MELTING FURNACE

BACKGROUND

Cross-Reference To Related Application

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 62/720416 filed on August 21, 2018, the content of which is relied upon and incorporated herein by reference in its entirety.

Field

[0002] The present disclosure generally relates to systems and methods for melting batch materials. More particularly, it relates to apparatuses and methods for determining one or more operational parameters of a system for melting batch materials, such as, for example, a length of an electrode utilized in a system for melting glass batch materials.

Technical Background

[0003] Melting furnaces can be used to melt a wide variety of batch materials, such as glass and metal batch materials, to name a few. Batch materials can be placed in a vessel having two or more electrodes and melted by applying voltage across the electrodes to drive current through the batch, thereby heating and melting the batch. The life cycle of a melting furnace can depend on electrode wear. As a point of reference, the“hot face” (or“leading face”) of the electrode is electrode end face that is nearest or in contact with batch materials within the melting furnace. The“cold face” (or“trailing face”) is opposite the hot face, and is the electrode end face furthest from the molten batch materials. A length of the electrode is the distance between the hot and cold faces. During the melting process, the hot face of the electrode can be gradually worn down due to contact with the molten batch materials, decreasing the electrode length. At some point, the electrode may become too short and may compromise safe and/or efficient operation of the furnace.

[0004] With some melting furnace configurations, the electrode is periodically advanced into the vessel to re-position the worn hot face at a desired location relative to the vessel walls, the volume of batch materials, other electrodes, etc. This electrode advancement can be done so long as a sufficient length of the electrode remains. With other melting furnace configurations, the electrode remains stationary throughout the life (or“campaign”) of the furnace. Regardless, if the electrode wears down past a predetermined point of operation, the batch materials may come into contact with furnace components that in turn may contaminate the batch. In the case of a glass melt, for instance, such contact may introduce unwanted contaminants and/or color into the glass melt or final glass product. Moreover, any holes in the electrode and/or vessel wall can provide a pathway for leakage of the batch materials, which could compromise the operational safety of the furnace. Further, desired furnace operation can be premised, at least in part, upon a relatively consistent spatial location of the hot face within the volume of batch materials and/or relative to other electrodes.

[0005] Given the above, accurately predicting a length of the electrode (as well as other end- of-life parameters of a melting furnace) can yield significant cost savings (by avoiding premature shutdown of the furnace) while also maintaining operational safety. With melting furnace configurations in which the electrode is periodically advanced, the decision on when to advance the electrode can be based upon an estimated actual length of the electrode or estimated wear rate. If the actual length or wear rate are not accurately estimated, the electrode may be advanced sooner than necessary or later than necessary; under either circumstance, inefficiencies and other concerns may arise. However, during a melt operation, it may not be possible to directly observe or measure the electrode length within the vessel. In addition, during operation, several variables can affect the electrode wear rate, such as batch material composition and/or operating temperature, which may complicate the prediction of electrode wear or make a correct prediction unlikely.

[0006] Accordingly, apparatuses and methods for monitoring operation of a melting furnace and estimating the length of electrodes in a melting furnace are disclosed herein.

SUMMARY

[0007] Some embodiments of the present disclosure relate to a method of monitoring operation of a melting furnace. The melting furnace comprises a vessel and an electrode. The electrode has a length between a leading face and a trailing face, and the leading face is open to a melting chamber of the vessel. The method comprises delivering an electromagnetic radiation input signal (e.g., light) to an optical fiber disposed within the electrode. A return signal from the optical fiber in response to the input signal is received. Length information indicative of an actual length of the electrode is generated based upon the return signal. Temperature information indicative of a temperature of a material (e.g., molten glass precursor batch material) within the melting chamber is generated based upon the return signal. In some embodiments, the return signal is backscattered light. In some embodiments, the method further comprises generating a wear profile of the electrode or an electrode bank based upon the return signals from two or more optical fibers. In some embodiments, the method further comprises generating push information based upon a wear profile history of the electrode.

[0008] Yet other embodiments of the present disclosure relate to a system for melting batch materials. The system includes a vessel, an electrode, an optical fiber, an input source, an optical collector, and an analyzer. The vessel comprises a melting chamber. The electrode comprises a length between a leading face and a trailing face. The electrode is arranged relative to the vessel such that the leading face is open to the melting chamber. The input source is optically coupled to the optical fiber and is configured to deliver an electromagnetic radiation input signal to the optical fiber. The optical collector is optically coupled to the optical fiber and is configured to receive a return signal from the optical fiber in response to the input signal. The analyzer is programed to generate length information indicative of an actual length of the electrode based upon the return signal. The analyzer is further programmed to generate temperature information indicative of a temperature of material within the melting chamber based upon the return signal. In some embodiments, the analyzer may be programmed to generate information representing a thermal profile along a length of the optical fiber. In some embodiments, at least a section of the optical fiber comprises a core material having a melting point of not less than 1100 degrees Celsius. In some embodiments, at least a section of the optical fiber comprises a single crystal sapphire core. In related embodiments, a first section of the optical fiber comprises a single crystal sapphire core and a second section of the optical fiber comprises a non-sapphire core, such as a silica core. In some embodiments, the electrode is provided as part of an electrode bank comprising a plurality of electrodes, and a plurality of the optical fibers are disposed within the electrode bank for generating information indicative of a wear profile of the electrode bank.

