Heat-resistant lance assembly and heat-resistant lance tube

Abstract

Various embodiments of refractory lance assemblies and composite refractory lances are described. In one embodiment, a refractory lance assembly is provided that includes a submerged tube having a submersible end in the melt and an extension tube connected to an opposite end thereof to form a longitudinally extending composite tube defining an optical path therein, the longitudinally extending composite tube being capable of injecting an inert gas during use to form and probe a submerged melt surface. The assembly further includes a shroud that longitudinally houses the composite tube and into which an inert gas can be injected to reduce fluid contamination of the composite tube and the submerged melt surface.

Description

[Technical field]

[0001] The present disclosure relates to pyrometallurgical processes and monitoring, and in particular to refractory lance assemblies and refractory lance tubes. [Background technology]

[0002] In various pyrometallurgical processes, timely determination of the chemical composition of the molten material is essential to achieve efficient process control. Generally, quantitative determination of specific constituents is required to inform adjustment of operating parameters and thus to obtain products of desired composition or properties. However, the harsh conditions inherent in pyrometallurgical processes, including high temperatures, make direct compositional measurements of the molten material difficult. This is especially true in the iron and steel industry, where molten material flows at temperatures above 1500°C are common.

[0003] Several methods are available for the compositional measurement of high melting point molten materials. For example, the simplest method involves obtaining a sample from a bath of molten material, cooling or quenching it, laboriously preparing the sample for analysis, and finally analyzing the composition using offline laboratory equipment. One drawback of this method is the inevitable time delay (ranging from minutes to hours) between obtaining the sample and determining the composition. Furthermore, the offline nature of the method means that real-time and / or continuous compositional measurement of the molten material is not possible, requiring the operator to select discrete time points for the measurement depending on the specific application.

[0004] For high melting point molten materials, various indirect sensing means can be utilized to obtain more continuous composition measurements. Indirect sensing involves measuring properties of the molten material that are less complicated to obtain than direct composition measurements, such as temperature, oxygen activity, and off-gas composition, and utilizing known material relationships to relate such indirectly measured properties back to the composition of the molten material. Indirect methods are limited in terms of accuracy. For example, certain indirect methods, such as measuring temperature, are only relevant for measuring selected elements or compounds that are significantly affected by temperature. Furthermore, reliance on certain assumptions (such as the assumption of thermodynamic equilibrium) can introduce errors into the calculated composition (e.g., by ignoring the effects of reaction kinetics).

[0005] Laser-induced breakdown spectroscopy (LIBS) can therefore be used to provide direct, real-time, and continuous compositional measurements of molten materials. In a typical configuration, LIBS involves repeatedly emitting short, high-energy laser pulses from a remote location towards a target spot of molten material to ablate or vaporize material to form a plasma. The plasma emits electromagnetic radiation that is analyzed by a spectrometer, and as with other spectroscopic techniques, this analysis is correlated to elemental composition and / or concentration through analysis of the plasma's spectral features. One drawback of systems that use traditional LIBS to perform compositional measurements of molten materials is that the melt surface is often metallurgically different from the bulk melt and therefore may not provide an adequate, representative measurement of the bulk melt. This may be due to a variety of reasons, including reactions occurring between the melt's surface material and the atmosphere (e.g., oxidation), or residual slag, raw materials, or other impurities floating on the surface of the melt.

[0006] To combat this, some LIBS approaches involve inserting a lance, typically filled with an inert gas, into the melt and directing a laser pulse through the lance. When the lance is inserted into the melt, there is usually enough pressure in the lance to balance the hydrostatic pressure of the molten material at the measurement point while keeping the melt surface relatively static. Composition measurements at a relatively static surface simplify LIBS measurements but create other metallurgical problems. Primarily, molten materials (especially metals) are generally heterogeneous and consist of a variety of prills, inclusions, etc. Therefore, measurements at a stagnant surface may not be representative of the bulk melt, especially when the molten bath is stagnant.

[0007] To this end, US Patent No. 6,909,505 by Lucas et al., published June 21, 2005, discloses a "bubbling technique" that involves inserting the tip of a lance into the molten material (below the slag), flowing gas through the lance to create bubbles in the molten material at the tip, and then measuring the composition of the inner surface of the bubble by LIBS. Thus, the bubbling technique provides a way to obtain real-time, in-line compositional measurements of the molten material. Although the bubbling technique comes with its own challenges, such as random fluctuations from the bubbles causing fluctuations in the plasma emission light received by the detector, it is considered superior from a metallurgical point of view because the measurement surface is constantly renewed with new material from the bulk melt. This bubbling technique is effective for molten aluminum, zinc, lead, and other low melting point metals that typically have melting temperatures up to 1000°C.

[0008] Existing lances for real-time, continuous LIBS composition measurements, such as those utilized in the bubbling technique, suffer from significant drawbacks at high temperatures, including low mechanical strength, thermal shock during insertion into the melt, corrosion by molten material and / or slag, as well as chemical reactivity in the molten state. For example, such lances are typically fabricated from porous ceramics, such as alumina, which exhibit corrosion and thermal shock resistance. However, because the pore sizes of porous ceramics can vary between 6 nm and 500 μm, these lances are generally permeable, which is problematic, especially when obtaining sensitive LIBS measurements. Other known lances are fabricated from fused silica or Sialon II, both of which have poor corrosion and thermal shock resistance at high temperatures. Still other known lances require additional cooling mechanisms to withstand high temperatures, which is undesirable as it poses a safety hazard.

[0009] This background information is provided to identify information believed by applicant to be relevant, and is not necessarily intended, nor should it be construed, as an admission that any of the preceding information constitutes prior art or forms part of the common general knowledge in the relevant art. Summary of the Invention

[0010] The following presents a simplified summary of the general inventive concepts described herein in order to provide a basic understanding of some aspects of the disclosure. This summary is not intended to be an extensive overview of the disclosure. It is not intended to limit key elements or critical elements of the embodiments of the disclosure or to delineate their scope beyond what is expressly or implicitly set forth in the following description and claims.

[0011] There is a need for a heat resistant lance assembly and a heat resistant lance tube that overcomes some of the shortcomings of the known art, or at least provides a useful alternative thereto. Accordingly, some aspects of the present disclosure provide examples of heat resistant lance assemblies and heat resistant lance tubes.

[0012] According to one aspect, a refractory lance assembly is provided for use with an optical detection system to optically probe a melt. The refractory lance assembly comprises a submersible end of a dip tube submersible in the melt and an extension tube connected to an opposite end thereof to form a longitudinally extending composite tube defining an optical path for optically aligning with an optical detection system. The longitudinally extending composite tube is injectable with an inert gas during use to form a molten surface submerged in the melt via the submerged end, thereby optically probing the immersed molten surface exposed to the inert gas via the optical path. The refractory lance assembly also comprises a shroud that longitudinally houses the longitudinally extending composite tube to define a containment volume therebetween. The submerged end extends longitudinally therefrom for immersion in the melt, while a connection of the extension tube with the opposite end of the submersible tube is housed within the containment volume. The containment volume is injectable with an inert gas to reduce fluid contamination of the longitudinally extending composite tube and the immersed melt surface through the connections.

[0013] In one embodiment, the shroud coaxially houses a longitudinally extending composite tube.

[0014] In one embodiment, the shroud extends longitudinally beyond the connection toward the submerged end at least 1 inch.

[0015] In one embodiment, the shroud extends longitudinally beyond the connection toward the submerged end at least 2 inches.

[0016] In one embodiment, the dip tube and the extension tube have similar coefficients of thermal expansion.

[0017] In one embodiment, the dip tube has corrosion and thermal shock resistance that maintains structural integrity at temperatures of at least 1500° C., while the extension tube is defined by relatively lower corrosion and thermal shock resistance.

[0018] In one embodiment, the opposite end of the dip tube is received snugly within the connecting end of the extension tube, or vice versa.

[0019] In one embodiment, the dip tube comprises a non-porous ceramic cylinder.

[0020] In one embodiment, the non-porous ceramic cylinder is made of one of boron nitride, boron nitride containing at least 40% zirconium dioxide (zirconia), or zirconia silicate boron nitride (ZSBN), which contains about 45% zirconia in a matrix of boron nitride and borosilicate glass.

[0021] In one embodiment, at least the submerged end of the dip tube comprises a ceramic cylinder coated with an insulating non-porous ceramic layer.

[0022] In one embodiment, the ceramic cylinder comprises aluminum oxide (alumina).

[0023] In one embodiment, the insulating non-porous ceramic layer is made of one of boron nitride, boron nitride containing at least 40% zirconia, or ZSBN containing about 45% zirconia in a matrix of boron nitride and borosilicate glass.

[0024] In one embodiment, the extension tube comprises a metal cylinder made of any one or more of molybdenum, chromium, iridium, niobium, osmium, tungsten, tantalum, or alloys thereof.

[0025] In one embodiment, the extension tube comprises a non-porous ceramic cylinder made of either Sialon or Sialon II or both.

[0026] In one embodiment, the longitudinally extending composite tube further comprises a coupler at the connection between the dip tube and the extension tube, the coupler being fabricated from either or both of borosilicate or calcium borate.

[0027] In one embodiment, the longitudinally extending composite tube further comprises a coupler connecting the dip tube and the extension tube, the coupler comprising one or more ferrules for receiving the ends of the dip tube and the extension tube, the one or more ferrules forming an insulating sheath over the connection.

[0028] In one embodiment, the extension tube is reusable for two or more thermal cycles, while the dip tube is replaceable with one or more alternative dip tubes.

[0029] In one embodiment, an inert gas within the containment volume is pressurized and discharged toward the melt to reduce oxidation of the melt surface.

