Sample unit and method for a sampling system for sampling a sample from molten aluminum in a primary aluminum production facility

Abstract

The present invention relates to sample units of a sampling system for sampling a sample from a molten aluminum bath in a primary aluminum production facility. These sample units include a refractory body, a sample chamber assembly disposed within the refractory body, an inflow opening in flow connection with the sample chamber and positioned to connect with a lateral side of the sample chamber, and an inflow conduit at least partially disposed in the inflow opening. The present invention also relates to a sampling system and method for sampling a sample of molten aluminum with the sample units of the present invention.

Description

[0001] This invention relates to a sample unit of a sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility. The invention also relates to a sampling system comprising the sample unit of this invention and a method for taking samples from molten aluminum.

[0002] During the processing of metals in their molten state, it is necessary to obtain representative samples of the molten metal at various stages of the processing, for example, to analyze or evaluate the chemical composition or metallographic structure of the samples. Various methods for analyzing molten metals during manufacturing and further processing are known in the art.

[0003] Historically, the composition of solidified metal samples has often been determined using arc spark optical emission spectrometry (spark OES). Spark OES systems are effective for determining the chemical composition of metal samples and for controlling the processing of molten metals due to their rapid analysis time and inherent accuracy. Recently, LIBS spectroscopy has also been applied to obtain data of interest.

[0004] Regardless of the type of analysis, it is known that the accuracy and reliability of the results depend on the quality of the sample. Ideally, the sample should be analyzed without any further preparation steps and as close as possible to the sampling site.

[0005] There is a difference between primary aluminum (Al) production and recycled aluminum production: Primary aluminum is produced from Al raw materials (usually bauxite), which are chemically processed to obtain alumina, while recycled Al is produced from recycled Al waste or from primary aluminum that has undergone further processing, alloying, and / or remelting. For recycled aluminum production, the waste is melted in a suitable furnace and further processed and treated as needed.

[0006] Primary aluminum is typically produced via the Hall-Héroult process. This electrolytic process is based on the electrochemical decomposition of alumina dissolved in sodium cryolite electrolyte (Na3AlF6) at 940°C to 980°C. The process is multivariable and requires careful control of electrolyte chemistry, electrical input, and electrodes to achieve high efficiency and the correct chemical composition of the aluminum metal being produced. In the metallurgical facilities producing aluminum, aluminum is tapped daily or every other day from electrolytic cells containing refined materials at different stages. Batches from different electrolytic cells are then mixed in the foundry to produce the target grade of product. Certain elements are known to be critical to the quality of the final product, therefore the content of these elements needs to be determined before mixing begins.

[0007] The primary aluminum production facility has electrolytic cells arranged side-by-side, each containing approximately 10 tons of liquid aluminum, beneath which lie liquid salt and a solid salt layer (cryolite layer). The depth and height of the liquid metal bath vary depending on the amount of aluminum and the age of the electrolytic cells. Due to the geometry of these electrolytic cells, sampling cannot be performed through visual contact with the metal interface.

[0008] To obtain aluminum samples from an electrolytic cell, the existing sampling process involves using a preheated, coated spoon as the sampling device. The spoon is inserted into the aluminum pool through cryolite, and after the filled spoon is withdrawn and the obtained cryolite is poured out, the remaining aluminum is poured into a copper mold. This sampling process exposes the sodium (Na) contained in the sample to air, and some of the sodium evaporates, thus being lost from the sample. After a cooling period, the sample is obtained and sent to a remote laboratory, where it is prepared into a form suitable for final analysis. These steps are time-consuming, and there is a desire to reduce the time between sampling and final analysis. Furthermore, manually handling molten aluminum with a spoon is a hazardous operation and should be avoided.

[0009] Sampling systems, including sampling guns that carry suitable sample units, are commonly used in steel casting applications. Such devices are disclosed, for example, in EP 0893681 A1. These devices are used to immerse a sample unit below the surface of the molten metal to be sampled, wherein a sample chamber positioned within the sample unit is filled. A cardboard tube may be arranged between the sampling gun and the sample body to extend the overall length of the device. The sample unit typically comprises two parts: a refractory body and a sample chamber assembly disposed within the refractory body. The sample chamber assembly includes molds defining the hollow sample chamber, which are typically a two-part clamshell arrangement or rings covered by flat plates on their upper and lower sides. The sample unit also has suitable openings through which the molten metal can enter the sample chamber. After sampling, the entire device is withdrawn from the molten metal, and after the obtained sample has solidified, the refractory body is removed from the sample chamber assembly. The remaining portions of the refractory body and sample chamber assembly are waste and must be disposed of. The conventional materials used for reusable sampling guns and sample chamber components are steel, while the refractory body typically contains sandy materials, such as resin-coated silica-based sand. While these material choices are suitable for steel production facilities, they cannot be used in aluminum foundries because the iron (Fe) and silicon (Si) contained in steel, or the sand, are undesirable in the final aluminum product. Therefore, they cannot be discarded in molten aluminum baths either.

[0010] Utilizing this technology in aluminum sampling applications is not straightforward, and for other reasons, it has not been disclosed in the prior art. The sampling environments differ; in steel facilities, the sampling location can be directly observed, while in primary aluminum electrolysis cells, this direct control is hindered. Furthermore, the cryolite layer covering the primary aluminum bath places additional demands on the sampling system, requiring the sampling device to penetrate the cryolite layer without allowing salt to seep into the sample chamber. Moreover, the materials used in existing technology systems are incompatible with the requirements of Al production facilities.

[0011] Additionally, the temperature conditions in aluminum baths vary: aluminum has a melting point of 660°C, while the bath temperature typically ranges from 940°C to 980°C; this approximately 300°C difference is known as superheat. In steel production facilities, superheat typically ranges from 30°C to 170°C, depending on the type of facility and process stage. When sampling the corresponding molten metal, the liquid sample needs to be cooled and solidified as quickly and uniformly as possible to be suitable for subsequent direct analysis. Superheat, exceeding this by several orders of magnitude, places entirely different demands on suitable samplers in terms of cooling behavior and geometry.

[0012] For the reasons mentioned above, it is desirable to provide a sample unit that can be used in a sampling system to obtain samples from aluminum, especially in primary aluminum production facilities.

[0013] The purpose of this invention is to provide such a sample unit.

[0014] Another objective is to provide a sample unit that provides samples that can be directly analyzed without further processing. For suitability for direct analysis, the sample, especially its surface, needs to be homogeneous, free from segregation and contamination. This property is specifically affected by the cooling process following sampling of the liquid sample. Furthermore, the sample chamber should be completely filled during the sampling process, which also enhances homogeneity and suitability for direct analysis.