[0009] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0010] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic illustrating a cross-sectional view of melting furnace system including a monitoring apparatus in accordance with principles of the present disclosure;

[0012] FIG. 2A is a simplified side view of an electrode and optical fiber useful with the melting furnace system of FIG. 1, including the electrode in an initial state;

[0013] FIG. 2B is a simplified side view of the electrode and optical fiber of FIG. 2A, including the electrode worn to an intermediate state with one construction of the optical fiber;

[0014] FIG. 2C is a simplified side view of the electrode and optical fiber of FIG. 2A, including the electrode worn to an intermediate state with another construction of the optical fiber;

[0015] FIG. 2D is a simplified side view of the electrode and optical fiber of FIG. 2A, including the electrode worn to an intermediate state with another construction of the optical fiber;

[0016] FIG. 3 A is a simplified, exploded view of an electrode and optical fiber useful with the melting furnace system of FIG. 1;

[0017] FIG. 3B is a simplified side view of the electrode and optical fiber of FIG. 3 A upon final assembly; [0018] FIG. 4A is an enlarged, simplified cross-sectional view of a portion of the optical fiber of FIG. 3A;

[0019] FIG. 4B is an enlarged, simplified cross-sectional view of a portion of another optical fiber useful with the melting furnace system of FIG. 1 ;

[0020] FIGS. 5 A and 5B are schematics illustrating a portion of the melting furnace system of FIG. 1 at different stages of a batch material melting operation;

[0021] FIG. 6A is a graphical depiction of backscatter intensity as a function of optical fiber length resulting from the arrangement of FIG. 5B;

[0022] FIG. 6B is a graphical depiction of temperature as a function of optical fiber length resulting from the arrangement of FIG. 5B;

[0023] FIG. 7A is a simplified, side view of portions of another melting furnace system, including an electrode bank and a monitoring apparatus in accordance with principles of the present disclosure;

[0024] FIG. 7B is a simplified end view of a portion of the melting furnace system of FIG. 7A;

[0025] FIG. 8 is a simplified side view of the melting furnace system of FIG. 7A at a later stage of a batch material melting operation; and

[0026] FIG. 9 is a schematic illustrating a cross-sectional view of another melting furnace system including a monitoring apparatus in accordance with principles of the present disclosure.

DETAILED DESCRIPTION

[0027] Reference will now be made in detail to various embodiments of systems and methods for melting batch materials, and in particular to various embodiments of apparatuses and methods for monitoring operation of a melting furnace, for example estimating an actual length of electrodes in a vessel of the melting furnace. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0028] Embodiments of the disclosure will be discussed with reference to FIG. 1, which depicts an exemplary melting furnace system 30 for melting batch materials 32. The melting furnace 30 can include a vessel 34, at least one electrode 36, and a monitoring apparatus 38. Details on the various components are provided below. In general terms, the vessel 34 can assume various forms, and generally includes or defines side walls 40 and a floor or bottom 42 that combine to define a chamber 44. The batch materials 32 can be introduced into the chamber 44 by way of an inlet 46. The batch materials 32 can then be heated and melted in the vessel 34 by any suitable method or their combination, e.g., conventional melting techniques such as by contact with the side walls 40 and/or the floor 42, which can be heated by combustion burners (not shown) in the vessel 34 and/or by contact with the electrodes 36. The melted batch materials 32 can flow out of the vessel chamber 44 by way of an outlet 48 for further processing. The monitoring apparatus 38 operates to estimate or determine an actual length of at least one of the electrodes 36 during operation of the melting furnace 30.

[0029] The term“batch materials” and variations thereof are used herein to denote a mixture of precursor components which, upon melting, react and/or combine to form the final desired material composition. The batch materials can, for example, comprise glass precursor materials, or metal alloy precursor materials, to name a few. The batch materials may be prepared and/or mixed by any known method for combining precursor materials. For example, in certain non-limiting embodiments, the batch materials can include a dry or substantially dry mixture of precursor particles, e.g.., without any solvent or liquid. In other embodiments, the batch materials may be in the form of a slurry, for example, a mixture of precursor particles in the presence of a liquid or solvent.

[0030] According to various embodiments, the batch materials may include glass precursor materials, such as silica, alumina, and various additional oxides, such as boron, magnesium, calcium, sodium, strontium, tin, or titanium oxide. For instance, the glass batch materials may be a mixture of silica and/or alumina with one or more additional oxides. In various embodiments, the glass batch materials include from about 45 to about 95 weight percent (wt%) collectively of alumina and/or silica and from about 5 to about 55 wt% collectively of at least one oxide of boron, magnesium, calcium, sodium, strontium, tin, and/or titanium.

[0031] The batch materials 32 can be melted according to any suitable method, e.g., conventional glass and/or metal melting techniques. For example, the batch materials 32 can added to the chamber 44 and heated to a temperature ranging from about 1100 degrees Celsius (°C) to about 1700 °C, such as from about 1200 °C to about 1650 °C, from about 1250 °C to about 1600 °C, from about 1300 °C to about 1550 °C, from about 1350 °C to about 1500 °C, or from about 1400 °C to about 1450 °C, including all ranges and sub-ranges therebetween. The batch materials may, in certain embodiments, have a residence time in the vessel 32 ranging from several minutes to several hours to several days, or more, depending upon various variables, such as the operating temperature and the batch volume, and particle sizes of the constituents of the batch materials 32. For example, the residence time may range from about 30 minutes to about 3 days, from about 1 hour to about 2 days, from about 2 hours to about 1 day, from about 3 hours to about 12 hours, from about 4 hours to about 10 hours, or from about 6 hours to about 8 hours, including all ranges and sub-ranges therebetween.