[0030] In one embodiment, the inert gas comprises argon gas.

[0031] In one embodiment, the optical sensing system comprises a Laser Induced Breakdown Spectroscopy (LIBS) system, the optical measurements include LIBS composition measurements, and the optical path terminates in an optical window optically aligned with the LIBS system.

[0032] In one embodiment, the melt comprises at least partially molten iron, steel, nickel, copper, platinum, or alloys thereof.

[0033] According to another aspect, a heat resistant lance tube for optically probing a melt is provided, the heat resistant lance tube comprising: a dip tube having a submersible end submersible in the melt; and an extension tube connected to an opposite end thereof to form a longitudinally extending composite tube and defining an optical path therein; the dip tube being at least partially fabricated from a non-porous ceramic and being substantially resistant to corrosion and thermal shock at temperatures of at least 1500°C.

[0034] In one embodiment, the dip tube is removably connected to the extension tube to allow for replacement with at least one alternative dip tube.

[0035] In one embodiment, the non-porous ceramic contains one or more of boron nitride, boron nitride with at least 40% zirconium dioxide (zirconia), or zirconia silicate boron nitride (ZSBN), which contains about 45% zirconia in a matrix of boron nitride and borosilicate glass.

[0036] In one embodiment, the extension tube is made of metal.

[0037] In one embodiment, the metal comprises any one or more of molybdenum, chromium, iridium, niobium, osmium, tungsten, tantalum, or alloys thereof.

[0038] In one embodiment, the longitudinally extending composite tube further comprises a coupler between the dip tube and the extension tube, the coupler being fabricated from either or both of borosilicate or calcium borate.

[0039] In one embodiment, the dip tube comprises an aluminum oxide (alumina) tube with the dip end at least partially coated with a non-porous ceramic.

[0040] In one embodiment, the melt comprises at least partially molten iron, steel, nickel, copper, platinum, or alloys thereof.

[0041] Other aspects, features and / or advantages will become more apparent on reading the following non-limiting description of particular embodiments, given by way of example only with reference to the accompanying drawings, in which:

[0042] Some embodiments of the present disclosure are provided, by way of example only, and with reference to the accompanying drawings.

[0043] Elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to facilitate understanding of the various presently disclosed embodiments. Also, common but well-understood elements that are useful or necessary in commercially feasible embodiments are often not depicted to facilitate easier viewing of the various presently disclosed embodiments. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a schematic diagram of a refractory lance assembly in one embodiment, in which a sleeve or shroud surrounding a composite tube is open at one end. [Diagram 2] FIG. 2 is a side view of a refractory lance assembly according to another embodiment, in which a sleeve or shroud surrounding a composite tube is closed at one end. [Diagram 3] FIG. 3 is a longitudinal cross-sectional view of the refractory lance assembly shown in FIG. 2 along section AA, illustrating the connection between the first tube and the second tube. [Figure 4] FIG. 4 is a cross-sectional view of the heat resistant lance assembly shown in FIGS. 2 and 3 taken along section DD shown in FIG. [Diagram 5] FIG. 5 is an enlarged view of the heat resistant lance assembly shown in FIGS. 2-4, detailing sections E and F shown in FIG. 3 and showing that the length of the second tube is variable. [Figure 6] 6 is a bottom perspective view and a top perspective view of the heat resistant lance assembly shown in FIGS. 2-5, showing a composite tube with a connection housed by a sleeve or shroud. [Figure 7] FIG. 7 is a graph of the calibration curve obtained for a given melt sample on the first day of the experiment, with measurements taken using conventional laboratory techniques (x-axis) and LIBS using a refractory lance assembly (y-axis), showing that comparable results were obtained in alternative embodiments. [Figure 8]FIG. 8 is a graph of the calibration curve obtained for the same given melt sample of FIG. 7 on day 2, again performed using conventional laboratory techniques (x-axis) and LIBS using the refractory lance assembly (y-axis), showing that similar results were obtained with changes to the specific experimental setup. [Figure 9] FIG. 9 is a graph of compositional measurements, specifically component concentrations, obtained for a given molten sample using conventional laboratory techniques (x-axis) and LIBS using a refractory lance assembly (y-axis), showing that in a further embodiment, comparable results were obtained in separate experiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Various implementations and aspects of the present specification are described with reference to the details set forth below. The following description and drawings are illustrative of the present specification and should not be construed as limiting the present specification. Numerous specific details are described to provide a thorough understanding of various implementations of the present specification. However, in some cases, well-known or conventional details are not described in order to provide a concise description of the implementations of the present specification.

[0046] Various devices, apparatus, systems, and processes are described below to provide example implementations of the present disclosure. The implementations described below are not limiting of the claimed implementations, which may include processes or apparatuses different from those described below. The claimed embodiments are not limited to an apparatus or process having all of the features of any one apparatus or process described below, or to features common to some or all of the apparatus or processes described below. An apparatus or process described below may not be an implementation of the claimed subject matter.

[0047] Furthermore, numerous specific details are described to provide a thorough understanding of the implementations described herein. However, one of ordinary skill in the art will appreciate that the implementations described herein may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the implementations described herein. This may include, for example, optical detection systems such as conventional LIBS systems.

[0048] As used herein, an element may be described as being "configured to" perform one or more functions or as being "configured for" performing such functions. Generally, an element that is configured to perform a function or configured to perform a function is enabled to perform that function, suitable to perform that function, adapted to perform that function, operable to perform that function, constructed to perform that function, or otherwise capable of performing that function.

[0049] For purposes of this specification, it is understood that the terms "at least one of X, Y, and Z" and "one or more of X, Y, and Z" may be interpreted as X only, Y only, Z only, or any combination of two or more of X, Y, and Z (e.g., XYZ, XY, YZ, ZZ, etc.). Similar logic can be applied to more than one item when the words "at least one..." and "one or more..." appear.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0051] Throughout the specification and claims, the following terms have the meanings expressly associated therewith, unless the context clearly dictates otherwise. As used herein, the phrases "in one embodiment" or "in at least one of various embodiments" may refer to the same embodiment, but do not necessarily refer to the same embodiment. Furthermore, as used herein, the phrases "in another embodiment" or "in some embodiments" may refer to different embodiments, but do not necessarily refer to different embodiments. Thus, as described below, various embodiments can be readily combined without departing from the scope or spirit of the invention disclosed herein.

[0052] Additionally, as used herein, the term "or" means an inclusive "or" and is equivalent to the term "and / or" unless the context clearly dictates otherwise. The term "based on" is not exclusive and acknowledges that it may be based on additional unlisted elements unless the context clearly dictates otherwise. Additionally, throughout this specification and claims, the meanings of "a," "an," and "the" include plural references unless the context clearly dictates otherwise. "In" includes "in" and "on."

[0053] The term "comprising" as used herein will be understood to mean that the list below is not exhaustive and may or may not include any other additional suitable items, e.g., one or more further features, components, elements and / or steps.

[0054] In some explanations, the term "lance" may be understood to mean a (composite) tube that can be inserted into the melt, while in other explanations, the term may be understood to mean a (composite) tube and its sleeve or shroud, if the context indicates. Depending on the context, the term "lance" may have either or both of the above interpretations.

[0055] The term "melt" is used herein to refer to any molten material, including, but not limited to, molten metal, and includes both melts undergoing pyrometallurgical processes and sample melts taken for testing purposes. Additionally, "melt" should be understood to include impurities, prills, contents (both intrinsic and extrinsic), slag, etc., although "melt" may also include high purity melts.

[0056] To utilize known LIBS composition measurement techniques with high melting point molten materials such as iron and steel, refractory lance assemblies and refractory lance tubes that meet certain implementation criteria are proposed herein according to different embodiments. It should be understood that the implementation criteria may vary based on, for example, operating conditions or melt type, to name a few, so that several different embodiments may meet one or more different implementation criteria. Thus, these implementation criteria are provided herein as non-limiting examples of implementation criteria and may vary based on the use case of the refractory lance tube and / or assembly.

[0057] For example, a lance may need to withstand high temperatures. The melting temperature of pure iron is 1537 °C. However, in practice, temperatures of 1650 °C or more are often encountered during melting of iron due to the difficulty of controlling the temperature in furnaces. At such high temperatures, mechanical strength as well as resistance to thermal shock may be the next requirement for the lance. If the lance is damaged, cracked, or leaky, air or gas (such as oxygen or nitrogen) may enter the lance (particularly here the tube through which the optical measurements are taken), which may alter the composition measurements of the highly sensitive LIBS system and potentially affect the resulting spectral readings. For the same reason, the lance may need to be resistant to corrosion by molten material (usually metal) and / or molten slag. Corrosion resistance may also be useful or essential for other reasons, such as to extend the life of the lance. In this context, "corrosion" shall be interpreted broadly to include any one or more of the following processes: corrosion, dissolution, erosion, chemical reactivity, or processes that may damage or destroy the lance. Corrosion further includes the generation of gases resulting from the chemical reactivity of one or more materials of the lance in certain environments (due to the oxidation of other materials). Corrosion resistance allows the lance to be reused repeatedly, reducing the costs associated with a LIBS system.

[0058] The corrosion resistance requirement may be further complicated by the fact that lance materials that are resistant to certain molten metals are typically not sufficiently resistant to molten slag. For example, molten steel is highly corrosive, but materials that are resistant to molten steel (i.e., acidic materials) are typically not very resistant to molten slag (basic materials). Thus, in some embodiments, a suitable material may be required that is resistant to corrosion in both molten materials and slag. Such corrosion resistance is particularly relevant for the immersible portions of the lance, but may also be relevant to sleeves or shrouds that are placed in the furnace and exposed to similar conditions as the lance.

