[0081] In the above embodiment, in order to avoid the introduction of impurities during the remelting process, a graphite crucible and a graphite stirring rod are used as tools.

[0082] As an optional embodiment, the extracting of the aluminum sample from the remelted ingot specifically includes: extracting the aluminum sample from the middle region of the remelted ingot.

[0083] In the above embodiment, sampling from the middle can ensure that the aluminum sample has a uniform composition. And the position is fixed, which allows for better repeatability of experiments.

[0084] As an optional embodiment, the middle portion of the thin-diameter cylindrical ingot specifically refers to the midpoint in the height direction, and aluminum chips need to be drilled from the side wall of the cylindrical ingot.

[0085] As an optional embodiment, when remelting the original aluminum ingot, a graphite crucible is used to melt the original aluminum ingot; and / or a graphite stirring rod is used to stir the aluminum liquid.

[0086] As an optional implementation manner, the unique element M includes any of the following situations:

[0087] If impurities of different materials contain a certain element separately, then this element is the unique element M; for example, the aluminum spoon is made of 310S stainless steel, which contains metallic Cr, while the inert anode does not contain metallic Cr, so metallic Cr is the unique element M.

[0088] If impurities of different materials contain multiple elements, the element with the highest content in the aluminum sample elemental analysis results is selected as the unique element M. For example, if the measuring tool contains metallic Cr and Mn, but the inert anode does not contain metallic Cr and Mn, and the initial impurity analysis results show that the Cr content is higher than the Mn content, then metallic Cr is the unique element M.

[0089] As an optional embodiment, the element A refers to an element whose content in the impurities exceeds 0.03%.

[0090] In the above embodiment, because the content of trace metal elements in the aluminum liquid is lower, conventional analytical detection equipment, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES), is inaccurate in trace element analysis and may result in large analytical errors. Therefore, trace elements with a content below 0.03% do not need to be considered.

[0091] As an optional embodiment, the method further includes: if the aluminum sample to be tested includes impurity element N and the introduced body does not contain impurity element N, then the mass fraction n of the impurity element N is the actual content of the impurity element N.

[0092] In the above embodiment, if the aluminum sample to be tested includes impurity element N, but all known introduction bodies do not include this impurity element, it indicates that the impurity element N is not introduced through the introduction body, so there is no need to recalculate its mass fraction, that is, the mass fraction n of the impurity element N obtained by the test is the actual content of the impurity element N.

[0093] As an optional embodiment, the impurity introduction body at least includes an aluminum spoon, a temperature measuring thermocouple sleeve, an electrolyte melt and an aluminum liquid height measuring rod.

[0094] In the above embodiment, if the elements of the above introduction are different, it is necessary to use the expression for each introduction separately. Calculate the actual content of impurity element A; if in the raw aluminum preparation process, the aluminum spoon, temperature measuring thermocouple sleeve, electrolyte melt and aluminum liquid height measuring rod are made of the same material, the metal element type and content ratio of the aluminum spoon can represent all measuring tools, and only the expression Calculate the actual content of impurity element A.

[0095] All types of metal elements contained in the inert anode material and the aluminum tapping spoon material mentioned in the embodiments of the present application are known data, and at least one of the metal elements contained in the aluminum tapping spoon material is not present in the inert anode material; the content and ratio of the metal elements contained in the aluminum tapping spoon material are known data, or are measured data by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis.

[0096] It should be noted that when determining the source of impurities, since the inert anode is a necessary equipment in the process of preparing primary aluminum, the impurities introduced by the inert anode are necessary impurities in the preparation of primary aluminum and do not need to be removed.

[0097] As an optional embodiment, the aluminum liquid in the electrolytic cell is produced by molten salt electrolysis, and the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used in the electrolysis process will not introduce metal impurities into the aluminum liquid during the molten salt electrolysis process.

[0098] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0099] Example 1

[0100] This embodiment provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0101] S1. During laboratory 100A inert anode aluminum electrolysis tests, the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used did not introduce metallic impurities into the molten aluminum during the molten salt electrolysis process. Impurities in raw aluminum primarily come from corrosion of the inert anode, the tapping ladle, and measuring instruments.

[0102] The aluminum spoon and measuring tools are made of 310S stainless steel, the main components of which are Ni:Fe:Cr. The main components of the inert anode material are Ni, Fe, and Cu, and do not contain Cr. Therefore, the unique element in the aluminum spoon and measuring tools is Cr, with a mass fraction of up to 25%.