[0032] In the case of glass processing, the molten glass materials can subsequently undergo various additional processing steps, including fining to remove bubbles, and stirring to homogenize the glass melt, to name a few. The molten glass can then be processed, e.g., to produce a glass ribbon, using any known method, such as fusion draw, slot draw, and float techniques. Subsequently, in non-limiting embodiments, the molten glass or glass ribbon can be formed into glass sheets, three-dimensional glass articles, cut, polished, and/or otherwise processed. Features of the present disclosure can be utilized with other molten glass-based materials, such as glass ceramics.

[0033] The vessel 34 can be formed of any insulating or heat-resistant material suitable for use in a desired melting process, for example, refractory materials such as zircon, zirconia, alumina, magnesium oxide, silicon carbide, silicon nitride, and silicon oxynitride, precious metals such as platinum and platinum alloys, and combinations thereof. According to various embodiments, portions (e.g., the side walls 38, the floor 40, etc.) can include an outer layer with an interior lining of heat-resistant material such as a refractory material or precious metal. The vessel 34 can have any suitable shape or size for the desired application and can, in certain embodiments, have, for example, a circular, oval, square or polygonal cross-section. The dimensions of the vessel 34, including the length, height, width, and depth, to name a few, can vary depending upon the desired application. Dimensions can be selected as appropriate for a particular process or system. While FIG. 1 illustrates the vessel 34 as having the inlet 46 and the outlet 48, which can be suitable for continuous processing, it is to be understand that other vessel configurations can be used, which may or may not include an inlet and/or outlet, and which can be used for batch or semi-batch processing.

[0034] FIG. 1 illustrates that in some embodiments, the electrodes 36 are connected within and extend though a corresponding one of the side walls 40. As a point of reference, FIG. 1 identifies a first one of the electrodes 36a assembled to a first one of the side walls 40a. In particular, the first electrode 36a is disposed in an opening 50 through a thickness of the first side wall 40a, and is arranged to be exposed to or in contact with the batch materials 32 contained in the chamber 44. For example, the first electrode 36a is illustrated as extending through the opening 50, projecting beyond an inner surface 52 of the first side wall 40a (and thus into the chamber 44). In other embodiments, one or more of the electrodes 36 can be arranged to be flush with or inside of the corresponding side wall inner surface in a manner that permits the electrode 36 to directly interface with the batch materials 32 contained in the chamber 44. For example, the first electrode 36a can alternatively be arranged to terminate at the inner surface 52 of the first side wall 40a; alternatively, the first electrode 36a can be arranged to terminate within a thickness of the first side wall 40a and directly exposed to the batch materials 32 contained in the chamber 44 via the opening 50 at the inner surface 52. Regardless, upon final assembly to the vessel 34, each of the electrodes 36 can be viewed or considered as defining a leading face (or“hot face”) 60 opposite a trailing face (or“cold face”) 62. The leading face 60 is the electrode end face nearest or in contact with the batch materials 32, and is open to the chamber 44 (e.g., the leading face 60 is located within the chamber 44, or is within a thickness of the side wall 40 and is exposed to the batch materials 32 within the chamber 44 via the opening 50). The trailing face 62 is the electrode end face farthest away from the batch materials 32, and is not within or open to the chamber 44. A length 66 of the electrode 36 is the distance between the corresponding leading and trailing faces 60, 62.

[0035] In some embodiments, assembly of each of the electrodes 36 to the vessel 34 (e.g., to a corresponding one of the side walls 40) is such that the electrodes 36 can be advanced relative to the corresponding side wall 40 (and thus relative to the chamber 44). For example, in some non-limiting embodiments, mounting of the first electrode 36a to the first side wall 40a is such that the first electrode 36a can be slid or pushed relative to the first side wall 40a, re-positioning the leading face 60 relative to the chamber 44. During operation, the first electrode 36a will experience wear over time, primarily at the leading face 60, resulting in a decrease in the length 66. In other words, the leading face 60 will physically erode toward the trailing face 62. When the first electrode 36a is stationary or fixed relative to the first side wall 40a, a physical location of the leading face 60 relative to the first side wall 40a will thus change as the first electrode 36a experiences wear. Under these circumstances and with optional embodiments in which the first electrode 36a is slidably mounted to the first wall 40a, the first electrode 36a can be periodically advanced toward the chamber 44 (i.e., moved in the rightward direct relative to the orientation of FIG. 1) to reposition the now-worn leading face 60 at a desired location relative to the inner surface 52. In other embodiments, one or more (including all) of the electrodes 36 can be permanently fixed to the corresponding vessel structure (e.g., one of the side walls 40).

[0036] While FIG. 1 illustrates three electrodes 36, it is to be understood that any number of electrodes may be used as required or desired for a particular application. In some embodiments, pairs of the electrodes can be aligned with one another across a dimension of the vessel 34. For example, in the non-limiting example of FIG. 1, a second electrode 36b is aligned with the first electrode 36a; electrical conduction can be across the first and second electrodes 36a, 36b and thus through the batch materials 32. Other electrode arrangements are also acceptable. While FIG. 1 illustrates the electrodes 36 attached within the side walls 40, it is to be understood that the electrodes 36 can be configured within the vessel 34 in any orientation and can be attached to any wall of the vessel 34, such as the floor 42 or roof of the vessel 34.