[0059] Further related to the requirement of corrosion resistance is the potential requirement for the lance to be chemically inert, or at least stable, at such high temperatures.

[0060] A further limitation to the use of known LIBS composition measurement techniques with high melting point molten materials is that active cooling systems may not be generally accepted or considered undesirable in the art or science due to safety concerns arising therefrom. Thus, a lance that can be utilized for high melting point metals without the use of a cooling system is desirable, or at least such a lance may provide a useful alternative to systems that require cooling.

[0061] As described herein, the embodiments provide different examples of refractory lance assemblies and refractory lance tubes that can be utilized in conjunction with optical sensing systems, such as LIBS, to obtain relatively accurate composition measurements from metals having high melting temperatures. Indeed, some of these embodiments may overcome or at least ameliorate some of the shortcomings of conventional systems by achieving one or more of the implementation criteria discussed above.

[0062] 1, a refractory lance assembly, generally referred to using the numeral 10, will be described in accordance with one exemplary embodiment. The refractory lance assembly 10 can be used in conjunction with an optical sensing system (see "LIBS", not shown in detail) to optically probe the melt 50 and, in particular, to obtain optical composition measurements from the melt 50. The refractory lance assembly 10 generally comprises a composite tube 12 defining an optical path (shown in dashed lines) therethrough. The composite tube 12 comprises a submerged tube 14 (or first tube) having a first end (submerged end) 14.1 that is submersible or insertable into the melt 50 and a second (opposite) end 14.2 to which an extension tube 16 (or second tube) is connected to longitudinally extend its length. The submerged tube 14 and extension tube 16 thus form the composite tube 12, which is referred to interchangeably herein as a longitudinally extending composite tube.

[0063] As shown, the optical path defined by the compound tube 12 is for optical alignment with an optical sensing system ("LIBS"). The compound tube 12 is further capable of injecting a pressurized inert fluid, in particular an inert gas in this embodiment, during use to form a melt surface 52 immersed in the melt 50 via a first or immersion end 14.1 and optically probe said immersed melt surface exposed to said inert gas via an optical path. The optical path and the injected gas path are described in more detail below.

[0064] The heat-resistant lance assembly 10 further includes a shroud 18 (or sleeve) that houses (i.e., surrounds) the junction or connection between the first submerged tube 14 and the extension tube 16 at a spaced apart location and defines a containment volume 20 (or gap) between the composite tube 12 and the shroud 18. In this regard, the junction or connection housed by the shroud 18 and the containment volume may refer to the junction between the tubes 14, 16 or to one or more components that form the connection between the tubes 14, 16. In this embodiment, the shroud 18 longitudinally houses (at least a portion of) the composite tube 12, with the submerged end 14.1 extending longitudinally therefrom for immersion in the melt 50. During use, the containment volume 20 is capable of injecting or receiving pressurized inert fluid therein, specifically an inert gas (e.g., argon gas), to mitigate fluid contamination of the composite tube 12 and the submerged melt surface 52 via the connection. For example, inert gas can enter the optical path from the containment volume 20 if a leak occurs within the composite tube 12 (e.g., at a connection along the length of one of the tubes 14, 16), thereby preventing the leak or mitigating potential external fluid contamination of the optical path.

[0065] As noted above, the shroud 18 longitudinally houses the composite tube 12. In particular, as shown in FIG. 1, the shroud 18 coaxially surrounds the composite tube 12 and extends from one end of the composite tube 12 along the length of the extension tube 16 across the junction or connection. In particular, the shroud 18 in this embodiment extends at least an inch or two (or 2-5 cm) beyond the junction or connection and covers the second end 14.2 of the dip tube 14. The figures may not be drawn to scale, so the proportions of the length of the shroud 18 to the composite tube 12 are not intended to be exact.

[0066] In this embodiment, the heat resistant lance assembly 10 includes a connection 22 disposed at the junction between the dip tube 14 and the extension tube 16. The shroud 18 thus covers the connection 22 such that if a leak occurs at the connection 22, the inert gas from the containment volume 20 can still enter the optical path.

[0067] In this embodiment, the dip tube 14 and the extension tube 16 comprise tubes of different lengths, with the dip tube 14 being shorter than the extension tube 16. Such different tube lengths may be advantageous, for example, if the dip tube 14 is more expensive than the extension tube 16, or if the dip tube 14 is subject to greater corrosion or wear (due to heat, reactivity with the melt 50, etc.) than the extension tube 16, requiring more frequent replacement. In this particular example, the length of the dip tube 14 is about 5 cm and the length of the extension tube 16 is about 2 m, so that the (extended) length of the extension tube 16 reduces the length of the dip tube 14 to reach the melt 50. Many alternative suitable lengths of the dip tube 14 and extension tube 16 may be used, and other embodiments may provide tubes of the same or similar lengths.

[0068] The extension tube 16 has a similar coefficient of thermal expansion as the dip tube 14. As known to those skilled in the art, the coefficient of thermal expansion can reflect a strain value with respect to temperature, with a material having a lower coefficient of thermal expansion having a lower strain value (due to a higher adhesive strength). Thus, in this context, materials having a similar coefficient of thermal expansion can include any two or more materials having a similar bond structure, or any two or more materials having different bond structures but similar expansion and / or strain characteristics. Furthermore, in this context, materials having a low coefficient of thermal expansion can include any material that falls at the lower end of the thermal expansion scale at a particular temperature (e.g., above 1500°C). In this particular embodiment, the dip tube 14 and the extension tube 16 are manufactured from one or more different heat-resistant materials having a low coefficient of thermal expansion. Thus, these one or more different heat-resistant materials also exhibit a low strain value, thereby ensuring a low expansion pressure on the joint between the dip tube 14 and the extension tube 16, and thus the connection 22.

[0069] The submerged tube 14 and the extension tube 16 may be made of one or more different heat-resistant materials and may be able to withstand at least 1500°C without significant loss of mechanical strength or corrosion or other degradation, and therefore be usable for at least a predetermined period of time (e.g., a single thermal melting cycle, or at least two melting cycles). A number of different heat-resistant materials and / or combinations of materials may be suitable for different embodiments, including, but not limited to, non-porous ceramics and high melting point metals. In effect, the submerged tube 14 and / or the extension tube 16 may be made of one or more different heat-resistant materials that can withstand at least 1500°C, allowing the heat-resistant lance assembly 10 to be utilized in melts having high melting temperatures. However, only the submerged tube 14 in this embodiment is able to withstand at least 1500°C due to the fact that it is at least partially insertable into the melt 50 (indeed, only the submerged end 14.1 is submerged). In embodiments where the submerged tube 14 includes multiple components, only the component inserted into the melt may need to be able to withstand at least 1500° C. This may include, for example, only the submerged end 14.1.

[0070] In this embodiment, both the submerged tube 14 and the extension tube 16 are fabricated from one or more refractory materials that are resistant to corrosion and thermal shock. Such characteristics allow for the use of the refractory lance assembly 10 in applications that employ corrodible metals and / or that require extreme heat and / or repeated thermal cycling. The term "corrosion" in this context can again be broadly interpreted, as indicated above. Corrosion can include, for example, the formation and / or propagation of microcracks in the submerged tube 14 and the extension tube 16. In other examples, corrosion can include oxidation of one or more refractory materials. While the submerged tube 14 can be thermally shocked during insertion into the melt 50, the extension tube 16 can be thermally shocked when brought into the vicinity of and / or into a furnace containing the melt 50 (although not generally inserted into the melt 50, as shown). When the refractory lance assembly 10 is moved from an external environment, typically at atmospheric pressure, into a furnace and / or into a melt 50 at temperatures in excess of 1500° C., one or both of the submerged tube 14 and the extension tube 16 may be subjected to thermal shock. In order to maintain the mechanical and / or chemical stability of the refractory lance assembly 10, both the submerged tube 14 and the extension tube 16 may need to be resistant to thermal shock.

[0071] The refractory material(s) of the submerged tube 14 and the extension tube 16 may have different corrosion and thermal shock resistance properties. In particular, the submerged tube 14 is at least partially insertable into the melt 50 at the submerged end 14.1 and may have higher corrosion and thermal shock resistance in contrast to the extension tube 16, which is typically spaced from (and not inserted into) the melt 50 by the length of the submerged tube 14. The refractory material(s) of the submerged tube 14 may be sufficiently resistant to corrosion and thermal shock to be inserted into a melt at a temperature above 1500° C. On the other hand, the refractory material(s) of the extension tube 16 may be sufficiently resistant to corrosion and thermal shock to withstand temperatures just above the melt 50 (i.e., not inserted into the 1500° C. melt 50) and is typically disposed at least partially within a furnace in use.

[0072] In this particular embodiment, the second end 14.2 of the dip tube 14 snugly receives therein the first end 16.1 of the extension tube 16. The dip tube 14 and the extension tube 16 have respective outer and inner diameters to achieve this snug fit. This snug fit may form an interference fit and may form part of the connection 22, at least partially sealing the joint between the dip tube 114 and the extension tube 16. In other embodiments, the second end 14.2 of the dip tube 14 may be snugly received within the first end 16.1 of the extension tube 16. In yet other embodiments, the dip tube 14 and the extension tube 16 have similar diameters, with the ends of the respective tubes abutting flush with each other and with the connection 22 connecting them. Indeed, a variety of connections of the composite tubes 12 are envisioned without departing from the general nature and scope of the present disclosure.