[0103] S2. The mass fraction of Ni in the aluminum spoon and the measuring tool was determined by inductively coupled plasma emission spectrometry to be 20%, and the mass fraction of Fe was 55%.

[0104] S31. Obtain the aluminum sample to be tested:

[0105] According to the set aluminum output weight of 0.72kg, the aluminum liquid in the laboratory-scale inert anode aluminum electrolytic cell was taken into a high-purity graphite crucible, and the aluminum liquid was naturally cooled and solidified in the high-purity graphite crucible to obtain the original aluminum ingot. Figure 1 shown.

[0106] Place the original ingot into a dry, clean corundum crucible and place it together in a melting furnace with a crucible made of high-purity graphite for remelting. Use stirring and slag removal tools made of high-purity graphite to manually stir the melt and remove the slag attached to the surface of the melt. During the stirring and slag removal process, be careful not to cause the melt to roll over to avoid secondary oxidation of the melt and the introduction of an oxide layer. Then keep it warm at 720°C and let it stand for 8 minutes. Subsequently, use a graphite sampling spoon to pour part of the aluminum liquid into a graphite crucible with a diameter of 1.5 cm. After it cools naturally, a small cylindrical aluminum ingot will be formed. Figure 2 The thin-diameter cylindrical ingot was taken out of the graphite crucible, and an electric drill was used to drill about 0.2 grams of aluminum chips from the center of the cylindrical aluminum ingot for subsequent impurity analysis.

[0107] S32. Obtain the elemental analysis results of the aluminum sample to be tested, and list the detailed data in Table 1.

[0108] S4. Using the formula, the content of Fe element in the aluminum sample to be tested is calculated to be 0.1756 (calculation process: 0.422-0.112 / 0.25*0.55), and the content of Ni is calculated to be 0.0084 (0.098-0.112 / 0.25*0.20). The results are equal. All data are listed in Table 1.

[0109] Example 2

[0110] This embodiment provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0111] S1. During laboratory 100A inert anode aluminum electrolysis testing, the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used did not introduce metallic impurities into the molten aluminum during the molten salt electrolysis process. However, impurities in raw aluminum are primarily associated with corrosion of the inert anode, the tapping ladle, and measuring instruments. These impurities are directly linked to excessive anode oxidation and slagging during the aluminum electrolysis process. Some impurities affect economic and technical indicators such as the electrolytic cell's current efficiency and aluminum purity.

[0112] The aluminum tapping spoon and measuring tools are made of 316L stainless steel that meets the ASTM A240 standard. Its main components are Ni, Fe, Cr, and Mo, with Cr content of 17.00% and Mo content of 2.00% to 3.00%. The inert anode material mainly contains Ni, Fe, and Cu, and does not contain Cr or Mo. According to the results of impurity element analysis, the Cr content is higher than Mo. Therefore, the unique element of the aluminum tapping spoon and measuring tools is Cr, with a mass fraction of 17%.

[0113] S2. The mass fraction of the element Ni in the aluminum spoon and measuring tools is 12%, which meets the 316L stainless steel standard, and the mass fraction of the element Fe is 69%, which also meets the standard.

[0114] S31. Obtain the aluminum sample to be tested:

[0115] According to the set aluminum output weight of 1.45kg, the aluminum liquid in the laboratory-scale inert anode aluminum electrolytic cell was taken into a high-purity graphite crucible, and the aluminum liquid was naturally cooled and solidified in the high-purity graphite crucible to obtain the original aluminum ingot. Figure 1 shown.

[0116] The original ingot is placed in a dry and clean corundum crucible, and then moved as a whole to a high-purity graphite melting furnace for remelting. Afterwards, use a special high-purity graphite stirring and slag removal tool to carefully stir the melt and carefully remove the scum on its surface. During the stirring and slag removal process, be careful not to cause the melt to roll over to avoid secondary oxidation of the melt and the introduction of an oxide layer. Then keep it at 725°C and let it stand for 7 minutes. Then use a graphite sampling spoon to pour part of the aluminum liquid into a 2cm diameter graphite crucible and air cool it to form a thin diameter cylindrical ingot. Figure 2 The thin diameter cylindrical ingot was taken out from the graphite crucible, and 0.4 g of aluminum chips were drilled out from the middle of the thin diameter cylindrical ingot using an electric drill to serve as the aluminum sample to be used for impurity analysis.