[0037] The electrodes 36 can have any dimension and/or shape suitable for operation in a melting furnace. For instance, in some embodiments, the electrodes 36 can be shaped as rods or blocks. The electrodes 36 can have any suitable cross-sectional shape, such as square, circular, or any other regular or irregular shape. Moreover, the initial length of the electrodes 36 can vary depending on the application and/or size of the vessel 34. In some non-limiting embodiments, the electrodes 36 can have an initial length ranging from about 10 centimeters (cm) to about 200 cm, such as from about 20 cm to about 175 cm, from about 30 cm to about 150 cm, from about 40 cm to about 125 cm, from about 50 cm to about 100 cm, or from about 60 cm to about 75 cm, including all ranges and subranges therebetween.

[0038] The electrodes 36 can comprise any material suitable for the desired melting application. For example, the electrode material can be selected such that the normal wear or erosion of the electrode 36 during operation has little or no detrimental impact on the batch composition and/or final product. In various non-limiting embodiments, such as glass melting operations, one or more of the electrodes 36 can include one or more oxides or other materials that can be present in the final glass composition. For example, the electrode 36 can include an oxide already present in the batch materials 32 (e.g., nominally increasing the amount of the oxide in the final product) or an oxide not present in the batch materials 32 (e.g. introducing small or trace amounts of the oxide into the final composition). By way of non-limiting example, one or more of the electrodes 36 can include stannic tin oxide, molybdenum oxide, zirconium oxide, tungsten, molybdenum zirconium oxide, platinum and other noble metals, graphite, silicon carbide, and other suitable materials and alloys thereof.

[0039] The monitoring apparatus 38 can assume various forms, and generally includes an optical fiber 80 and a control unit 82 including an input source 84, an optical collector 86, and an analyzer 88. In general terms, the optical fiber 80 is associated with (e.g., embedded within, coupled to, etc.) one of the electrodes 36 (e.g., the first electrode 36a in the example of FIG. 1). The input source 84 is optically coupled to the optical fiber 80 and is configured to deliver an electromagnetic radiation input signal (e.g., light) to the optical fiber 80. The optical collector 86 is optically coupled to the optical fiber 80 and is configured to receive a return signal (e.g., returned light) in response to the input signal. The analyzer 88 is a computer-like device programmed to determine an actual length of the electrode 36 with which the optical fiber 80 is associated (e.g., the first electrode 36a in the example of FIG. 1) based upon the return signal, and to generate temperature information indicative of a temperature of the batch materials 32 within the chamber 44 based upon the return signal. While FIG. 1 illustrates one optical fiber 80, in other embodiments two or more optical fibers can be provided. For example, and as described in greater detail below, an optical fiber can be provided for two or more (including all) of the electrodes 36. Alternatively or in addition, two or more optical fibers 80 can be associated with one of the electrodes 36. [0040] The optical fiber 80 can assume various forms appropriate for carrying or transmitting electromagnetic radiation, or light, signals. In general terms, the optical fiber 80 can include a core and a cladding layer selected for total internal reflection due to the difference in the refractive index between the two. The optical fiber 80 can be a single-mode fiber or a multi- mode fiber. In addition, the optical fiber 80 can be provided as part of a fiber optic cable that includes two or more optical fibers.

[0041] In some embodiments, a portion or an entirety of the optical fiber 80 can include a core formed of a material appropriate for transmitting light at wavelengths expected to be utilized during operation of the monitoring apparatus 38. In related embodiments, a portion or an entirety of a core of the optical fiber 80 is formed of a material appropriate for transmitting light at the expected wavelengths, with the core and/or other components of the optical fiber 80 having a melting point greater than about 1100 °C, optionally greater than about 1850 °C. For example, in some non-limiting embodiments, a portion or an entirety of a core of the optical fiber 80 is a sapphire-based material, such as single crystal sapphire. In other embodiments, a portion or an entirety of a core of the optical fiber 80 can comprise pure silica or silica doped with at least one dopant (e.g., Ge, Cl, Bo, Fl, Fe, P, Al, and/or Ti). Other optical fiber core materials are also envisioned as known in the art. In some example embodiments, a core of the optical fiber 80 can comprise a material having a melting point of not greater than about 1100 °C, and is covered with an exterior shield or cladding that limits or prevents erosion or wear of the core at expected temperatures and operating conditions. By way of non-limiting example, a core of the optical fiber 80 can be covered (e.g., electroplated) with material resistant to dissolving or melting in the molten batch materials 32 (e.g., will not dissolve in a molten tin-based, glass batch material) such as an alumina tube and/or a platinum foil.