[0015] In addition, the sample unit should be compatible with the needs and environment of the aluminum production facility; specifically, the sample unit should be suitable for taking samples from molten materials with high superheat.

[0016] On another front, the sample unit should provide samples that can be analyzed with greater accuracy, especially in terms of sodium content.

[0017] In various respects, the object of the present invention is to provide a sampling system for obtaining samples from primary aluminum.

[0018] Another objective is to provide a method for taking samples from molten aluminum using a sampling system that includes a sampling gun and a sample unit.

[0019] These objectives are achieved through the subject matter defined in the independent claims.

[0020] This invention provides a sample unit for a sampling system used to take samples from a molten aluminum bath in a primary aluminum production facility. The sample unit is configured to receive a sample of molten aluminum and includes:

[0021] -Refractory body;

[0022] - Sample chamber assembly, which is arranged within the refractory body.

[0023] The sample chamber assembly includes at least two chamber components configured to enclose the sample chamber.

[0024] The sample chamber includes a top side, a bottom side, and a lateral side, wherein the lateral side extends between the top side and the bottom side.

[0025] ○The mass of the aluminum sample within the sample chamber is less than 20% of the mass of the sample chamber assembly;

[0026] - An inflow opening that is in flow connection to the sample chamber and positioned to connect to the lateral side of the sample chamber;

[0027] - An inflow conduit, which is at least partially disposed within the inflow opening.

[0028] The inflow conduit includes an inlet end and an outlet end.

[0029] ○The outlet end is arranged to be adjacent to the sample chamber, and

[0030] ○The inflow conduit is made of metal.

[0031] Preferred embodiments are defined in the dependent claims. Preferred embodiments may be implemented individually or in any possible combination.

[0032] This invention provides a sampling unit for delivering aluminum samples that can be analyzed by spectroscopic methods without further processing. It has been surprisingly found that utilizing an inflow conduit made of metal, combined with a balance ratio of the sample volume to the mass of the sample chamber assembly, allows for the provision of a sample unit that can be used to obtain samples from molten aluminum with high superheat, particularly from molten aluminum in primary aluminum production facilities. Specifically, during sampling, the sample chamber is completely and uniformly filled, and the sample is rapidly cooled within the sampler, thereby preventing leakage of the sampled aluminum. It has been further observed that the optimized geometry and rapid cooling prevent segregation within the sample, particularly in areas on the surface of the sample to be analyzed. Avoiding segregation is crucial for the accurate analysis of elements such as Fe and Si. Furthermore, the sampling accuracy, specifically related to sodium content, is improved because the sample can be obtained directly without further processing.

[0033] This invention relates to a sample unit for taking samples from a molten aluminum bath.

[0034] As used herein, the term "molten aluminum bath" is used to describe molten aluminum in a container. An alternative term for "molten aluminum bath" known to those skilled in the art is "molten aluminum." The term "molten aluminum bath" does not exclude the presence of any solid or gaseous components, including, for example, non-molten components of the corresponding metal or solid raw materials. In primary aluminum production facilities, the molten aluminum bath may be covered with a layer of cryolite. Additionally, the aluminum bath may be covered with a crust of solid material positioned above the cryolite layer; in other words, the cryolite layer may be positioned between this crust and the molten aluminum. It should be understood that the crust layer also comprises cryolite.

[0035] Sampling units are particularly advantageous for taking samples in primary aluminum production facilities. Primary aluminum should be understood as aluminum produced through the electrolytic treatment of aluminum-containing raw materials such as alumina.

[0036] The temperature of molten aluminum varies and generally depends on the composition of the aluminum and the stage of the production process. According to a preferred embodiment, the temperature of the molten aluminum bath is in the range of 850°C to 1100°C, and more preferably in the range of 900°C to 1000°C. Given that the melting temperature of aluminum is 660°C, the superheat of the molten aluminum bath is in the range of 190°C to 440°C, and more preferably in the range of 240°C to 340°C. The sample unit of the present invention is unexpectedly suitable for obtaining samples from molten metal in such cases, even at a wide range of superheats. The superheat range requires the sampling unit to be filled at the lower end of the superheat range and to remain filled at the higher end of the range. Therefore, the inflow conduit must remain open for a sufficient period to allow for complete filling, but still support freezing of the sampled molten metal before the sampling process is completed to prevent sample leakage. Additionally, segregation within the sampled material should be suppressed so that the sample can be analyzed directly after sampling and cooling, which is not possible with samplers commonly used in steel applications.

[0037] The sample unit is configured to receive a sample of molten aluminum when immersed in a bath of molten aluminum. The sample is received within the sample chamber. It should be understood that the sample unit is a single-use item.

[0038] The sample unit includes a refractory body.

[0039] The refractory body may be cylindrical or barrel-shaped. It should be understood that the refractory body constitutes the external components of the sample unit. A suitable refractory body may have a height between 20 mm and 80 mm, preferably between 30 mm and 70 mm. Preferably, the diameter of the refractory body is in the range of 20 mm to 80 mm, preferably between 30 mm and 70 mm.

[0040] The refractory body can be a monolithic refractory body; it can also comprise multiple components. For example, the refractory body may include a substantially tubular component and a closed component that is one of the openings of a closed tube. A two-component refractory body may also include an upper component and a lower component, both of which are substantially cup-shaped and configured to engage with each other. Preferably, the upper component includes a notch configured to engage with the immersion end of a sampling gun. The entire refractory body may be molded sand, or the multiple components constituting the entire refractory body may be molded sand.

[0041] The refractory body is made of any material suitable for withstanding the sampling environment, preferably also compatible with the requirements of the aluminum production facility, specifically the primary aluminum production facility. The material of the refractory body is also referred to below as "refractory material".

[0042] Preferably, the refractory material is a sand material, such as a resin-coated sand material, like resin-coated silica. The refractory material may contain a binder material, such as phenolic resin. Preferably, the refractory material contains 1% to 9% by mass, more preferably 3% to 7% by mass of the binder material. The mass percentage of the binder material should be understood as the percentage of the binder material by mass in the total weight of the refractory material.

[0043] Preferably, the refractory body has a certain porosity to allow gases generated during sampling operations to escape easily through the porous structure. Preferably, the refractory body has a porosity of at least 20%, more preferably at least 30%. For example, the refractory body may have a porosity in the range of 20% to 50%, preferably in the range of 30% to 40%. Porosity refers to a measure of the open space within the refractory body. This porosity should be understood as the volume of open space within the refractory body divided by the total volume of the refractory body.