[0117] S32. Obtain the elemental analysis results of the aluminum sample to be tested, see Table 1 for details.

[0118] S4. According to the formula, the Fe content in the aluminum sample to be tested is 0.0809 (calculation process: 0.430-0.086 / 0.17×0.69), and the Ni content is 0.0682 (calculation process: 0.129-0.086 / 0.17×0.12); see Table 1 for specific results.

[0119] Example 3

[0120] This embodiment provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0121] S1. During the laboratory 100A inert anode aluminum electrolysis test, the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used will not introduce metal impurities into the aluminum liquid during the molten salt electrolysis process. The impurities in the original aluminum are mainly corrosion of the inert anode, corrosion of the aluminum spoon, and corrosion of measuring tools.

[0122] The aluminum spoon and measuring tools are made of 310S stainless steel, the main components of which are Ni:Fe:Cr; the main components of the inert anode material are Ni, Fe, and Cu, and do not contain Cr. Therefore, the unique element of the aluminum spoon and measuring tools is Cr, and its mass fraction is 25%.

[0123] S2. It was determined that the mass fraction of Ni element in the aluminum spoon and measuring tools was 20%, and the mass fraction of Fe element was 55%.

[0124] S31, obtaining an aluminum sample to be tested;

[0125] According to the set aluminum output weight of 1.45 kg, the aluminum liquid in the laboratory-scale inert anode aluminum electrolytic cell was taken into a high-purity graphite crucible. The aluminum liquid was naturally cooled and solidified in the high-purity graphite crucible to obtain the original aluminum ingot.

[0126] Place the original ingot in a dry and clean corundum crucible, and then place it in a high-purity graphite melting furnace for remelting. Use a stirring and slag removal tool made of high-purity graphite to manually stir the melt and remove the slag on its surface. During the stirring and slag removal process, be careful not to cause the melt to roll over to avoid secondary oxidation of the melt and the introduction of an oxide layer. Then, keep it at 743°C and let it stand for 6 minutes. Then use a graphite sampling spoon to pour part of the aluminum liquid into a 2.5cm diameter graphite crucible and air-cool it to form a thin diameter cylindrical ingot. Figure 2 The thin diameter cylindrical ingot was taken out of the graphite crucible, and 0.3 g of aluminum chips were drilled from the center of the thin diameter cylindrical ingot using an electric drill to serve as the aluminum sample to be used for impurity analysis.

[0127] S32, obtaining the elemental analysis results of the aluminum sample to be tested, as shown in Table 1;

[0128] S4. Using the formula, the Fe content in the aluminum sample to be tested was calculated to be 0.1756 (calculation process: 0.422-0.112 / 0.25*0.55), and the Ni content was 0.0084 (calculation process: 0.098-0.112 / 0.25*0.20); the results are shown in Table 1.

[0129] Example 4

[0130] This embodiment provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0131] S1. During the laboratory 100A inert anode aluminum electrolysis test, the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used will not introduce any metal impurities into the aluminum liquid during the molten salt electrolysis process. The impurities in the raw aluminum are mainly corrosion of the inert anode, corrosion of the aluminum spoon, and corrosion of measuring tools.

[0132] The aluminum spoon and measuring tools are made of 316L stainless steel, whose main components are nickel, iron, chromium, and molybdenum, with a chromium content of 17%. 316L stainless steel is a high-quality stainless steel alloy widely used in industries such as food and pharmaceuticals, marine engineering, chemical industry, and oil and gas extraction. It has excellent corrosion resistance, high-temperature strength, and wear resistance. The inert anode material mainly contains nickel, iron, and copper, and does not contain chromium or molybdenum.

[0133] S2. The mass fraction of Ni in the aluminum spoon and measuring tools is 12%, and the mass fraction of Fe is 69%;

[0134] S31. Obtain the aluminum sample to be tested:

[0135] According to the set aluminum output weight of 0.72 kg, the aluminum liquid in the laboratory-scale inert anode aluminum electrolytic cell was taken into a high-purity graphite crucible. The aluminum liquid was naturally cooled and solidified in the high-purity graphite crucible to obtain the original aluminum ingot.