[0073] Turning now to the dip tube 14 (sometimes referred to as the "dip probe"), as shown, the submerged end 14.1 (first end) of the dip tube 14 is at least partially insertable into the melt 50. The dip tube 14 may have a length that allows the shroud 18 and the connection portion 22 to be removed from temperature exposure resulting from or caused by the melt 50 and / or the furnace into which the refractory lance assembly 10 is inserted during use. In particular, neither the shroud 18 nor the connection portion 22 are inserted into or in any way contact the melt 50. Advantageously, by ensuring that the shroud 18 and the connection portion 22 remain removed from the melt 50, these components may have lower heat resistance, corrosion resistance, and / or thermal shock resistance compared to the dip tube 14, and particularly compared to the submerged end 14.1.

[0074] In this embodiment, the dip tube 14 comprises a non-porous ceramic cylinder with a submerged end 14.1 defined at its lower end. Non-porous ceramics typically have a low coefficient of thermal expansion, high mechanical strength at high temperatures, and both corrosion and thermal shock resistance. Non-porous ceramics have the additional potential advantage of generally being impermeable. In this embodiment, the cross section of the dip tube 14 is circular, but it should be understood that in other embodiments, various other shapes (e.g., square, triangular, rectangular, polygonal) and / or dimensions of the dip tube 14 may be envisioned. A greater thickness of the non-porous ceramic cylinder 14 provides greater corrosion resistance, and a smaller thickness provides less corrosion resistance, so the thickness of the non-porous ceramic cylinder 14 may be selected based on the particular intended application of the refractory lance assembly 10. In this embodiment, the non-porous ceramic cylinder 14 has a thickness of about 2-3 mm, an inner diameter of about 20 mm, and an outer diameter of about 25 mm-30 mm, specifically 24 mm-26 mm. The outer diameter of the solid ceramic cylinder 14 is such that it can mate with the extension tube 16, specifically, a slip fit over the first end 16.1 of the extension tube 16, as described above.

[0075] In this embodiment, the non-porous ceramic cylinder 14 comprises zirconia silicate boron nitride (ZSBN), which comprises 45% zirconium dioxide (zirconia) in a matrix of boron nitride and borosilicate glass. ZSBN is corrosion resistant and has excellent thermal shock resistance, even at temperatures above 1500°C. In particular, the combination of zirconia, boron nitride, and borosilicate glass in ZSBN may exhibit properties and / or characteristics superior to one or more of the individual components alone, particularly with respect to enhanced corrosion and thermal shock resistance. In particular, in this embodiment, ZSBN combines the corrosion resistance of zirconia with the thermal shock resistance of boron nitride, thereby producing a heat-resistant material that has a low coefficient of thermal expansion, can withstand 1500°C, and is resistant to both corrosion and thermal shock.

[0076] However, as noted above, any suitable material having a low coefficient of thermal expansion, including, for example, non-porous ceramics, may provide a viable alternative to ZSBN for the dip tube 14. In other embodiments, the non-porous ceramic cylinder 14 may include, for example, boron nitride, boron nitride with at least 40% zirconium dioxide (zirconia), or ZSBN, but with a different percentage of zirconia and / or a different matrix composition.

[0077] The ZSBN composition of the dip tube 14 in this embodiment is advantageous, at least in part, over the prior art using typical non-porous ceramics, and may be an obvious alternative to porous ceramics conventionally used to manufacture lances insertable into molten materials, which typically lose structural integrity and melt at higher temperatures. For example, Sialon and Sialon II are viable non-porous ceramics up to about 1000°C to 1200°C, but exposure to temperatures above this range may cause the lance to lose structural integrity and melt. Other conventionally used synthetic materials may not be able to withstand repeated thermal cycling. For example, fused silica appears to be able to withstand high temperatures, but when tested, it can only withstand thermal cycling at high temperatures for a few minutes. Still other conventionally used materials may not provide sufficient corrosion resistance at such high temperatures. For example, silicon carbide and graphite appear to have adequate thermal shock resistance, but lack corrosion resistance and melt in molten steel within minutes. Zirconia and magnesia, by themselves, are corrosion resistant, but have poor thermal shock resistance, which typically results in cracks or other damage to the lance during use. Similarly, alumina, by itself, is corrosion resistant, but not thermal shock resistant. However, the ZSBN of the present embodiment can have a low coefficient of thermal expansion, allowing the dip tube 14 to maintain structural integrity at high temperatures, particularly temperatures above 1500° C., and is resistant to both corrosion and thermal shock.

[0078] In another specific embodiment of the present disclosure (not shown), the dip tube 14 comprises a ceramic cylinder coated with an insulating non-porous ceramic layer on at least one end of the ceramic cylinder that is inserted into the melt 50. In this embodiment, the insulating non-porous ceramic layer serves to insulate the ceramic cylinder, reducing the thermal shock experienced by the ceramic cylinder when inserted into the melt, and can maintain the structural integrity of the ceramic cylinder. In this embodiment, the insulating non-porous ceramic layer extends several inches along the length of the ceramic cylinder. In one embodiment, the ceramic cylinder is fabricated from aluminum oxide (alumina) and the insulating non-porous ceramic layer comprises zirconia silicate boron nitride (ZSBN), which comprises 45% zirconium dioxide (zirconia) in a matrix of boron nitride and borosilicate glass. However, the insulating non-porous ceramic layer may comprise one or more other heat-resistant non-porous ceramics capable of withstanding at least 1500°C, and particularly resistant to corrosion and thermal shock at such temperatures, such as boron nitride, boron nitride with at least 40% zirconium dioxide (zirconia), or ZSBN with various compositions. One advantage of this alternative embodiment over the specific embodiment described above is that less material may be required that can withstand 1500°C and has sufficient corrosion and thermal shock resistance. Specifically, only the insulating non-porous ceramic layer on the ceramic cylinder is required, not the entire tube. If the appropriate non-porous ceramic material is expensive, it may be economically viable to coat another tube with the non-porous ceramic material. The ceramic cylinder is typically coated on the outside with an insulating non-porous ceramic layer to prevent corrosion when splashes of material from the melt reach the ceramic cylinder. Further techniques for improving adhesion of the insulating non-porous ceramic layer to the ceramic cylinder may be used during construction of the dip tube, such as by mesh bonding, which are intended to be well within the general scope and nature of the present disclosure. Additionally, it should be understood that in other embodiments, the insulating non-porous ceramic layer may simply coat the dip end 14.1.

[0079] Returning to this embodiment and with continued reference to FIG. 1, the connection 22 is removable and the dip tube 14 is replaceable with one or more alternative dip tubes (not shown). In this embodiment, the one or more alternative dip tubes have the same composition as the dip tube 14 and include ZSBN tubing. In other embodiments, the composition of the one or more alternative dip tubes is similar to or different from the dip tube 14, depending, for example, on the intended use. The dip tube 14 and the one or more alternative dip tubes may include tubing of various lengths to provide lengths of alternative dip tube 14 connectable to the extension tube 16 by the connection 22 for different intended uses, etc.

[0080] Turning now to the extension tube 16 (sometimes referred to as a "submerged lance" or "lance extender"), the extension tube 16 is sufficiently corrosion resistant to be reusable for two or more thermal cycles involving temperatures in excess of 1500°C. As noted above, the extension tube 16 has a similar coefficient of thermal expansion as the submerged tube 14. Because the submerged tube 14 in this example comprises ZSBN, the extension tube 16 has a low coefficient of thermal expansion similar to that of ZSBN. In this embodiment, the extension tube 16 comprises a non-porous metal cylinder, thereby preventing gas from entering the optical path during use. Indeed, the non-porosity of the metal also contributes to the corrosion resistance of the extension tube 16. Most metals are also inherently thermal shock resistant.

[0081] In this embodiment, the cross section of the extension tube 16 is circular, however, it should be understood that for other embodiments, various other shapes (e.g., square, triangular, rectangular, polygonal) and / or dimensions of the extension tube 16 may be envisioned. Furthermore, the shape and / or dimensions of the extension tube 16 need not match the dip tube 14. The thickness of the metal cylinder 16 may be selected based on the particular intended application of the heat resistant lance assembly 10, as a thicker metal cylinder 16 provides greater corrosion resistance and a thinner metal cylinder provides less corrosion resistance. In this embodiment, the metal cylinder 16 is approximately 2-3 mm thick, has an inner diameter of 24-26 mm, and an outer diameter of 28-32 mm, and may be fitted with the dip tube 14 by fitting the slip-fit ​​dip tube 14 inside the second end 14.2 of the dip tube 14, as described above.

[0082] In this embodiment, the metal cylinder 16 specifically comprises molybdenum. Molybdenum (Mo) has a melting point of 2622°C and is relatively stable. In other embodiments, the metal cylinder 16 may be comprised of other suitable metals, including, for example, chromium, iridium, niobium, osmium, tungsten, tantalum, or suitable alloys of molybdenum or any of the aforementioned metals. In yet other embodiments, the extension tube 16 comprises a non-porous ceramic cylinder, for example made of Sialon and / or Sialon II. In yet another embodiment, the extension tube 16 may comprise a metal cylinder coated with a non-porous ceramic or the like.

[0083] Turning now to the connection 22, in this embodiment, the connection 22 is made of a heat resistant material. As indicated above, the connection 22 may not require the same heat resistance as the dip tube 14, but in this embodiment, the connection 22 can withstand the heat in a furnace. In particular, the connection 22 in this example is made of borosilicate or calcium borate.