[0044] The exemplary sample unit may have a height between 20 mm and 80 mm, preferably between 30 mm and 70 mm. Preferably, the diameter of the sample unit is in the range of 20 mm to 80 mm, preferably between 30 mm and 70 mm.

[0045] In an advantageous embodiment, the mass of the sample unit is less than 150g, preferably less than 120g, and most preferably less than 100g. In steel applications, the commonly used sample unit weighs about 300g, therefore the sample unit according to the invention has a much smaller weight, which further enhances its usability for aluminum sampling applications.

[0046] The sample unit includes a top side and a bottom side. Preferably, the top side of the sample unit is configured to engage with the immersion tip of the sampling gun, preferably in such a way that the immersion tip of the sampling gun can be inserted into the sample unit. Preferably, the top side of the sample unit is configured to completely surround the immersion tip of the sampling gun. In a preferred embodiment, the top side includes a notch configured to interact with the immersion tip of the sampling gun. Preferably, the notch is cylindrical or truncated conical.

[0047] The sample unit includes a sample chamber assembly disposed within a refractory body. The sample chamber assembly encloses the hollow volume of the sample unit that forms a sample cavity. The sample chamber assembly includes at least two chamber components configured to enclose the sample cavity. In other words, the sample cavity should be understood as a hollow component inside the sample unit configured to receive molten aluminum.

[0048] The sample cavity includes a top side, a bottom side, and a lateral side, wherein the lateral side extends between the top side and the bottom side. The top side and the bottom side are the sides of the sample cavity that extend perpendicular to the longitudinal axis of the sample unit.

[0049] The sample chamber assembly may, for example, comprise two chamber components in the form of a half-shell or cup-shaped part and a flat cover. In an alternative embodiment, the sample chamber assembly may comprise two flat plates and a ring, wherein the two flat plates are arranged on opposite sides of the ring and close the tubular hollow volume of the ring. Preferably, the sample chamber assembly comprises two flat plates and a ring. In such cases, the lateral sides of the sample chamber assembly are limited by the inner wall of the ring, and the top and bottom sides are limited by one side of one of the respective plates. This configuration is particularly advantageous because the obtained sample is symmetrical and includes two sides that can be analyzed in subsequent analyses.

[0050] The chamber components of the sample chamber assembly are preferably formed of a material that is a good thermal and electrical conductor, and preferably of metal. The metal can be, for example, aluminum, copper, or another metal with similar thermal and electrical conductivity properties. Preferably, the components of the sample chamber assembly are made of aluminum and / or copper, and even more preferably, all chamber components are made of aluminum. By using aluminum, no additional contaminating elements are introduced into the molten aluminum during sampling, and additionally, the remainder of the sample chamber assembly can be directly discarded in the aluminum bath after the sampling process.

[0051] Preferably, at least two chamber components are detachable from each other.

[0052] In a preferred embodiment, at least one of these chamber components is configured to be inseparable from the sample. The sample should be understood as a solidified sample of molten aluminum contained within the sample chamber after the sampling process. This configuration is particularly advantageous because the chamber component can be used to position and manipulate the sample in subsequent analyses. Furthermore, the chamber component can act as a coolant during analysis, thereby preventing the sample from overheating and thus leading to more accurate results.

[0053] According to the present invention, the mass of the aluminum sample within the sample chamber volume is less than 20% of the mass of the sample chamber assembly. The mass of the sample chamber assembly refers herein to the combined mass of the chamber components. A relatively low sample mass relative to the sample chamber assembly ensures that the sample cools sufficiently rapidly to obtain a sample that meets the requirements in terms of homogeneity and filling, even for molten materials with high superheat (such as the aluminum to be sampled). Furthermore, the chamber can be filled sufficiently quickly to ensure complete filling without leaving hollow portions, which would otherwise hinder reliable subsequent analysis. It should be understood that "sample mass" refers only to the portion of the sampled aluminum within the sample chamber; specifically, the sampled metal flowing into the conduit is not considered part of the sample mass.

[0054] In a preferred embodiment, the mass of the aluminum sample within the volume of the sample chamber is less than 15% of the mass of the sample chamber assembly, or even more preferably less than 10%. For example, the mass of the aluminum sample within the volume of the sample chamber is in the range of 2% to 20% of the mass of the sample chamber assembly, more preferably in the range of 3% to 15%, or even more preferably in the range of 4% to 10%.

[0055] Preferably, the mass of the sample chamber assembly is in the range of 10g to 30g, more preferably in the range of 12g to 25g.

[0056] The mass of the sample chamber assembly preferably accounts for no more than 40% of the mass of the sample unit, and more preferably no more than 30%. For example, the mass of the sample chamber assembly may account for 10% to 40% of the total mass of the sample unit, and more preferably 20% to 30%.

[0057] Preferably, the mass of the aluminum sample within the sample chamber volume is in the range of 0.3g to 5g, more preferably in the range of 0.5g to 4g, and even more preferably in the range of 0.6g to 3.5g. The mass of the aluminum sample within the sample chamber volume should be understood as the mass of the solid within the sample chamber volume at 20°C with a density of 2.7g / cm³. Preferably, the volume of the sample chamber assembly is in the range of 100mm³ to 1900mm³, more preferably in the range of 150mm³ to 1500mm³, even more preferably in the range of 200mm³ to 800mm³, and most preferably in the range of 200mm³ to 500mm³.

[0058] Preferably, the volume of the sample cavity is less than 30% of the volume of the chamber component enclosing the sample cavity. The volume of the sample cavity herein refers to the hollow chamber enclosed by the sample chamber component. A sample cavity with a relatively low volume relative to the volume of the chamber component ensures that the sample cools sufficiently quickly to obtain a sample that meets the requirements in terms of homogeneity and fillability. In a preferred embodiment, the volume of the sample cavity is less than 25% of the volume of the sample chamber assembly, and even more preferably less than 20%.

[0059] Preferably, the volume of the chamber component is in the range of 3000 mm³ to 9000 mm³, more preferably in the range of 3500 mm³ to 8500 mm³, and even more preferably in the range of 4000 mm³ to 8000 mm³.

[0060] Preferably, the sample chamber is completely enclosed by the chamber components; in other words, the sample chamber does not come into contact with the refractory material.

[0061] Preferably, the sample chamber assembly is entirely housed within the refractory body. Therefore, the refractory body includes a top side and a bottom side of the sample unit. The top side is preferably configured to receive the sampling gun. Preferably, the bottom side of the sample unit is closed. In other words, the side initially immersed in molten aluminum during the sampling process does not include an opening.