[0042] The optional high melting point properties of the optical fiber 80 (e.g., an optical fiber core material such as single crystal sapphire or other material having a melting point greater than an expected temperature of the molten batch materials 32) have surprisingly been found to facilitate long term operation of the optical fiber 80 in generating useful electrode 36 length and batch material 32 temperature information. For example, and with reference to FIG. 2 A, the optical fiber 80 terminates at a first end 90. An arrangement of the first end 90 relative to the electrode 36 can be selected based upon an initial or starting length of the electrode 36. As a point of reference, it will be recalled that during batch material melting operations, the leading face 60 of the electrode 36 erodes over time. Thus, the length of the electrode 36 decreases over time. FIG. 2 A represents the electrode 36 as initially provided (i.e., in an initial state prior to use of the electrode 36 in a batch material melting operation) and as having an initial length 100. Upon final assembly of the optical fiber 80 to the electrode 36 in the initial state, the first end 90 can be proximate (e.g., aligned with, slightly recessed from, or slightly projecting beyond) the leading face 60. With optional embodiments in which the optical fiber 80 (or at least a portion of the optical fiber 80 otherwise including the first end 90) is configured to not erode (or erode to a lesser extent) under the same conditions that otherwise cause the electrode 36 to wear, a relationship of the first end 90 relative to the leading face 60 will change over time. FIG. 2B represents this possible construction, depicting that at a later point in time during a melting operation, the electrode 36 has eroded in the presence of the molten batch materials 32 and now has an intermediate length 102 (that is otherwise less than the initial length 100 (FIG. 2A)), whereas the optical fiber 80 has experienced minimal, if any, wear. The first end 90 is now beyond the leading face 60, and is exposed the batch materials 32. By optionally employing a core material for the optical fiber 80 that does not wear or erode at the same rate (if at all) as the electrode 36, the optical fiber 80 can provide information indicative of a temperature of the batch materials 32 in addition to information indicative of an actual length of the electrode 36 as described in greater detail below.

[0043] In other embodiments, the optical fiber 80 can experience some wear under the same conditions that otherwise cause the electrode 36 to wear, but at a lesser rate or extent as compared to wearing of the electrode 36. For example, FIG. 2C represents this possible construction, depicting that at a later point in time during a melting operation (i.e., a later point in time from the initial state of FIG. 2A), the electrode 36 has eroded to the intermediate length 102 as described above, and the optical fiber 80 has also eroded from the initial state of FIG. 2A. However, the wear rate of the optical fiber 80 is less than the wear rate of the electrode 36, and the first end 90 of the optical fiber 80 is beyond the leading face 60 of the electrode 36.

[0044] In yet other embodiments, the optical fiber 80 wears at approximately the same rate as the electrode 36. For example, FIG. 2D represents this possible construction, depicting that at a later point in time during a melting operation (i.e., a later point in time from the initial state of FIG. 2 A), the electrode 36 has eroded to the intermediate length 102 as described above, and the optical fiber 80 has eroded from the initial state of FIG. 2 A at the same rate as the electrode 36. The first end 90 of the optical fiber 80 is aligned with the leading face 60 of the electrode 36.

[0045] Returning to FIG. 2A, other relationships between the first end 90 of the optical fiber 80 and the leading face 60 of the electrode 36 (in the initial state) are also acceptable. For example, the first end 90 can be located within a thickness of the electrode 36, recessed or “behind” the leading face 60 at a predetermined position (e.g., corresponding with a minimum length of the electrode 36). Once the leading face 60 has eroded to the first end 90, the optical fiber 80 may then generate distinctive information (e.g., noticeably different from information generated prior to the leading face 60“reaching” the first end 90) that is readily interpreted as the electrode 36 having worn to the predetermined position. Then, a direct measure of the rate of continued electrode 36 wear can be monitored or determined as function of measured, continued wearing of the optical fiber 80. In yet other embodiments, the first end 90 can be located beyond the leading face 60 (in the initial state of the electrode 36).

[0046] In some embodiments, at least a portion of the optical fiber 80 can include a coating or cladding over the core material. For example, a coating or cladding can be provided along at least that portion of the optical fiber 80 located within the electrode 36 (and possibly projecting beyond the leading face 60 of the electrode 36). In some embodiments, a portion of the optical fiber 80 can include a sapphire-based core (e.g., single crystal sapphire) and a coating or cladding layer of non-sapphire-based material, for example a metallic material (e.g., platinum) or non-metallic material (e.g., silica). In some embodiments, the optional coating or cladding layer can comprise pure silica or silica doped with at least one dopant (e.g., index- decreasing dopants such as F and/or B, or index-increasing dopants such as Ge, P, Al, and/or Ti). In other embodiments, the coating or cladding layer can be omitted.

[0047] A diameter of the optical fiber 80, and particular that portion of the optical fiber 80 disposed within the electrode 36, can vary depending upon operating parameters. In some embodiments, the diameter of the optical fiber 80 at least along that portion of the optical fiber 80 disposed within the electrode 36 can range, for example, from about 10 microns to about 1000 microns, such as from about 25 microns to about 500 microns, from about 50 microns to about 125 microns, including all ranges and subranges therebetween. In other embodiments, a diameter of the optical fiber 80, including that portion of the optical fiber 80 disposed within the electrode 36, can have a diameter greater than 1000 microns. The optical fiber 80 can be assembled or mounted to the electrode 36 in various fashions, for example by forming a bore in the electrode 36 having a diameter commensurate with a diameter of the optical fiber 80.