[0084] In this particular embodiment, as shown in FIG. 1, the connection 22 comprises a tube connector in the form of a ferrule disposed between the dip tube 14 and the extension tube 16. The ferrule 22 has a female threaded surface (not shown) that engages a complementary male threaded surface (not shown) of the dip tube 14 and the extension tube 16. Thus, in this embodiment, the dip tube 14 and the extension tube 16 (which fit together) are received inside the ferrule 22 on the other side, such that the ferrule 22 forms a sleeve or sheath that covers the joint between the dip tube 14 and the extension tube 16. Advantageously, this arrangement at least partially seals the joint and prevents air contamination from entering the optical path of the compound tube 12, potentially altering the representative surface of the bulk melt and / or the optical measurements taken by the optical sensing system ("LIBS"). The compound tube 12 can therefore be described as being substantially impermeable, or in other words, insulated. In some embodiments, the connection 22 may include one or more seals to further seal the joint between the ferrule and one or both of the dip tube 14 and extension tube 16 .

[0085] As noted above, in this embodiment, the connection 22 (specifically a ferrule) defines a removable connection between the dip tube 14 and the extension tube 16. Advantageously, such a removable connection 22 allows for the dip tube 14 to be replaced with a first replacement tube from one or more alternative dip tubes (not shown) when the dip tube 14 corrodes or wears, and then the first replacement tube to be replaced with a second replacement tube from the one or more alternative dip tubes. Thus, in this embodiment, the heat resistant lance assembly 10 provides an assembly that is reusable for two or more thermal cycling rounds.

[0086] In other embodiments of the refractory lance 10 not illustrated herein, a plurality of stacked ferrules may form the tube connector 22, serving the similar function of joining the dip tube 14 and the extension tube 16 and forming an insulating sleeve. In other embodiments, also not illustrated herein, the connection 22 may include a bond in the form of a ceramic-based bond, including, for example, any one of borosilicate or calcium borate, which is intended to be well within the general scope and nature of the present disclosure. If a bond is provided as the connection 22, the dip tube 14 is securely attached to the extension tube 16 and cannot be replaced (or can only be replaced with an additional bond dissolution step). In other embodiments, the connection 22 may include one or more fasteners. The one or more fasteners may include one or more of a nut and key, or similar fastening means. In some embodiments, the connection 22 may include a fastener (nut or key) in addition to the one or more ferrules to provide a secure connection between the dip tube 14 and the extension tube 16. Various other elements and configurations of the connection 22 are feasible in further embodiments and are intended to be within the nature and scope of the present disclosure. In some embodiments, the connection 22 can form at least a partial seal at the junction, but the connection 22 need not form a sealed connection (or an impermeable seal) between the dip tube 14 and the extension tube 16, as other complementary functions may be equivalent.

[0087] Turning now to the optical path, in this embodiment, the optical path provides an unobstructed path through the compound tube 12 through which an optical sensing means of an optical sensing system ("LIBS") can optically probe or otherwise obtain optical measurements from the melt 50 during use. In this embodiment, as shown in FIG. 1, the optical path further defines a gas channel or flow path, which allows for a flow of an inert gas that is released during use through the compound tube 12 into the melt 50 at the first end 14.1 of the dip tube 14 to form a bubble 52 from which an optical measurement can be measured by the optical sensing system. That is, an inert gas can be injected through the compound tube to form a melt surface (e.g., an inner surface of the bubble 52) that is immersed in the melt, which isolates the optical probing of the melt 50 from this immersed melt surface under exposure to the injected inert gas. That is, optical measurements can be obtained from the inner immersed melt surface of the bubble 52 formed by the inert gas in the melt 50, which can more accurately reflect the composition of the melt 50. As mentioned above, the gas that generates the bubbles in the melt 50 may be an inert gas, such as argon, that is not reactive with or contaminating the melt 50. The argon may further function to remove contaminating particulate matter from the optical path, thereby maintaining accurate optical measurements. In this embodiment, as shown, the argon enters the gas channel through an inlet 17 located at the top end of the refractory lance assembly 10. This inlet 17 may be connectable to an upstream source of pressurized inert fluid (not shown). In some embodiments, not shown herein, the refractory lance assembly 10 may include means for controlling the flow of an inlet gas, such as argon, into the gas channel defined by the composite tube 12. In particular, some embodiments may have means for keeping the pressure in the gas channel relatively constant. Such means may include a pressure valve or the like.

[0088] Turning now to the shroud 18, in this embodiment, the shroud 18 is connected to the compound tube 12 by two or three threads (although various means for connecting the shroud 18 to the compound tube at least at one end are contemplated). Advantageously, during use, if the compound tube 12 (whether the dip tube 14, extension tube 16 or connection 22) breaks, cracks or other damage occurs, which creates a leak or breaks a seal, a pressure difference (similar to the Venturi effect) may allow the inert gas in the containment volume 20 to pass therethrough and enter the optical path in the compound tube 12. Thus, as will be further explained below, in this embodiment where the extension tube 16 contains a metal and the dip tube 14 contains a ZSBN, the pressurized inert gas surrounding the connection 22 in the containment volume 20 may compensate for the difference in natural expansion between the metal and the ZSBN, thereby avoiding contamination of the optical path of the compound tube 12 through which optical measurements are taken.

[0089] It should be appreciated that the at least partial seal resulting from the pressurized inert gas in the containment volume 20 can reduce the requirement of the connection 22 to seal the joint. In particular, while the connection 22 can at least partially seal the joint, the pressurized inert gas in the containment volume 20 can be supplemented by the application of an external positive pressure, so that if the connection 22 does not form a seal or if a leak occurs at the connection 22, the pressurized inert gas in the containment volume 20 can pass therethrough (or be absorbed) into the optical path to avoid air contamination of the optical path (which may contaminate a representative surface of the molten bulk). Thus, the shroud 18 and the pressurized inert gas in the containment volume 20 in use can form a secondary sealing means for the composite tube 12 in addition to the connection 22.

[0090] In this embodiment, as described above and shown in FIG. 1, the shroud 18 is a cylindrical body that houses or encloses the composite tube 12, specifically the extension tube 16, the connection 22 and the upper portion 14.2 of the dip tube 14. In this embodiment, the inside diameter of the shroud 18 is about 40 mm to 50 mm. The shroud 18 is manufactured from one or more heat resistant materials, but does not need to have the same corrosion resistance and / or thermal shock resistance as the dip tube 14, since the shroud 18 is not inserted into the melt 50 in normal use. The dip tube 14 extends beyond the lower end of the shroud 18 such that the shroud 18 is positioned in a spaced apart position above the melt 50 in use.

[0091] The containment volume 20 is formed between the composite tube 12 and the shroud 18 as described. The volume of the containment volume 20 is therefore dependent on the respective volumes of the composite tube 12 and the shroud 18. The shroud 18 is coaxially aligned around the composite tube 12 to define the containment volume 20 therebetween. In particular, in some embodiments, the containment volume 20 may need to be of a shape and size sufficient to apply a positive pressure at least to the connection 22 when the inert gas is received therein. The refractory lance assembly 10 in this embodiment includes an inlet 24 disposed within the shroud 18 through which the pressurized inert gas is received into the containment volume 20. The inlet 24 is connectable to an upstream source of pressurized inert gas (not shown). The refractory lance assembly 10 in this embodiment further includes an outlet 26 disposed within the shroud 18, specifically at a lower end thereof, through which the pressurized inert gas is discharged from the containment volume 20 to the external environment (outside the refractory lance assembly 10). Thus, in this embodiment, containment volume 20 may specifically be considered a void. Any pressurized inert gas released from containment volume 20 via outlet 26 may fall or sink to the top surface of melt 50, thereby further reducing the oxidation potential of the upper exposed layer of melt 50. In an embodiment, the accuracy of optical probing performed using LIBS may be further improved.

[0092] In this particular embodiment, as described above, the pressurized inert fluid comprises a gas, specifically argon (Ar), and the upstream pressurized inert fluid source comprises a pressurized argon source. Thus, as shown in this embodiment, the refractory lance assembly 10 includes two argon-containing channels or argon flow paths, one that traverses the optical path and generates gas bubbles in the melt 50, and the other that seals the junction between the dip tube 14 and the extension tube 16. While this embodiment utilizes argon in both channels or paths, it should be understood that in other embodiments any inert fluid (and potentially different fluids in each channel) may be viable. Additionally, it should be understood that argon gas is heavier than air and therefore would be expected to fall downward upon exiting the outlet 26 as described above. Other relatively heavy inert gases may also be suitable for this purpose. Additionally, argon gas has a low thermal conductivity and is therefore a better insulator compared to, for example, air. Other relatively insulating monatomic gases, or combinations of gases, may also be suitable for this purpose.

[0093] One advantage of this embodiment may include that the refractory lance assembly 10 does not require a cooling mechanism or cooling fluid to withstand temperatures in excess of 1500° C. Both the composite tube 12 and the shroud 18 may be fabricated from refractory materials such that at least the submerged tube 14, or at least the submerged end 14.1, can withstand temperatures in excess of 1500° C. Thus, the pressurized inert gas, which in this embodiment is argon, does not need to be cooled to cool the refractory lance assembly 10. However, it should be understood that while compressed argon gas may provide a relatively low level of cooling in some embodiments, it is not necessarily required for the operation of the refractory lance assembly 10.

[0094] Turning now to the optical detection system, in this embodiment, the optical detection system comprises a Laser Induced Breakdown Spectroscopy (LIBS) system, as shown in FIG. 1. More specifically, the heat-resistant lance assembly 10 may be mechanically connected to a LIBS system mounted on an optical window to obtain optical measurements in the form of LIBS composition measurements from the melt 50. The LIBS system may comprise, for example, a laser source for emitting short, intense laser pulses (e.g., flash lamp pumped or diode-pumped solid-state laser source with active Q-switching), an optical window through which the laser is emitted, detection means (e.g., a line or 2D camera, or an intensified charge-coupled device camera) provided on the same side of the optical window as the laser, and at least one spectrometer for extracting spectral information from the detected radiation. Any elements forming part of such mechanical connection to the LIBS system may be heat resistant and even capable of withstanding temperatures in excess of 1500° C. Components that may form part of such mechanical connection may include, for example, collars, fasteners, seals, etc.