[0062] The geometry of the sample cavity is not further restricted. Preferably, the sample cavity has a circular cross-section perpendicular to the longitudinal axis of the sample unit. The longitudinal axis should be understood as the axis connecting the top and bottom sides of the sample unit. It is also preferred that the sample cavity includes two flat surfaces opposite each other along the longitudinal axis; in other words, the top and bottom sides of the sample cavity are preferably arranged parallel to each other.

[0063] In an advantageous embodiment of the invention, the sample chamber is constructed as a cylinder, with its top and bottom sides having approximately circular cross-sections. In other words, the sample chamber is preferably disk-shaped. Cylindrical and / or disk-shaped samples are particularly advantageous because they allow for easy direct analysis without further sample preparation and include two analytical surfaces. Additionally, this cylindrical or disk shape is advantageous because it allows for high symmetry of the sample chamber and allows for a uniform inflow of the sampled molten aluminum.

[0064] However, it has been found that for aluminum samples, a certain thickness is required for suitable repeatable analysis. The sample thickness is directly related to the height of the sample cavity. The height of the sample cavity should be understood as the length of the lateral side; the diameter is the maximum diameter of the top side. It has been found that the sample sizes commonly used when analyzing steel samples (with the emphasis on the sample being as thin as possible, in the range of 2 mm or less) are unsuitable. Without being bound by theory, it has been assumed that a certain thickness is required to ensure sufficient thermal mass of the sample during commonly applied spectroscopic analyses. Preferably, the sample cavity has a height of at least 3 mm, more preferably at least 4 mm. For example, the height of the sample cavity can be in the range of 3 mm to 8 mm, more preferably in the range of 4 mm to 7 mm.

[0065] In a preferred embodiment, the components of the sample chamber assembly are pressed together and thus held together by closure members (e.g., by springs, clips, or clamps). Alternatively or additionally, fixing members, such as adhesives, are anticipated to attach the components of the sample chamber assembly to each other. In an advantageous embodiment, the sample chamber assembly is arranged within a refractory body in a manner that does not require additional closure members. In other words, the sample chamber assembly is preferably clamped within the refractory body. By using this configuration to hold the sample chamber assembly together, the components are held together by compressive forces applied by the refractory body, and the closure is not achieved using glue or adhesives. Thus, a simplified sample unit is obtained, which further reduces the amount of potentially contaminating material in contact with the molten aluminum to be sampled.

[0066] The sample unit includes an inflow opening that is in flow connection to the sample chamber. The inflow opening should be understood as a hollow space adapted to allow molten aluminum to be sampled to flow in. Therefore, the inflow opening extends through the refractory body. In other words, the refractory body includes voids through which molten aluminum can flow into the sample chamber during sampling.

[0067] The inlet opening is positioned to connect laterally to the sample chamber. In other words, the inlet opening is located in a plane of the sample chamber that is not aligned with the longitudinal axis of the sample unit. This lateral positioning of the inlet opening allows the sample unit to be immersed in molten aluminum without the cryolite layer entering the sample chamber during passage. Additionally, this lateral positioning makes the sampling unit and sampling process more robust against potential contact with the bottom of the container.

[0068] Preferably, the inflow opening is centrally located on the lateral side of the sample cavity. Therefore, the inflowing metal is uniformly distributed within the sample cavity, resulting in a symmetrical sample.

[0069] Therefore, the sample chamber assembly includes an opening that is flowably connected to the inlet opening. Thus, there is a flow connection between the inlet opening of the sample unit and the sample chamber.

[0070] Preferably, the assembled sample chamber assembly includes only one opening. This opening should be understood as a void space within the sample chamber assembly.

[0071] Preferably, the components of the sample chamber assembly are not arranged in an airtight manner; in other words, the sample chamber assembly is gas-permeable. Therefore, the gas present in the sample chamber can exit the sampling chamber as molten metal flows in, thus preventing the formation of gas inclusions in the sample. In other words, the sample chamber assembly provides ventilation for the sample chamber during the sampling process. Methods for adjusting the gas permeability of the sample chamber assembly are known to those skilled in the art. Gas permeability can be affected, for example, by the surface texture of the chamber components, specifically by roughness, or by ventilation components (such as channels anticipated in the chamber components).

[0072] In a preferred embodiment, the gas permeability of the sample unit is greater than 3 l / min, more preferably greater than 5 l / min. Gas permeability should be understood as the gas flow rate formed when the inlet conduit of the sample unit is connected to compressed air at a pressure of 1 bar. The lower the volumetric flow rate, the lower the gas permeability. It has been surprisingly shown that the sample unit may not be overly airtight to allow for proper filling of the sample chamber assembly. Sample units with gas permeability as typically used in steel applications cannot be used for aluminum sampling. In a preferred embodiment, the gas permeability of the sample unit is less than 15 l / min, more preferably less than 10 l / min. Preferably, the gas permeability is in the range of 3 l / min to 15 l / min, more preferably in the range of 4 l / min to 10 l / min. When the gas permeability is below 15 l / min, the filling of the sample chamber assembly is optimized.

[0073] The inflow opening can be protected with a suitable component to ensure that cryolite cannot enter the sample cell before it reaches the sampling location. For example, the inflow opening can be covered with a material that dissolves or burns upon exposure to molten aluminum. Suitable components could be, for example, tape or a stopper, such as paper tape.

[0074] The sample unit includes an inflow conduit at least partially disposed within an inflow opening. In other words, the inflow conduit is configured to be received by the inflow opening. It should be understood that this inflow conduit forms a flow connection into the sample chamber through the inflow opening. Therefore, the inflow conduit allows molten metal to flow from the molten aluminum bath into the sample chamber.

[0075] According to the present invention, the inflow conduit is made of metal. In existing applications, inflow conduits are typically made of quartz. Metal is considered unsuitable due to its high thermal conductivity, which would cause premature freezing of the inflow material in the conduit before filling the sample cavity. Furthermore, the metal is thought to dissolve in the inflow metal, which would lead to distortion of the available analysis. Surprisingly, contrary to these assumptions, it has been found that, when the cavity size is appropriately fitted, inflow conduits made of metal even enhance the sampling process and the quality of the obtained sample. Specifically, the metal inlet allows for a fully filled sample while having a surface suitable for direct analysis. Without being bound by theory, it can be considered that a suitably sized metal inflow conduit allows liquid metal to enter and completely fill the sample cavity, but prevents subsequent leakage of the sample metal because the liquid metal in the inflow freezes very rapidly.

[0076] Preferably, the inflow conduit is made of steel or stainless steel.