[0048] In some embodiments, at least a portion of the optical fiber 80 can include gratings or other light scattering mechanisms in or on a core of the optical fiber 80. With some examples, the grating can be Fiber Bragg Gratings (FBG), which are by definition within the fiber. As a point of reference, when light is coupled out of an optical fiber and into another optical device, precise spatial alignment can be important to avoid major optical losses. If filtering processes could be performed in the fiber, unnecessary losses can be avoided. FBGs are periodic modulations of the index of refraction inside the core of an optical fiber. In a basic configuration, FBGs act as a filter, allowing all light to pass through except for a selected wavelength. This particular wavelength is reflected back down the optical fiber and is referred to as the Bragg wavelength. It is a function of the periodic physical spacing of changes in refractive index, as well as the effective refractive index of the gratings in the core. Other grating formats or light scattering mechanisms as understood by one of ordinary skill are also acceptable. For example, gratings or other light scattering mechanisms can be provided along at least that portion of the optical fiber 80 located within the electrode 36 (and possibly projecting beyond the leading face 60 of the electrode 36). In yet other embodiments, tracks or other micro structures can be created in or on the optical fiber 80 (e.g., parallel, laser-written tracks) that generate stress in the optical fiber 80 for guiding light. In other embodiments, the gratings or other light scattering mechanisms can be omitted.

[0049] In some embodiments, the optical fiber 80 can comprise two or more sections having different constructions, such as a first section 110 and a second section 112 as illustrated in FIG. 3A and 3B. In general terms, the first section 110 defines the first end 90 described above, and a second end 114 opposite the first end 90; similarly, the second section 112 defines a first end 116 opposite a second end 118. The first section 110 is optically coupled or joined to the second section 112, and is configured (e.g., sized and shaped) for assembly to or within the electrode 36 such that the first end 90 is closer to or more proximate the leading face 60 as compared to the second end 114. The second section 112 has a core material or other property differing from that of the first section 110, and extends from the first section 110 to the control unit 80 (FIG. 1). A length of the first section 110, and an arrangement of the first section 1 10 relative to the electrode 36, can be selected based upon an initial or starting length of the electrode 36. FIGS. 3A and 3B represent the electrode 36 as initially provided (i.e., prior to use of the electrode 36 in a batch material melting operation) and as having the initial length 100. A length 120 of the first section 110 of the optical fiber 80 can be selected to locate the leading end 90 at a desired position relative to the leading face 60 as described above, and to locate the second end 114 proximate (e.g., aligned with, slightly recessed from, or slightly projecting beyond) the trailing face 62 of the electrode 36 as shown in FIG. 3B. Thus, in some example, the length 120 of the first section 110 can approximate (e.g., can be equal to, slightly greater than, slightly lesser than, etc.) the initial length 100 of the electrode 36. In some embodiments, a diameter of the first section 110 is substantially the same as a diameter of the second section 112 (i.e., within 5% of truly identical diameters). In other embodiments, the first and second sections 110, 112 can have differing diameters. For example, a diameter of the second section 112 can be greater than a diameter of the first section 110. In some non limiting embodiments, the first section 110 (otherwise located within the electrode 36) can have a diameter on the order of 125 micrometers (“microns) as otherwise typically employed in optical fiber telecommunication applications, whereas the second section 112 has a diameter on the order of 500 - 1000 microns. With these and similar embodiments, the larger diameter second section 112 can exhibit increase strength and stability (as compared to the first section 1 10) and can thus be well suited for extension to the control unit 82 (FIG. 1). Other diameters are also envisioned. In yet other embodiments, the optical fiber 80 can comprise three or more sections.

[0050] The second section 112 extends from the first section 110 and is located outside of a useful region of the electrode 36. As a point of reference, oftentimes the useful life or campaign of the melting furnace 30 (FIG. 1) ends before an entirety of the electrode 36 is consumed. For example, while the electrode 36 can be periodically advanced relative to the vessel 34 (FIG. 1) during the campaign as mentioned above, it is often the case that operation of the melting furnace 30 will be discontinued (e.g., for safety reasons) once the electrode 36 has worn to a minimum length. FIGS. 3A and 3B generally identify one example of a possible minimum length 130 assigned to the electrode 36. Stated otherwise, once the leading face 60 has eroded to a hypothetical end point 132, the electrode 36 may no longer be considered viable and operation of the melting furnace 30 is discontinued. As the electrode 36 wears from the initial length 100 to the minimum length 130, it may be beneficial to estimate or determine the actual length and/or wear rate of the electrode 36 at any point in time. Thus, relative to the initial state of the electrode 36, a useful region 134 of the electrode 36 is that region between the hypothetical end point 132 and the leading face 36. With these explanations in mind, the first and second sections 110, 112 can be sized such that the first section 110 is located along the useful region 134, and the second section 112 is located outside of (e.g., does not extend along) the useful region 134. In some embodiments, the first end 116 of the second section 112 can be located within a thickness of the electrode 36, between the trailing face 62 and the hypothetical end point 132. In other embodiments, the first end 116 of the second section 112 can be located outside of the electrode 36 (e.g., the second end 114 of the first section 112 is beyond the trailing face 62). Regardless, in some embodiments a length of the second section 112 is greater than a length of the first section 110.