[0095] Thus, those skilled in the art will generally appreciate the sensitivity of LIBS systems and the advantages offered by both the connection 22 and the containment volume 20 used in conjunction with pressurized inert gas (specifically argon) that can enter the optical path of the compound tube 12 in the event of a crack, leak, or the like occurring during use, ensuring that the optical path of the compound tube 12 is not contaminated by any air.

[0096] In use, the refractory lance assembly 10 may require pre-heating before inserting the dip tube 14 into the melt 50, for example to prevent thermal shock. In this embodiment, the refractory lance assembly 10 is pre-heated by placing the dip tube 14 in a position directly above the melt 50 (typically only a few millimeters above) in a furnace and holding the refractory lance assembly 10 in that position for a predetermined period of time before slowly inserting the first end 14.1 (specifically the submerged end) of the dip tube 14 into the melt 50 to begin bubbling and obtain LIBS composition measurements. This pre-heating of the refractory lance assembly 10 may be performed prior to operating the LIBS system to which the refractory lance assembly 10 is connected.

[0097] The LIBS composition measurements obtained for the melt 50 (specifically the submerged melt surface of the bubble 52) may include, for example, elemental composition and / or concentration expressed as percentages or other values, etc., which may be presented to an operator as a spectral signature or may be further processed in another manner. The composition measurements may inform an operator whether the operating conditions are to produce a desired result (e.g., with reference to the composition and / or concentration of the melt) or whether adjustment of one or more operating conditions, such as temperature, is required. The LIBS composition measurements may also include composition measurements from one or more inclusions (not shown) in the melt 50. The inclusions typically include extrinsic inclusions, which in this example may originate from, for example, slag, and intrinsic inclusions that arise during the melting process. In particular, the inclusions may include iron oxide, copper oxide or nickel oxide, or other solid intermetallic compounds that do not dissolve in the melt 50. Such inclusions may include non-metallic inclusions. Obtaining LIBS composition measurements from one or more inclusions in the melt 50 can be indicative, at least in part, of the purity or cleanliness of the melt 50. In particular, in this embodiment, through the refractory lance assembly 10 in combination with a LIBS system, not only the presence of inclusions can be identified, if desired, but also the specific composition of the inclusions. Identifying the composition of the inclusions can provide information regarding the melting process, such as the specific temperature to which the melt 50 should be exposed to reduce the inclusions.

[0098] In this embodiment, the melt 50 comprises at least a partially molten metal. For example, the at least partially molten metal may be one or more of iron, steel, nickel, copper, platinum, and alloys thereof. A particular application of the refractory lance assembly 10 is envisioned in the steel industry where melting temperatures in excess of 1500° C. are required. For example, the refractory lance assembly 10 may be utilized in the secondary metallurgy of steelmaking. However, as will be appreciated by those skilled in the art with reference to this disclosure, the refractory lance assembly 10 may be used to obtain LIBS composition measurements from any metal having a high melting temperature. The refractory lance assembly 10 may be particularly useful, for example, in molten ferrous metals that may be prone to oxidation, which in turn may affect sensitive LIBS measurements. However, as shown, during use, only the end or tip of the submerged tube 14 is submerged in the melt 50, and that end or tip typically comes into contact with molten slag before reaching the molten metal.

[0099] In this embodiment, the LIBS system further comprises an additional spectrometer configured to monitor oxygen spectral lines (as part of the spectral profile) in the melt 50 (specifically, at the submerged melt surface of the gas bubble 52). The oxygen spectral lines, in some embodiments, will be indicative of oxide formation in the melt 50, specifically on the inner surface of the gas bubble 52 in the melt 50. Knowing the oxygen (O2) concentration is relevant to inform an operator that potential oxidation is occurring (which may affect the accuracy of the LIBS system) so that the operator can take steps to prevent oxidation of the melt 50 while the LIBS composition measurements are being taken. Besides that, if applicable, knowing the oxygen concentration may be relevant to inform an operator of expected melt properties for the melt 50 during or after thermal cycling.

[0100] In this embodiment, the LIBS system may specifically utilize the 247.8 nm spectral line to measure carbon (C) concentration in steel, which is important in achieving desired properties of, for example, alloy steels and cast irons. As known to those skilled in the art, carbon in steel can include mass fractions from less than 0.001% (or 10 μg / g) to more than 2%, making spectrochemical measurement at low levels difficult, especially in that the most sensitive lines are in the vacuum ultraviolet (VUV) wavelength region, requiring detection systems suitable for these wavelengths, as well as vacuum or inert gas conditions to avoid strong absorption of radiation. As mentioned above, the dip tube 14 of the heat-resistant lance assembly 10 is inserted directly into the melt 50, thereby minimizing the distance between the melt surface and the detector, and as mentioned above, the composite tube 12 is filled with argon to generate bubbles in the melt 50, minimizing oxidation of the melt surface. Advantageously, using the 247.8 nm line instead of, for example, the 193 nm line may allow for the use of longer optical fibers. In particular, it is known that in atomic spectroscopy, carbon can be detected by atomic emission spectroscopy by monitoring the 193.1 nm or 247.8 nm carbon lines. However, 247.8 nm suffers from interference from iron lines, and 193 nm is free of interference but absorbed during transmission through optical fibers in LIBS. To use 247.8 nm, a separate iron line with the same excitation level as the 247.8 carbon line can be utilized, and the 247.8 nm carbon line can be subtracted from the interfering line, allowing it to be used in optical fibers instead of relying on the 193 nm carbon line.

[0101] As mentioned above, a particular application of the refractory lance assembly 10 is envisioned in the steel industry. For example, the refractory lance assembly 10 can be utilized in secondary steelmaking metallurgy, such as ladle metallurgy (LMF) and vacuum degassers (VD). Because the refractory lance assembly 10 can withstand the temperatures required for these processes, real-time continuous composition measurements can better capture alloy and flux usage trends, thus leading to significant savings over time before the batch is completed, as well as eliminating the turnaround time required to obtain and analyze each sample. To illustrate this, consider a typical batch with a 40 minute cycle time, of which 4 minutes are required to obtain and analyze samples before the next process decision is made. In such a scenario, productivity improvements of up to 10% are possible if real-time continuous composition measurements can be obtained using the LIBS-connected refractory lance assembly 10. The LIBS-connected refractory lance assembly 10 can be particularly useful in VD, which generally cannot be physically sampled under vacuum. In another example, the refractory lance assembly 10 may be used in blast furnace steelmaking, specifically for compositional measurement of hot metal or pig iron in blast furnace runners, where savings may be achieved through reduction in average hot metal silicon (Si) for hot metal production. These uses and advantages are applicable to the composite tube 12 itself, the refractory lance assembly 10, and any of the other embodiments described herein.

[0102] 2-6, a refractory lance assembly, generally referred to using the numeral 200, will be described in accordance with a further exemplary embodiment. The refractory lance assembly 200 in this embodiment is primarily similar to the exemplary embodiment of FIG. 1, and therefore common features are omitted as much as possible for the sake of brevity. In this embodiment, the refractory lance assembly 200 includes a composite tube 108 (best shown in FIG. 3) that is substantially resistant to corrosion and thermal shock at temperatures of 1500° C. or greater. The composite tube 108 defines an optical path 110 therethrough and includes a dip tube 102 (or first tube) having a first end 102.1 insertable into the melt, and a second end (opposite the first end) connected to an extension tube 104 (or second tube) extending longitudinally therethrough, and a connection 106 disposed at the junction between the dip tube 102 and the extension tube 104 to at least partially seal the junction.

[0103] The heat resistant lance assembly 200 further comprises a shroud 202 (or sleeve) surrounding at least the junction between the dip tube 102 and the extension tube 104 at the spaced apart position and defining a containment volume 204 (or gap) between the compound tube 108 and the shroud 202, and receiving pressurized inert fluid therein such that in the event of a leak occurring in the compound tube 108 during use, said pressurized inert fluid can enter the optical path 110 from the containment volume 204, thereby preventing contamination of said optical path 110 and maintaining consistent measurements. In this embodiment, the shroud 202 is again shown covering the extension tube 104, the connection 106 and the second end of the dip tube 102. In some embodiments, not shown herein, the shroud 202 can further include one or more seals. For example, forming an airtight seal between the shroud 202 and the dip tube 102. 1, this assembly can at least partially seal the joint between the dip tube 102 and the extension tube 104, typically covering at least an inch of the dip tube 102 below the connection 106. However, other embodiments are envisioned in which the shroud 202 does not completely encase or cover the connection 106 or dip tube 102, and the connection 106 is expected to maintain an adequate seal.

[0104] In this embodiment, the dip tube 102 and the extension tube 104 have similar coefficients of thermal expansion. The dip tube 102 is made entirely of a non-porous ceramic in the form of zirconia silicate boron nitride (ZSBN), which contains approximately 45% zirconia in a matrix of boron nitride and borosilicate glass, and the extension tube 104 (which is longer than the dip tube) comprises a metal cylinder made of molybdenum. In this particular embodiment shown in Figures 2-6, the dip tube 102 and the extension tube 104 have similar diameters, and the ends of the respective tubes 102, 104 are flush and adjacent to one another. The refractory lance assembly 10 may include one or more seals at this joint between the dip tube 102 and the extension tube 104.