[0077] Additionally, metal is a more robust material than quartz glass, which allows for a reduction in the size of the inflow conduit, thereby further improving the inflow behavior of the sampled liquid metal. For example, the inflow conduit may have a wall thickness in the range of 0.1 mm to 0.7 mm, more preferably in the range of 0.2 mm to 0.6 mm. Furthermore, compared to commonly used quartz tubes, metal allows for a smaller outer diameter of the inflow conduit, for example, the outer diameter of the inflow conduit may be in the range of 2 mm to 9 mm, more preferably in the range of 3 mm to 7 mm, and even more preferably in the range of 3.5 mm to 5.5 mm.

[0078] The geometry of the inflow conduit can be determined by its wall thickness (W) and outer diameter (OD). C ), inner diameter (ID C ), the total cross-sectional area defined by the outer diameter (OC) C ) and the internal cross-sectional area (IC) defined by the inner diameter. C The diameter and cross-sectional area refer to the diameter and cross-sectional area perpendicular to the longitudinal axis of the inflow conduit. The inner diameter is the diameter inside the wall of the inflow conduit, which is the outer diameter minus twice the wall thickness (ID). C =OD C -2*W).

[0079] For example, the inner diameter of the inflow catheter can be in the range of 1 mm to 5 mm, more preferably in the range of 2 mm to 4.5 mm, and even more preferably in the range of 2.5 mm to 4 mm.

[0080] The inflow conduit includes an inlet end and an outlet end. The outlet end is the end arranged immediately adjacent to the sample chamber. Therefore, the inlet end is the end through which the sampled molten metal enters the inflow conduit. The outlet end may extend into or be located within the sample chamber. In other words, the inflow conduit extends at least partially through the refractory body of the sample unit. The inlet end may protrude from the refractory body, may be located flush with the outer wall of the refractory body, or may be located within the refractory body. Preferably, the inlet end protrudes from the outer wall of the refractory body.

[0081] Preferably, the mass of the Al sample within the volume encapsulated by the inflow conduit is less than 70% of the mass of the inflow conduit, even more preferably less than 60%, and most preferably less than 50%. The mass of the Al sample within the volume encapsulated by the inflow conduit should be understood as the mass of the solid within the volume surrounded by the walls of the inflow conduit at 20°C and a density of 2.7 g / cm³. It has been shown that this ratio ensures uniform filling of the sample cavity while still ensuring sufficiently rapid cooling of the sampled metal to prevent leakage of liquid metal. For example, the volume encapsulated by the inflow conduit can be in the range of 20% to 70% of the mass of the inflow conduit, preferably in the range of 30% to 60%, and even more preferably in the range of 35% to 55%.

[0082] It has been found that the volume of the sample chamber is related to the internal cross-sectional area (IC) of the inflow conduit. C The ratio between the volume of the sample chamber (given in mm³) and the internal cross-sectional area of ​​the inflow conduit (given in mm²) affects the quality of the available aluminum sample. Preferably, the ratio between the volume of the sample chamber (given in mm³) and the internal cross-sectional area of ​​the inflow conduit (given in mm²) is in the range of 25 mm to 60 mm, more preferably in the range of 30 mm to 55 mm. When the ratio is high, the sample chamber will not be filled; when the ratio is low, liquid aluminum will leak out of the sample chamber after immersion. In typical direct analysis samplers for steel applications, the ratio is at least 60 mm; for classic samplers, the ratio is in the range of 600 mm (e.g., the Samp-O-Line for steel sampling available from Heraeus Electro-Nite International NV). ® (sampler).

[0083] In a second aspect, the present invention provides a sample unit for a sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility. The sample unit is configured to receive a sample of molten aluminum and includes:

[0084] -Refractory body;

[0085] - Sample chamber assembly, which is arranged within the refractory body.

[0086] The sample chamber assembly includes at least two chamber components configured to enclose the sample chamber.

[0087] The sample chamber includes a top side, a bottom side, and a lateral side, wherein the lateral side extends between the top side and the bottom side.

[0088] ○The mass of the Al sample within the volume of the sample chamber is less than 20% of the mass of the sample chamber assembly;

[0089] - An inflow opening that is in flow connection to the sample chamber and positioned to connect to the lateral side of the sample chamber;

[0090] - An inflow conduit, which is at least partially disposed within the inflow opening.

[0091] The inflow conduit includes an inlet end and an outlet end.

[0092] ○The outlet end is arranged to be adjacent to the sample chamber, and

[0093] ○The ratio of the volume of the sample chamber to the internal cross-sectional area of ​​the inflow conduit is in the range of 25 mm to 60 mm.

[0094] All the features, advantages, and embodiments mentioned in the first sample unit according to the invention also apply to the second sampling unit of the invention.

[0095] A second aspect of the invention provides a sampling unit that delivers a sample that can be analyzed by spectroscopic methods without further processing. Surprisingly, an optimized ratio between the sample mass, sample size, and inflow conduit size has been found to allow for the provision of a sample unit that can be used to obtain samples from molten aluminum, particularly from molten aluminum with high superheat in primary aluminum production facilities. Specifically, during sampling, the sample chamber is completely and uniformly filled, and the sample is rapidly cooled within the sampler.

[0096] In another aspect, the present invention provides a sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility, the sampling system comprising a sample unit and a sampling gun according to the invention. The sampling gun has an immersion end and a gripping end and is configured to engage the sample unit.

[0097] All the features, advantages, and embodiments mentioned in the sample unit according to the invention also apply to the sampling system of the invention.

[0098] Surprisingly, it has been found that the sampling system, including the sample unit and sampling gun of the present invention, can also be applied to aluminum sampling applications in primary aluminum production facilities. The sampling system provides a combination of a sampling unit and an immersion sampling gun, which delivers a directly analyzable sample, avoiding all risks of bath contamination. The immersion sampling gun is preferably reusable and maintenance-free.

[0099] An added benefit of this sampling system is its compatibility with the environment present in aluminum production facilities.

[0100] The sampling system includes a sampling gun with an immersion end and a gripping end.

[0101] The immersion end should be understood as the end portion of the sampling gun on one side. The immersion end is configured to be immersed in molten aluminum. The immersion end terminates at the immersion tip; in other words, the end portion of the immersion end is the immersion tip. The grip end is the opposite end of the sampling gun; in other words, the sampling gun extends from the immersion end to the grip end.

[0102] The sampling gun can be formed as a straight rod, or it can be curved. Preferably, the sampling gun is curved. This configuration allows the sampling gun to have at least two parts: an immersion portion extending from the immersion end to the curved portion; and a gripping end extending from the curved portion to the gripping end. Preferably, in such cases, the bending angle is in the range of 120° to 160°.

[0103] The sampling gun can be formed as a single unit, and it may also include multiple components that are fixed to each other in a suitable manner (e.g., by threaded members, welding, press fitting, or a combination thereof). The sampling gun may include additional components (such as gripping components), which are preferably located at the gripping end of the sampling gun.