[0051] With the above optional constructions, a core of the first section 110 can be formed of a material that differs from a material of a core of the second section 112. For example, the core of the first section 110 can be a sapphire-based material (e.g., single crystal sapphire), whereas the core of the second section 112 can be a non-sapphire-based material (e.g., silica, doped silica, other light transmitting material having a melting point less than the melting point of sapphire or single crystal sapphire, etc.). In related embodiments, the first section 110 can include a component not provided with, or differing from, the second section 112. For example, the first section 110 can include a cladding or protective layer over the core, and the second section 112 does not include this same cladding or protective layer. Regardless of an exact format, the first section 110 is thus configured, in some non-limiting embodiments, to maintain its structural integrity under conditions otherwise causing wearing of the electrode 36, whereas the second section 112 may or may not erode under these same conditions. In these and other examples, by forming the first and second sections 110, 112 of differing materials and/or of differing structures, an overall cost of the optical fiber 80 can be lesser as compared to a configuration in which an entirety of the optical fiber 80 has a singular construction (e.g., an entirety of the optical fiber 80 has a single crystal sapphire core). In other examples, the optional gratings or other light scattering mechanisms described above can be provided with the first section 110 and omitted from the second section 112.

[0052] The first and second sections 110, 112 can be optically coupled to one another in various fashions. FIG. 4A illustrates that in some embodiments, a joint 132 is formed between the first and second sections 110, 112, with the second end 114 of the first section 110 abutting the first end 116 of the second section 112. A mechanical fixture can be employed to align and retain the second end 114 of the first section 110 and the first end 116 of the second section 112 relative to one another. For example, one segment of the fixture can have a v-shaped groove that cradles the two optical fiber sections 110, 112, and a second segment that maintains pressure against the fiber sections 110, 112 and keeps them in the groove. One non-limiting example of a useful mechanical fixture is a UniCam® connector available from Corning Inc. of Corning, NY. In other embodiments, the second end 114 of the first section 110 is placed within a first connector suited for a configuration of the first section 1 10, and the first end 116 of the second section 112 is placed within a second connector suited for a configuration of the second section 1 12; the first and second connectors are then physically mated to one another. Other optical coupling formats are also acceptable. Moreover, FIG. 4B illustrates another example optical coupling between the first section 110 and an alternative second section 112’. As shown, a diameter of the second section 112’ can taper at a first end 116’ thereof to a diameter approximating that of the first section 110.

[0053] Returning to FIG. 1, the input source 84, the optical collector 86, and the analyzer 88 are optionally provided as the single control unit 82 configured to transmit light to the optical fiber 80, receive or collect light returned from the optical fiber 80, and analyze the returned light, respectively. In some embodiments, the control unit 82 operates to determine length and other information based on backscattering. In general terms, the input source 84 (e.g., a swept laser, coherent light source, broadband light source, etc.) injects a signal into the optical fiber 80 and the optical collector 86 extracts, from the same end of the optical fiber 80, light that is scattered (Rayleigh backscatter) or reflected from points along the optical fiber 80. The scattered or reflected light that is gathered back is used by the analyzer 88 to characterize the optical fiber 80. The magnitude and/or phase of the returned signal is measured and can be integrated as a function of time, and can be plotted as a function of a length of the optical fiber 80. Rayleigh scattering is when light interacts elastically with a particle or other inhomogeneity much smaller than its wavelength and changes directions. When the light is scattered such that the light propagates in the reverse direction, this is referred to as Rayleigh backscatter. Because the light is elastically interacting with particles, it does not change energy and therefore does not change its wavelength to facilitate interferometric sensing. For example, the control unit 82 can be or operate as an optical time domain reflectometer, an optical frequency domain reflectometer, etc. In some non-limiting embodiments, the control unit 82 can be an Optical Backscatter Reflectometer™ available from Luna Innovations Inc. of Blacksburg, VA, an ultra-high resolution reflectometry device with backscatter-level sensitivity for interrogating components. With these and related embodiments, the control unit uses swept-wavelength coherent interferometry to measure minute reflections in the optical fiber 80 as a function of length. This technique can measure (e.g., via a tunable laser source and polarized detectors) a full scalar response of the optical fiber 80, including both phase and amplitude information. Backscatter can be measured with a spatial resolution of, for example, 10 microns, and the location of events along the optical fiber 80 can be determined at this resolution. A section of the optical fiber 80, and its associated backscatter, can be used to determine spatially resolved temperature with a typical resolution of about one millimeter to several centimeters. The temperature variations along the optical fiber 80 can be used to determine electrode wear or actual length, as well as other temperature-related features of interest, such as a temperature of the batch materials 32. Other control unit or optical system configurations are also acceptable, generally operating to interpret a signal from a beam sent into the optical fiber 80 and any light that is returned or emitted from the optical fiber 80, for example due to the optical fiber 80 attaining an elevated temperature and emitting radiation.