[0105] In this embodiment, composite pipe 108 further comprises a coupler 106 disposed at the junction between the dip tube 102 and the extension tube 104 in the form of a pipe connector that receives each end of the dip tube 102 and the extension tube 104 therein to form an insulating sheath around the junction. Pipe connector 106 is fabricated from either borosilicate or calcium borate.

[0106] In this embodiment, the inlet to the optical path 110 is indicated at 206 and is where, in this embodiment, argon gas is injected into the refractory lance assembly 200. However, in this embodiment, the shroud 202 is closed or sealed at the end proximate the dip tube 102 such that the containment volume 204 has a fixed or defined volume. As shown, the refractory lance assembly 200 further comprises an outlet, indicated at 208. In this embodiment, the outlet 208 comprises a one-way pressure valve that releases argon gas from the volume 204 to maintain the pressure within the containment volume 204 at a predetermined constant value.

[0107] In this embodiment, the numeral 300 broadly refers to the mechanical connections used to connect the refractory lance assembly 200 to a LIBS system. It should be understood that the mechanical connections 300, and the portions of the refractory lance assembly 200 enclosed in the "E", are variable depending, for example, on the particular LIBS system to which the refractory lance assembly 200 is connected.

[0108] 7-9, these graphs show the comparability of composition measurements obtained on melts using conventional laboratory techniques ("Lab Analysis") and using a refractory lance assembly connected to a LIBS system according to another embodiment. The refractory lance assembly used in these experiments has similarities to the embodiment shown in the previous figures, but is not identical.

[0109] 7 and 8 show the results of a two-day test on a laboratory-scale experimental setup set up for steelmaking applications, as described above, specifically demonstrating the utility of measuring silicon (Si) or manganese (Mn) in pig iron. The experimental setup consisted of an induction furnace for holding the molten pig iron, and a refractory lance assembly 10 connected to a LIBS system and placed above the induction furnace via a crane, according to one embodiment. The probe of the LIBS system consisted of a Q-switched Nd:YAG pulsed laser providing 300 mJ of energy per pulse at a wavelength of 1064 nm. The optical fiber of the LIBS system allowed the radiation emitted from the plasma to be collected and remotely analyzed using a commercially available spectrometer. In this case, a 55 cm focal length Czerny-Turner spectrometer with a 3600 lines / mm grating and an intensified charge-coupled device (CCD) camera were used to measure Si I at 288.16 nm and Mn II at 293.31 nm. In addition, the probe contained a custom-built vacuum ultraviolet (VUV) spectrometer to measure carbon at 193.09 nm. Below wavelengths of about 200 nm, the radiation was further blocked by oxygen in the air and by optical fibers. Therefore, to measure these wavelengths, a spectrometer was installed with a direct line of sight to the plasma.

[0110] In this experiment, the procedure involved melting an initial charge of approximately 35 kg of pig iron in an induction furnace. The molten hot metal contained initial concentrations of approximately 0.15 wt% Si and 0.01 wt% Mn. The molten charge was heated to a temperature between 1480°C and 1530°C (measured by bath temperature measurement). A refractory lance assembly 10, specifically the end or tip of the dip tube, was then lowered by crane and placed approximately 2 inches above the melt for several minutes for preheating (no other preheating method was used). After preheating, the end or tip of the dip tube was inserted into the melt and the LIBS system probe was activated to flow argon into the composite tube to generate gas bubbles in the melt and compositional measurements were taken for at least 10 minutes, irradiating the bubble's inner surface with a frequency of 2 laser pulses per second (2 Hz). After this, the dip tube was removed from the bath. Bath samples were taken for conventional laboratory compositional analysis, specifically for solid-state optical emission spectroscopy (OES), and temperature measurements were taken to ensure a constant bath temperature. This was followed by bath additions of iron(II) sulfide (FeSi) and iron manganese (FeMn) to increase the concentration of the elements of interest, with some time allowed for the additions to become homogenous in the melt. This procedure was repeated several times (usually at least six additions), terminating after approximately two hours of run time at maximum temperature to ensure sufficient furnace lining integrity and safety.

[0111] As mentioned above, Figures 7 and 8 show, among other things, the results of the two-day test as calibration curves. In both figures, the upper dotted curve reflects the Si / Fe signal and the lower dotted curve reflects the Mn / Fe signal, as indicated therein. As stated, the horizontal axis reflects the concentration (wt%) of elemental Si and Mn in the melt measured with conventional sampling techniques. The vertical axis reflects the concentration of elemental Si and Mn measured directly with a refractory lance assembly connected to a LIBS system, shown as the ratio of the photon counts measured at characteristic spectral lines. The photon counts measured at two selected Si and Mn spectral lines are divided by the photon count measured at the corresponding Fe spectral line, following known normalization procedures. In both Figures 7 and 8, the dotted curves correspond to a second-order polynomial least-squares fit of the data. The vertical height of the error bars corresponds to two standard deviations (using an average of 100 spectra / 50 s of measurements per data point). The results correspond to a measurement accuracy of ±0.008% for Si measurement and ±0.013% for Mn measurement, respectively.

[0112] Those skilled in the art will appreciate that a calibration curve, once established, is the basis of the LIBS technique. For a given set of reference conditions (LIBS system configuration, optical geometry, approximate melt chemistry and temperature, etc.), the established calibration curve can be used to determine the chemical composition of any system using the photon counts measured at any point by the system. A careful comparison of the calibration curves from the two days shows that they are slightly off. This is expected since changes were made to the experimental setup between the two days. In particular, on the first day (Figure 7), a 29 inch (73.7 cm) long heat-resistant lance assembly was used, and on the second day (Figure 8), a 24 inch (61.0 cm) long heat-resistant lance assembly was used. If all else is kept the same, a shorter heat-resistant lance assembly may change the achieved plasma temperature and relative photon emission intensity since the laser pulse of the LIBS laser is concentrated on a smaller area. Additionally, the laser focus on the bubble surface was set to a slightly different point between the two measurement days. One skilled in the art will appreciate that for commercial systems, these parameters are held constant or otherwise accounted for via multiple calibration curves (if varying these parameters provides design advantage). Despite this variation, Figures 7 and 8 show the calibration curve trends of the direct relationship between measurements taken with conventional sampling techniques and measurements taken in-line with the disclosed refractory lance assembly and LIBS system.

[0113] FIG. 9 is a graph of compositional measurements, specifically measurements of component concentrations, for a given sample measured according to one embodiment using conventional laboratory techniques (horizontal axis) and LIBS using a refractory lance assembly (vertical axis), again showing comparable results. In this particular laboratory setup, the melt was copper-nickel matte. As indicated in the legend, the different markers reflect compositional measurements measured for different elements of the copper-nickel matte: copper (Cu) - circles, nickel (Ni) - triangles, iron (Fe) - squares, cobalt (Co) - plus signs (+), and sulfur (S) - diamond shapes. The horizontal axis reflects the concentrations of the copper-nickel matte melt measured with conventional laboratory techniques, specifically by obtaining test samples from the copper-nickel matte melt and conditioning the test samples before performing the laboratory analysis. The vertical axis reflects the concentrations measured directly with the refractory lance assembly connected to the LIBS system, i.e., measurements performed continuously in real time. As shown, the trends reflect a direct relationship between measurements taken with conventional sampling and measurements taken in real time with the refractory lance assembly and LIBS system. However, using the refractory lance assembly and LIBS system to obtain measurements in real time improves efficiency by reducing the analysis time to obtain the same results. Reducing the analysis time may reduce energy costs associated with the analysis, particularly associated with maintaining temperatures in the furnace. Additionally, the overall reduction in analysis time available for pyrometallurgical processes by the present disclosure may reduce greenhouse gas emissions.

[0114] 7-9 thus illustrate that embodiments of the refractory lance assembly at least provide a suitable alternative to conventional laboratory techniques for obtaining compositional measurements. Moreover, as will be appreciated by those of skill in the art with reference to this disclosure, embodiments of the refractory lance assembly may be utilized at extremely high temperatures without significant air contamination (which maintains a surface representative of the molten bulk) that would result in different results than conventional laboratory techniques.

[0115] Another aspect of the disclosure (not shown) provides a refractory lance tube comprising a tube having a first end at least partially comprising a non-porous ceramic, which is substantially resistant to corrosion and thermal shock at temperatures of 1500° C. or greater, such that said first end is insertable into a melt at temperatures of 1500° C. or greater. In a different embodiment, the non-porous ceramic comprises one or more of boron nitride, boron nitride comprising at least 40% zirconium dioxide (zirconia), or zirconia silicate boron nitride (ZSBN) comprising about 45% zirconia in a matrix of boron nitride and borosilicate glass. The refractory lance tube may be received within a shroud or sleeve as described above, whereby the first end projects from the shroud or sleeve to provide a refractory lance assembly.

[0116] Thus, in some embodiments, a heat-resistant lance assembly and a heat-resistant lance tube suitable for use with hot molten materials may be provided. In some embodiments, a heat-resistant lance assembly and a heat-resistant lance tube may be provided that can withstand temperatures of 1500° C. or more. The heat-resistant lance assembly and the heat-resistant lance tube may be sufficiently heat-resistant to not require an active cooling system, improving safety during operation. The heat-resistant lance assembly and the heat-resistant lance tube embodiments may be used in the steel industry and / or in furnaces where temperature control is difficult. In some embodiments, a heat-resistant lance assembly and a heat-resistant lance tube may be provided that is impermeable and exhibits sufficient mechanical strength to avoid the formation of damage, cracks, or leaks during use at high temperatures. Furthermore, in some embodiments, the heat-resistant lance assembly and the heat-resistant lance tube may be resistant to thermal shock as well as to corrosion by molten metal and / or molten slag. In some embodiments, the heat-resistant lance assembly and the heat-resistant lance tube may be substantially chemically stable at high temperatures. For example, the heat resistant lance assembly and heat resistant lance tube may not oxidize at high temperatures. Advantageously, in addition to the aforementioned benefits, the heat resistant lance assembly and heat resistant lance tube may be reusable in some embodiments and may be used repeatedly over multiple thermal cycles. This reusability may potentially reduce costs associated with the LIBS system and / or metal processing and monitoring.