[0104] The material for the sampling gun is selected to be compatible with the environment of the aluminum production facility. For example, the sampling gun, especially the immersion parts, needs to withstand high temperatures, specifically the temperature of molten aluminum. The melting point of aluminum is 660°C; however, the temperature of the molten aluminum bath in the aluminum production facility is often even higher. This temperature resistance is particularly relevant to the immersion parts of the sampling gun. Therefore, the material of the immersion tip of the sampling gun has a melting point above 950°C.

[0105] Suitable materials for the immersion tip of the sampling gun are, for example, stainless steel and copper. In a preferred embodiment, the immersion tip of the sampling gun is made of stainless steel, specifically austenitic stainless steel (e.g., stainless steel 316L).

[0106] The sampling gun can be made of only one material, and it can also be advantageous when different parts of the sampling gun are made of different materials. For example, the immersion end can be made of stainless steel, while the grip end can be made of aluminum. Thus, the sampling gun assembly can be designed to be cost-effective and lightweight.

[0107] The immersion end of the sampling gun is preferably formed as a hollow body, for example, as a tube. The cross-section of the immersion end can be circular, or it can have various other shapes (e.g., square, triangular, polygonal). The tube can have a thickness ranging from 1 mm to 10 mm, wherein the inner diameter is between 5 mm and 35 mm, and the outer diameter is between 10 mm and 40 mm. It is anticipated that the tube has connecting members configured to connect several parts of the sampling gun to each other, for example, by means of threaded members.

[0108] The sampling gun is configured to engage a sample unit, preferably to be inserted into the sample unit. Most preferably, the immersion tip of the sampling gun is configured to be inserted into the sample unit. In other words, in use, the immersion tip of the sampling gun carries the sample unit. Specifically, the immersion tip is configured to engage the sample unit, that is, the immersion tip is configured to be inserted into the sample unit. The outer diameter and shape of the immersion tip are configured to mate with, in particular, flush with, the sampling unit. In such cases, the sample unit is configured to be engaged by the immersion tip of the sampling gun, preferably, the sample unit includes a notch configured for insertion into the immersion tip of the sampling gun.

[0109] Another aspect of the invention is a method for sampling from a molten aluminum pool in a primary aluminum production facility, the primary aluminum production facility having a sampling system including a sample unit and a sampling gun of the present invention. The sampling gun has an immersion end and a gripping end and is configured to engage the sample unit. The method includes the following sequential steps:

[0110] (a) Provide a sampling system;

[0111] (b) Immerse the sample unit and the immersion end of the sampling gun into a bath of molten aluminum;

[0112] (c) When the molten aluminum sample has filled the sample chamber, withdraw the sample unit and the immersion end of the sampling gun from the molten aluminum bath;

[0113] (d) Separate the sample from the sample unit.

[0114] All features, advantages, and embodiments mentioned in the sampling system for sampling guns and sample units according to the present invention also apply to the method of the present invention.

[0115] In step (a), the method includes providing a sampling system. Providing a sampling system should be understood as providing a sampling gun that engages a sample unit. In other words, the sampling system includes a sample unit coupled to or connected to the sampling gun.

[0116] In step (b), the method includes immersing the sample unit and the immersion tip of the sampling gun into a bath of molten aluminum. Following step (b), the sample unit and the immersion tip are positioned at a sampling location below the surface of the molten aluminum bath. During immersion, the sample unit and the immersion tip of the sampling gun move through a cryolite layer, which typically covers the molten aluminum bath.

[0117] To minimize the contact time between the immersion unit and the immersion tip of the sampling gun and the cryolite layer before sample entry, a sufficiently high immersion velocity is required. Preferably, the immersion velocity is at least 20 cm / s, more preferably at least 30 cm / s. For example, a suitable immersion velocity is in the range of 20 cm / s to 50 cm / s.

[0118] During the passage of the sample unit and the immersion end of the sampling gun through the cryolite layer, the cryolite freezes onto the introduced cold components when the materials of the sampling gun and sample unit are selected in a suitable manner. Therefore, a frozen cryolite crust accumulates at the joint between the sample unit and the immersion end of the sampling gun, as well as on the exterior of the sample unit. Surprisingly, this cryolite crust has been found to be advantageous for the method of the present invention. The cryolite crust enhances the seal at the joint and on the sample unit, allowing molten aluminum to enter the sample unit only through the inflow opening, specifically through the inflow conduit. Furthermore, when the sampling gun is withdrawn from the melt, it is protected from both the molten aluminum and ambient oxygen, which extends the life of the sampling gun and enhances its reusability.

[0119] The immersion of the sample unit and the immersion tip of the sampling gun may include more than one sub-step. For example, the method may include:

[0120] (i) Immersing the sample unit and the immersion end into a first position, in which the sample unit contacts the bottom of the molten aluminum bath, and

[0121] (ii) Pull the sample unit and immersion end back to the sampling position between the bottom of the aluminum bath and the surface of the molten aluminum bath.

[0122] This sub-step process ensures that the sample unit is positioned at the appropriate sampling location when molten aluminum enters the sample chamber.

[0123] Once the immersion unit is positioned in the molten aluminum bath, molten aluminum flows through the inlet opening into the sample chamber. The molten aluminum entering the sample chamber will build the sample. If there are components on or at the sample unit for covering the inlet opening, this filling will begin after such components have dissolved, burned, or otherwise decomposed.

[0124] In step (c), the method includes withdrawing the sample unit and the immersion end of the sampling gun from the molten aluminum bath when the molten aluminum sample has filled the sample cavity.

[0125] In step (d), the method includes separating the sample unit from the sample. Therefore, the sample is removed from the sampling system, and more specifically from the sample unit. Removal typically occurs after a cooling period during which the molten aluminum sample solidifies within the sample chamber. It should be understood that removing the sample unit involves destroying the sample unit components surrounding the sample.

[0126] The method may include additional steps. For example, the method may include the step of removing the sample unit from the sampling gun and / or the step of discarding the remainder of the sample unit in a bath of molten aluminum.

[0127] Preferably, after the sample is removed from the sample unit, it is delivered to the analytical apparatus. The sample can be analyzed directly using a suitable spectroscopic technique, such as OES or LIBS analysis.

[0128] The following schematic diagram illustrates aspects of the invention to improve understanding of the invention in conjunction with some exemplary illustrations, wherein

[0129] Figure 1 A sampling system with a sample unit and a sampling gun in use is shown.

[0130] Figure 2 Sample units at different assembly stages according to the present invention are shown.