[0136] The original ingot was placed in a dry and clean corundum crucible and then remelted in a high-purity graphite furnace. The melt was manually stirred and slag removed using stirring and slag removal tools made of high-purity graphite. Care was taken to prevent the melt from rolling during the stirring and slag removal process to prevent secondary oxidation and the introduction of an oxide layer. The ingot was then held at 730°C for 7 minutes. A portion of the molten aluminum was then poured into a 2cm diameter graphite crucible using a graphite sampling spoon and air-cooled to form a thin cylindrical ingot. The cylindrical ingot was carefully removed from the graphite crucible, and 0.4g of aluminum chips were precisely drilled from its center using an electric drill for subsequent impurity analysis.

[0137] S32, obtaining the elemental analysis results of the aluminum sample to be tested, as shown in Table 1;

[0138] S4. Using the formula, the Fe content in the aluminum sample to be tested was calculated to be 0.1086 (calculation process: 0.409-0.074 / 0.17*0.69), and the Ni content was 0.0437 (calculation process: 0.096-0.074 / 0.17*0.12); the results are shown in Table 1.

[0139] Example 5

[0140] This embodiment provides a method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, comprising the following steps:

[0141] S1. During the laboratory 100A inert anode aluminum electrolysis test, the alumina, electrolyte, cathode, and electrolytic cell furnace lining materials used will not introduce metal impurities into the aluminum liquid during the molten salt electrolysis process. The impurities in the original aluminum are mainly corrosion of the inert anode, corrosion of the aluminum spoon, and corrosion of measuring tools.

[0142] The aluminum spoon and measuring tools are made of 310S stainless steel, whose chemical composition mainly includes elements such as carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr) and nickel (Ni). Specifically, the chromium (Cr) content of 310S stainless steel is 24.00% to 26.00%, and the nickel (Ni) content is 19.00% to 22.00%. The main components of inert anode materials are Ni, Fe, and Cu, and do not contain Cr. Therefore, the unique element of the aluminum spoon and measuring tools is Cr, and its mass fraction is between 24.00% and 26.00%.

[0143] S2. The mass fraction of Ni in the aluminum spoon and measuring tools is 20%, and the mass fraction of Fe is 55%;

[0144] S31, obtaining an aluminum sample to be tested;

[0145] According to the set aluminum output weight of 1.45 kg, the aluminum liquid in the laboratory-scale inert anode aluminum electrolytic cell was taken into a high-purity graphite crucible. The aluminum liquid was naturally cooled and solidified in the high-purity graphite crucible to obtain the original aluminum ingot.

[0146] Place the original ingot in a dry and clean corundum crucible, and then place it in a high-purity graphite melting furnace for remelting. Use stirring and slag removal tools made of high-purity graphite to manually stir the melt and remove the slag attached to the surface of the melt. During the stirring and slag removal process, be careful not to cause the melt to roll over to avoid secondary oxidation of the melt and the introduction of an oxide layer. Then keep it at 750°C and let it stand for 5 minutes. Then use a graphite sampling spoon to pour part of the aluminum liquid into a 3cm diameter graphite crucible and air-cool it to form a thin diameter cylindrical ingot. Figure 2 The thin diameter cylindrical ingot was taken out from the graphite crucible, and 0.5 g of aluminum chips were drilled out from the middle of the thin diameter cylindrical ingot using an electric drill to serve as the aluminum sample to be used for impurity analysis.

[0147] S32, obtaining the elemental analysis results of the aluminum sample to be tested, as shown in Table 1;

[0148] S4. According to the experimental steps of aluminum atomic absorption spectrometry, the content of iron in the aluminum sample to be tested was calculated to be 0.1422, and the content of nickel was 0.0188. Detailed results are shown in Table 1.

[0149] Comparative Example 1

[0150] The method of this comparative example is the same as that of Example 1, except that 0.4 g of the sample is directly taken from the middle part of the original aluminum ingot as the aluminum sample to be tested. The results are shown in Table 1.

[0151] Comparative Example 2

[0152] The method of this comparative example is the same as that of Example 2, except that Mo is used as the unique element of the aluminum tapping spoon. The results are shown in Table 1.

[0153] Comparative Example 3

[0154] The method of this comparative example is the same as that of Example 5, except that forced cooling is not used when making a thin cylindrical sample ingot with a diameter of 3 cm, and 0.5 g of aluminum chips are drilled out from the bottom of the thin cylindrical sample ingot as an aluminum sample to be used for impurity analysis. The results are shown in Table 1.