[0117] Further embodiments of the heat resistant lance assemblies and heat resistant lance tubes disclosed herein contemplate that the heat resistant lance assemblies or tubes are provided as part of a heat resistant lance kit (not shown). One exemplary kit may include a dip tube, a removable connection, and multiple variable length extension tubes. Another exemplary kit may include multiple dip tubes, a removable connection, and multiple use extension tubes. The kit may or may not include a shroud or sleeve as disclosed herein in different embodiments.

[0118] It should be understood that the various embodiments of the heat-resistant lance assembly and heat-resistant lance tube disclosed herein may form part of a larger optical sensing or probing system, such as a LIBS system. In one embodiment, a LIBS system may be provided that operates to measure components of a melt at high operating temperatures, comprising any one or more of the heat-resistant lance assemblies (having features similar to any of the above-mentioned embodiments) that are submersible in the melt; a laser source that emits short, intense laser pulses; an optical window through which the laser is emitted into the optical path of the heat-resistant lance assembly; a detection means on the same side of the optical window as the laser; and at least one spectrometer (in some embodiments, multiple spectrometers for extracting different spectral information) for extracting spectral information from the detected radiation. It is envisioned that such a broader LIBS system forms a further aspect of the present disclosure.

[0119] Other embodiments of the present disclosure may be further directed to a method (not shown) for optically probing or measuring the components of a melt. In an embodiment, a method for probing the components of a melt may be provided, the method broadly comprising the following steps: · providing a refractory lance assembly comprising a composite tube and a shroud at least partially housing the composite tube, the composite tube comprising a dip tube, an extension tube, and optionally a coupler therebetween; · preheating the heat resistant lance assembly such that at least the submerged end of the dip tube is preheated; Inserting the immersed end of the dip tube into the melt while simultaneously injecting inert gas between the composite tube and the shroud.

[0120] In some embodiments of the method, an insert gas may also be injected through the composite tube to generate bubbles at the submerged end to form a submerged molten surface for probing. In some embodiments, the method may include replacing the dip tube with a replacement dip tube after it exhibits corrosion, cracks or other wear, and the extension tube is typically reusable for one or more thermal cycles.

[0121] All of the aforementioned advantages ultimately provide a method for obtaining real-time, in-line, and direct (within the molten metal) compositional measurements of molten metal (unoxidized) at high temperatures without the time delays and errors associated with conventional sampling techniques used for such refractory metals.

[0122] The embodiments of the present disclosure offer various advantages over the prior art. The advantages described herein are not intended to provide an exhaustive list, but merely to illustrate at least some of the possible advantages. Those skilled in the art will envision additional advantages and / or applications of the present disclosure that are intended to be well within the general scope and nature of the present disclosure.

[0123] While the present disclosure describes various embodiments for illustrative purposes, such description is not intended to be limited to such embodiments. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents without departing from the embodiments, the general scope of which is defined in the appended claims. No particular order to steps or stages of the methods or processes described in this disclosure is intended or implied, except to the extent necessary or inherent in the process itself. In many cases, the order of process steps can be changed without changing the purpose, effect, or significance of the described method.

[0124] The information shown and described in detail herein is capable of fully achieving the above-mentioned objectives of the present disclosure, the presently preferred embodiments of the disclosure, and is therefore representative of the subject matter broadly contemplated by the present disclosure. The scope of the present disclosure fully encompasses other embodiments that will be apparent to those skilled in the art, and is therefore not limited by anything other than the appended claims, and any reference to an element made in the singular means "one or more," not "one and only," unless expressly stated otherwise. Anything that would be deemed by one skilled in the art to be structurally and functionally equivalent to the elements of the above-mentioned preferred and additional embodiments is intended to be encompassed by the claims. Furthermore, there is no requirement for a system or method to address every problem sought to be solved by the present disclosure, and such problems are encompassed by the claims. Furthermore, no element, component, or method step of the present disclosure is intended to be publicly disclosed, regardless of whether that element, component, or method step is expressly recited in the claims. However, various changes and modifications in shape, materials, article of manufacture, and details of construction, as will be apparent to those skilled in the art, can be made and are encompassed by the present disclosure without departing from the spirit and scope of the present disclosure, as set forth in the appended claims.

[0125] This application claims priority to U.S. Provisional Patent Application No. 63 / 229,749, filed August 5, 2021, and entitled “Heat-Resistant Lance Assembly and Heat-Resistant Lance Tube,” the entire disclosure of which is incorporated herein by reference.

Claims

1. 1. A heat resistant lance assembly for use with an optical detection system for optically probing a melt, comprising: the refractory lance assembly comprising a dip tube having a dip end submersible in the melt, and an extension tube connected to an opposite end thereof to define an optical path therein for optical alignment with the optical detection system, the extension tube forming a longitudinally extending composite tube; the longitudinally extending composite tube being injectable with an inert gas during use to form a melt surface immersed in the melt via the immersion end, and optically probing the immersed melt surface exposed to the inert gas via the optical path; the refractory lance assembly further comprising a shroud longitudinally receiving the longitudinally extending composite tube and defining a receiving volume therebetween, wherein a connection between the extension tube and the opposite end of the submerged tube is received within the receiving volume while the submerged end extends longitudinally therefrom for immersion into the melt, and wherein the receiving volume is capable of injecting the inert gas through the connection to reduce fluid contamination of the longitudinally extending composite tube and the submerged melt surface; The dip tube has corrosion resistance and thermal shock resistance that maintains structural integrity at temperatures of at least 1500°C, while the extension tube is defined by relatively lower corrosion resistance and thermal shock resistance. Heat resistant lance assembly.

2. the shroud coaxially houses the longitudinally extending composite tube; the shroud extends longitudinally beyond the connection toward the submerged end for at least 1 inch; or the shroud extends longitudinally beyond the connection portion toward the submerged end for at least 2 inches; 10. The heat resistant lance assembly of claim 1.

3. A heat-resistant lance tube for optically probing a melt, comprising: a dip tube having a dip end immersible in the melt, and an extension tube connected to an opposite end thereof to form a longitudinally extending composite tube and defining an optical path therein; the dip tube is at least partially fabricated from a non-porous ceramic and is substantially resistant to corrosion and thermal shock at temperatures of at least 1500°C; the dip tube is removably connected to the extension tube for replacement with at least one alternative dip tube; Heat-resistant lance tube.

4. the opposite end of the dip tube is snugly received within the connecting end of the extension tube, or vice versa; the longitudinally extending composite tube further comprising a coupler at the connection between the dip tube and the extension tube, the coupler being fabricated from one or both of borosilicate and calcium borate; the longitudinally extending composite tube further comprises a coupler at the connection between the dip tube and the extension tube, the coupler comprising one or more ferrules that receive ends of the dip tube and the extension tube, the one or more ferrules forming an insulating sheath over the connection; 4. A heat resistant lance assembly according to any one of claims 1, 2 or 3.

5. The immersion tube is a non-porous ceramic cylinder made of one of boron nitride, boron nitride containing at least 40% zirconium dioxide (zirconia), or zirconia silicate boron nitride (ZSBN) containing about 45% zirconia in a matrix of boron nitride and borosilicate glass; a ceramic cylinder coated with an insulating non-porous ceramic layer, said non-porous ceramic covering at least said immersion end; a ceramic cylinder comprising aluminum oxide (alumina) coated with an insulating non-porous ceramic layer, said non-porous ceramic covering at least said immersion end; a ceramic cylinder coated with an insulating non-porous ceramic layer made of one of boron nitride, boron nitride containing at least 40% zirconia, or ZSBN containing about 45% zirconia in a matrix of boron nitride and borosilicate glass, said insulating non-porous ceramic layer covering at least said immersion tip; or a ceramic cylinder comprising aluminum oxide (alumina) coated with an insulating non-porous ceramic layer made of one of boron nitride, boron nitride containing at least 40% zirconia, or ZSBN containing about 45% zirconia in a matrix of boron nitride and borosilicate glass, said insulating non-porous ceramic layer covering at least said immersion tip; Equipped with 5. The heat resistant lance assembly of claim 4.

6. the extension tube comprises a metal cylinder made of any one or more of molybdenum, chromium, iridium, niobium, osmium, tungsten, tantalum, or alloys thereof; or a non-porous ceramic cylinder made of either or both of Sialon and Sialon II; 5. The heat resistant lance assembly of claim 4.

7. The extension tube is reusable for two or more thermal cycles, and the dip tube is replaceable with one or more replacement dip tubes.

5. The heat resistant lance assembly of claim 4.

8. The inert gas in the containment volume is pressurized and released toward the melt to reduce oxidation of the melt surface.

5. The heat resistant lance assembly of claim 4.

9. the optical sensing system includes a laser-induced breakdown spectroscopy (LIBS) system, the optical measurements include LIBS composition measurements, and the optical path terminates in an optical window optically aligned with the LIBS system.

5. The heat resistant lance assembly of claim 4.

10. the melt comprising at least partially molten iron, steel, nickel, copper, platinum, or alloys thereof; 5. The heat resistant lance assembly of claim 4.

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