[0131] Figure 3 The immersion end of the sampling gun with attached sample units is shown in more detail.

[0132] Figure 4 An alternative configuration of the sample chamber assembly is shown.

[0133] The accompanying drawings illustrate various embodiments and, together with the description, serve to explain the principles of the invention. Elements in the drawings are not necessarily to scale. Similar reference numerals denote corresponding similar parts.

[0134] Figure 1 A sampling system 1 in use is shown. An operator 2 holds a sampling gun 3 and manually inserts it into a container 4 containing molten aluminum 5. The aluminum bath 5 is covered with an ice crystal layer 6; a crust layer 7 covers the ice crystal layer 6. The sampling gun 3 shown includes an immersion portion 8 and a grip portion 9 with a handle 10. A sample unit 11 is arranged at the end of the immersion portion 8 (i.e., the immersion end 13).

[0135] For the sampling process, operator 2 introduces sampling gun 3 into container 4. During this process, operator 2 has no visual contact with the inside of the container. The immersion end 13 of sampling unit 11 is immersed in aluminum bath 5 through the crust layer 7 and cryolite layer 6. Cryolite typically has a superheat of only 10°C, meaning its temperature exceeds the melting temperature of the material by only 10°C. Therefore, during the passage through cryolite layer 6, the cryolite freezes onto the cold component of sampling system 1, specifically, onto the connector between immersion end 13 and sample unit 11. This frozen layer protects sampling gun 3, specifically the immersion end 13 of the sampling gun, from dissolving in the cryolite and also seals the connector between immersion end 13 and sample unit 11. After the immersion of sample unit 11, the sample chamber 12 ( Figure 1 (Not visible in the container) will be filled with molten aluminum. After the immersion sampling gun 3 and sample unit 11 are withdrawn from container 4, sample unit 11 may easily break, thereby releasing the sample.

[0136] After cooling, the cryolite frozen onto the immersion sampling gun becomes brittle and can be removed from the gun, which can then be reused. The material of the sampling gun, particularly the immersion tip 13, needs to be selected to meet the requirements of the container and the corrosive properties of the cryolite material. Samples obtained in the sample unit 11 of the present invention can be used directly for analysis, or even analyzed directly at the sampling site. All waste materials from the sample unit are selected to contain only non-contaminating materials, and therefore can be disposed of in the container with the molten aluminum without generating waste or introducing undesirable additives into the molten metal.

[0137] Figure 2 The sample unit 11 at different assembly stages according to the present invention is shown. To assemble the sample unit 11, the chamber components (27, 28, 29) are first inserted into the recesses of the first bottom component 21 of the refractory body. Subsequently, the refractory body is closed with the second top component 22. This allows for a very simple assembly. Figure 2 Figure A shows the bottom component of sample unit 11, including the bottom component of refractory body 21. It is foreseeable that the bottom component of the refractory body has a recess 23 as an inlet for inflow conduit 24, which forms part of inflow opening 25. Two components of the three-part sample chamber assembly 26 (bottom disc plate 27 and a central ring 28 that holds the inflow conduit 24) and sample chamber 30 are visible. The inflow conduit 24 is centrally positioned within the ring 28. After the sample chamber 30 is covered with a second disc plate 29, sample unit 11 is sealed with a second sand body 22. The upper sand body 22 includes a notch 38 configured to engage with an immersion sampling gun. An adhesive 31 is also provided to provide adhesion and sealing between the two components of the refractory body 20. Figure 2 C shows an external view of the fully assembled sample unit 11, with the inflow conduit 24 partially protruding. The opening of the inflow conduit can then be covered, for example, with paper tape (not shown) to prevent cryolite from entering the sample chamber.

[0138] Figure 3 The immersion end 13 of the sampling gun 3 and the sample unit 11 (composed of...) are shown in more detail. Figure 1 (The dashed box indicates this). Figure 3 Figure A shows an external view of the immersion end 13 of a sampling gun 3 on which a sample unit 11 is mounted. The immersion end 13 includes a component 35 with a smaller diameter and a component with a larger diameter, forming a collar 36 in such a way that the collar 36 is flush with the sample unit 11 on its outer circumference. Figure 3 In view A, only the outer surface of the refractory body 20 of sample unit 11 is visible. The laterally arranged inflow opening 25 leads to the sample chamber assembly 26 arranged inside the refractory body 20 (in...). Figure 3 (Not visible in view A). Refractory materials are porous fire-resistant materials, such as silica-based sand.

[0139] exist Figure 3 In B, it is shown that along... Figure 3 A schematic cross-section of line X in A, showing a detailed view. Sample unit 11 is engaged by the immersion end 13 of the sampling gun. The sampling gun includes a main tubular body 34 and an immersion end designed with a collar 36 and a protrusion 37.

[0140] The sample unit 11 has a tapered inlet 38 on its top side, into which the tip of the immersion end 13 is inserted. When the refractory sand body 20 is pressed against the tip of the immersion end against the collar 36, such that the refractory body 20 surrounds the outside of the tip of the immersion end, the protrusions 37 extending from the immersion end scrape the inner surface of the body, thus holding the sample unit 11 in place by these protrusions 37.

[0141] The sample chamber assembly 26 is arranged approximately axially symmetrically within the refractory body 20. This sample chamber assembly is essentially constructed in a cylindrical shape. According to... Figure 2 The components shown in the figure, the sample chamber assembly 26 includes three parts (27, 28, 29) that surround the cylindrical sample chamber 30.

[0142] It is anticipated that an opening is provided on one side of the sample chamber assembly 26, which is arranged to flow in communication with the inflow opening 25 of the surrounding refractory body 20 via the inflow conduit 24.

[0143] The sample chamber assembly 26 is completely outside and separate from the immersion end 13 of the sampling gun, facilitating sample release. The sample can be released from the sample unit 11 simply by breaking the refractory body 20. After the sample is released from the refractory body 20, the plates (27, 29) of the chamber assembly are also removed, and the sample remains in the annular component of the assembly 28 to which the inflow conduit 24 is attached. Therefore, the sample can be easily manipulated during the subsequent analytical procedures.

[0144] Figure 4 Two alternative configurations of the sample chamber assembly 26 are shown, each of which includes only two chamber components. Figure 4 Component A includes a cup-shaped bottom part 40 and a disc-shaped plate 41 located at the top, which encloses the chamber assembly 26. Dimensional parameters used to describe the chamber assembly are also shown. The volume of the sample chamber 30 is determined by its height (H). S ) and its width (W) S (Identified.) The inflow conduit 24 passes through the outer diameter OD. C and inner diameter ID C To characterize. Figure 4 The components of B consist of two half-shells (42a, 42b) that symmetrically enclose the sample cavity 30.