[0155] Table 1 Statistics of impurity analysis results of aluminum samples in Examples 1 to 5 and Comparative Examples 1 to 3

[0156]

[0157] Based on references 1 and 3, studies of the distribution coefficients of impurity elements such as Fe and Si in raw aluminum and the application of ICP-MS technology have shown that even when using the same processing tools, such as the aluminum ladle, raw aluminum impurity analysis results can vary significantly. However, by adopting specific impurity removal methods, impurity interference can be significantly reduced, resulting in more consistent and accurate impurity analysis results.

[0158] In summary, the method provided in this application for improving the accuracy of raw aluminum impurity analysis in laboratory-scale inert anode aluminum electrolysis effectively addresses the problems encountered in laboratory-scale inert anode aluminum electrolysis experiments, such as slag inclusions, additional metallic impurities, and impurity segregation in the raw aluminum ingots, which are caused by the use of aluminum spoons and measuring tools. These problems result in inaccurate raw aluminum impurity analysis results, large errors, and poor reproducibility. Furthermore, the method can effectively distinguish impurities in different materials and provide more accurate results when evaluating the corrosion resistance of inert electrodes.

[0159] The foregoing is merely a detailed description of the present invention, intended to enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but rather is intended to conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for improving the accuracy of impurity analysis of raw aluminum in laboratory-scale inert anode aluminum electrolysis, characterized in that: The following steps are involved: Determining the impurity introduction body of the original aluminum and the mass fraction of the impurity element A and the unique element M introduced by the introduction body; Obtaining an aluminum sample to be tested from the raw aluminum, and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested; Obtaining the actual content of the impurity element A in the aluminum sample to be tested based on the mass fractions of the impurity element A and the unique element M in the introduced body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested; According to the mass fractions of the impurity element A and the unique element M of the introduced body and the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested, the expression for obtaining the actual content of the impurity element A in the aluminum sample to be tested is: In the formula, b represents the actual content of impurity element A in the aluminum sample to be tested, a represents the mass fraction of impurity element A in the aluminum sample to be tested, m represents the mass fraction of unique element M in the aluminum sample to be tested, [A] represents the mass fraction of impurity element A introduced by the introducer, and [M] represents the mass fraction of unique element M introduced by the introducer.

2. The method according to claim 1, characterized in that The selection of the unique element M includes any of the following situations: If the introduced substance contains a certain element alone, then the element is the unique element M of the introduced substance; If the introduced body contains multiple elements alone, then the element with the highest mass fraction among the multiple elements in the aluminum sample to be tested is selected as the unique element M.

3. The method according to claim 1, characterized in that The step of obtaining an aluminum sample to be tested from the raw aluminum and determining the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested specifically includes: Obtaining an aluminum sample to be tested by using the raw aluminum; The aluminum sample to be tested is subjected to elemental analysis to obtain the mass fractions of the impurity element A and the unique element M in the aluminum sample to be tested.

4. The method according to claim 2, characterized in that Obtaining the aluminum sample to be tested by using the raw aluminum specifically includes: preparing an original aluminum ingot using the original aluminum as a raw material; remelting the original aluminum ingot to obtain a remelted sample ingot; An aluminum sample is extracted from the remelted ingot to obtain an aluminum sample to be tested.

5. The method according to claim 3, characterized in that Remelting the original aluminum ingot to obtain a remelted ingot sample specifically comprises: Melting the original aluminum ingot to obtain aluminum liquid; Stirring the aluminum liquid, allowing it to stand, and removing scum; The aluminum liquid after removing the scum is cooled to obtain a remelted sample ingot.

6. The method according to claim 5, characterized in that The melting container or cooling container is a graphite crucible; and / or the aluminum liquid is stirred using a graphite stirring rod.

7. The method according to claim 3, characterized in that The extracting of the aluminum sample from the remelted ingot specifically includes: extracting the aluminum sample from the middle area of the remelted ingot.

8. The method according to claim 1, characterized in that The impurity element A refers to an element whose mass fraction in the introduced body exceeds 0.03%.

9. The method according to claim 1, characterized in that The method further includes: if the aluminum sample to be tested includes impurity element N and the introduced body does not contain impurity element N, then the mass fraction n of the impurity element N is the actual content of the impurity element N.

10. The method according to claim 1, characterized in that The introducing body comprises at least one of the following: an aluminum tapping spoon, a temperature measuring thermocouple sleeve, an electrolyte melt and an aluminum liquid height measuring rod.

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