[0145] It should be understood that all described implementation schemes can be combined without contradicting each other.

[0146] Example:

[0147] The filling behavior and sample quality of different sample chamber configurations and inlet tubes were evaluated. For all embodiments, an aluminum sample chamber was positioned within a two-part sand body comprising a central ring with an opening for the inlet tube and two discs of the same outer diameter located at the bottom and top of the ring, through which the inlet tube enters the sample chamber. The chamber components enclose the disc-shaped chamber. The barrel-shaped sand body has an external height of 45 mm and a maximum diameter of 41 mm.

[0148] The obtained sample unit was positioned on the sampling gun to obtain a molten aluminum sample. Subsequently, the sand body was crushed and the disk encapsulating the sample chamber was removed to obtain the final sample, which was encapsulated by the ring of the sample chamber.

[0149] The samples were visually inspected to assess their filling behavior and sample surface quality.

[0150]

[0151] +- Fully filled / Sufficient sample mass

[0152] --Incomplete filling / Insufficient sample quality

[0153] Only by utilizing embodiments #1 and #2 of the present invention can a complete sample with good surface quality be obtained.

[0154] Figure Labels

[0155] 1 Sampling System

[0156] 2 operators

[0157] 3 sampling guns

[0158] 4 containers

[0159] 5 aluminum bath

[0160] 6 layers of ice crystal

[0161] 7. Crust

[0162] 8. Immersion part of the sampling gun

[0163] 9. Handle of the sampling gun

[0164] 10 handles

[0165] 11 sample units

[0166] 12 sample chambers

[0167] 13 Immersion end

[0168] 20 refractory body

[0169] 21. Bottom components of the refractory body

[0170] 22 Top components of refractory body

[0171] 23. Inlet of the inlet catheter

[0172] 24 Inflow catheter

[0173] 25 Inflow Opening

[0174] 26 Sample Chamber Components

[0175] 27. Bottom tray of the sample chamber assembly

[0176] 28. Central component of the sample chamber assembly

[0177] 29. Top tray of the sample chamber assembly

[0178] 30 sample chambers

[0179] 31 Adhesive

[0180] 34 Sampler tube

[0181] 35 Small diameter components immersed at the end

[0182] 36 rings

[0183] 37 protrusions

[0184] 38 Conical Sampling Gun Inlet

[0185] 39. Opening of the sample chamber assembly

[0186] Bottom component of 40 sample chamber assembly

[0187] 41. Disc-shaped plate of the sample chamber assembly

[0188] 42 Sample chamber assembly half shell

Claims

1. A sample unit of a sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility. The sample unit is configured to receive a sample of molten aluminum and includes: -Refractory body; - Sample chamber assembly, the sample chamber assembly being disposed within the refractory body. ○ The sample chamber assembly includes at least two chamber components configured to enclose the sample chamber. ○ The sample chamber includes a top side, a bottom side, and a lateral side, wherein the lateral side extends between the top side and the bottom side, and ○ The mass of the aluminum sample within the sample chamber volume is less than 20% of the mass of the sample chamber assembly; - Inflow opening, which is flow-connected to the sample chamber and positioned to connect to the lateral side of the sample chamber; - An inflow conduit, which is at least partially disposed within the inflow opening. ○ The inflow conduit includes an inlet end and an outlet end. ○ The outlet end is the end arranged immediately adjacent to the sample chamber, and ○ The inflow conduit is made of metal.

2. The sample unit according to claim 1, wherein the inflow conduit is made of steel or stainless steel.

3. The sample unit according to claim 1 or 2, wherein the mass of the aluminum sample within the volume of the sample chamber is in the range of 2% to 20% of the mass of the sample chamber assembly.

4. The sample unit according to any one of the preceding claims, wherein the mass of the aluminum sample within the volume of the sample cavity is in the range of 0.3g to 5g.

5. The sample unit according to any one of the preceding claims, wherein the sample chamber assembly is gas-permeable.

6. The sample unit according to any one of the preceding claims, wherein the refractory body has a porosity of at least 20%.

7. The sample unit according to any one of the preceding claims, wherein the sample chamber is completely enclosed by the chamber component.

8. The sample unit according to any one of the preceding claims, wherein the gas permeability of the sample unit is greater than 3 l / min.

9. The sample unit according to any one of the preceding claims, wherein the sample cavity is configured as a cylinder, and the top and bottom sides of the sample cavity have approximately circular cross-sections.

10. The sample unit according to any one of the preceding claims, wherein the material of the sample chamber assembly is copper or aluminum.

11. The sample unit according to any one of the preceding claims, wherein the at least two chamber components are detachable from each other.

12. The sample unit according to any one of the preceding claims, wherein at least one of the chamber components is configured to be inseparable from the sample.

13. A sample unit of a sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility. The sample unit is configured to receive a sample of molten aluminum and includes: -Refractory body; - Sample chamber assembly, the sample chamber assembly being disposed within the refractory body. ○ The sample chamber assembly includes at least two chamber components configured to enclose the sample chamber. ○ The sample chamber includes a top side, a bottom side, and a lateral side, wherein the lateral side extends between the top side and the bottom side, and ○ The mass of the aluminum sample within the sample chamber volume is less than 20% of the mass of the sample chamber assembly; - Inflow opening, which is flow-connected to the sample chamber and positioned to connect to the lateral side of the sample chamber; - An inflow conduit, which is at least partially disposed within the inflow opening. ○ The inflow conduit includes an inlet end and an outlet end. ○ The outlet end is the end arranged immediately adjacent to the sample chamber, and ○ The ratio of the volume of the sample chamber to the internal cross-sectional area of ​​the inflow conduit is in the range of 25 mm to 60 mm.

14. A sampling system for taking samples from a molten aluminum bath in a primary aluminum production facility, the sampling system comprising: - Sample unit according to any one of claims 1 to 12 or 13, - A sampling gun having an immersion end and a gripping end, wherein the sampling gun is configured to engage the sample unit.

15. A method for taking a sample from a molten aluminum bath in a primary aluminum production facility, the method comprising the following sequential steps: (a) Providing a sampling system comprising a sampling gun and a sample unit according to any one of claims 1 to 12 or 13. The sampling gun has an immersion end and a gripping end, and is configured to engage the sample unit; (b) Immerse the sample unit and the immersion end of the sampling gun into the molten aluminum bath; (c) When the molten aluminum sample has filled the sample cavity, the sample unit and the immersion end of the sampling gun are withdrawn from the molten aluminum bath; (d) Separate the sample from the sample unit.

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