[0054] With reference to the simplified top view of FIG. 5 A, some methods of the present disclosure can include initially arranging the melting furnace 30 as shown. In the initial arrangement of FIG. 5 A, the electrode 36 has not yet been activated to perform a melting operation, and thus has the initial length 100. The optical fiber 80 is disposed within the electrode 36, with the first end 90 aligned with the leading face 60 and thus at known or pre- determined distance from the trailing face 62 (it being recalled that other relationships between the first end 90 of the optical fiber 80 and the leading face 60 of the electrode 36 are also acceptable). The melting furnace 30 is then operated to melt the batch materials 32, such as by energizing the electrode 36. With these operations, the electrode 36 will wear over time, experiencing erosion at the leading face 60. FIG. 5B represents the melting furnace 30 at a later point in time; a comparison of FIGS. 5 A and 5B illustrates that the leading face 60 of the electrode 36 has eroded. Thus, at the point in time of FIG. 5B, the electrode 60 has an actual length 140 that is less than the initial length 100 (FIG. 5A). The optical fiber 80 does not wear at the same rate as the electrode 36, if at all. Thus, at the point in time of FIG. 5B, the first end 90 of the optical fiber 80 is now beyond the leading face 60 and is exposed to the batch materials 32. As a point of reference, while the arrangement of FIG. 5B generally reflects that the optical fiber 80 has not experienced any erosion (as compared to FIG. 5 A), in other embodiments, the optical fiber 80 may experience some erosion but at a lesser rate as compared to the electrode 36 (e.g., as explained above with respect to FIG. 2C); in yet other embodiments, the optical fiber 80 may wear at the same rate as the electrode 36 (e.g., as explained above with respect to FIG. 2D).

[0055] At various times during operation of the melting furnace 30 to melt the batch materials 32, the monitoring apparatus 38 (FIG. 1) is operated to generate information relating, for example, to the electrode 36 (e.g., the monitoring apparatus 38 can continually operate throughout the melting operations, can be operated at predetermined times, can be prompted to operate by a user, etc.). For example, the monitoring apparatus can be operated at the point in time of FIG. 5B. An electromagnetic radiation input signal is delivered to the optical fiber 80, a return signal in response to the input signal is received or collected, and the collected signal is analyzed. FIGS. 6 A and 6B are representations of possible return signals or information resulting from the electrode 36/optical fiber 80 relationship of FIG. 5B. FIG. 6 A is a backscatter signal or intensity 150 along the length of the optical fiber 80. The backscatter signal 150 has a relatively uniform appearance along a first segment 152 that can otherwise be interpreted or designated as corresponding to a region at which the optical fiber 80 is within the electrode 36. A first discernible deviation 154 in the backscatter signal 150 can be interpreted or designated as corresponding with the region of the optical fiber 80 that is not otherwise within or encompassed by the electrode 36 (i.e., the first deviation 154 initiates at a point corresponding with a location of the leading face 60). In other words, the electrode 36 affects backscattering along the first segment 152, and this same affect is not present along the first deviation 154. A second discernible deviation 156 can be interpreted or designated as corresponding to the first end 90 of the optical fiber 80 (e.g., a peak in the backscatter signal 150 due to the reflection from the fiber/batch material interface at the end of the optical fiber 80). The actual length 140 of the electrode 36 can be determined or estimated from these (or other) return interpretations. For example, under circumstances where the first end 90 was aligned with the leading face 60 in the initial state of the electrode 36 (i.e., FIG. 5A), the distance or length between initiation of the first deviation 154 and the second deviation 156 can be determined or estimated as being the decrease in electrode length. For example, if the initial length 100 of the electrode 36 was 60 cm and the length between initiation of the first deviation 154 and the second deviation 156 is 2 cm, it can be determined or estimated that the actual length 140 of the electrode 36 (again, at the point in time of FIG. 5B) is 58 cm (i.e., 60 cm - 2 cm) . As a point of reference, zone 158 identified in FIG. 6 A can be a result of instrument noise. Other algorithms for determining or estimating the actual length 140 of the electrode 36 from the return signal information are also acceptable. Additionally or alternatively, once an initial length is captured, the rate of change in length of the fiber zones (e.g., location of where initiation of the first deviation 154 starts along the fiber length, or distance of where the second deviation 156 starts, etc.) can be used to determine the rate at which the length of the electrode 36 is decreasing as a function of time, or as a function of other process variables such as temperature of the batch materials 32, etc.

[0056] In addition to determining or estimating the actual length 140 of the electrode 36 at any point in time, the return signal can be utilized to generate information indicative of a temperature (or temperature profile) of the batch materials 32. For example, and with continued reference to FIG. 5B, FIG. 6B is a plot 160 of change in temperature (relative to a baseline temperature outside of the vessel 34) along the length of the optical fiber 80 as generated by an optical backscatter reflectometer based upon a received backscattering return signal as is known in the art. From the discussions above, it will be recalled that first end 90 of the optical fiber 80 is beyond the electrode 36 and directly within the batch materials 32. Thus, temperature information along the plot 160 at a region 162 corresponding with the first end 90 (e.g., designated to be directly within the batch materials 32) is indicative of a temperature of the batch materials 32 (at least in an area of the vessel 34 otherwise corresponding with a location of the optical fiber 80). Alternatively or in addition, the temperature profile of other equipment can be estimated. For example, the temperature-related information embodied by the return signal from the optical fiber 80 can be reviewed to evaluate a temperature profile of the vessel side wall 40 in which the electrode 36 is disposed.

[0057] Other optical-based control units can be used with the optical fiber 80 to generate information implicating the actual length 140 of the electrode 36 that may or may not be premised upon backscatter. In other embodiments, the optical fiber 80 can be configured to melt or erode at approximately the same rate as the electrode 36, and from the optical return signal, the actual length 140 of the electrode 36 can be estimated or determined from the determined length (or change in length) of the optical fiber 80. Alternatively, the optical fiber 80 can be configured to wear at different rates over time. For example, the optical fiber 80 can be configured to initially wear back into the electrode 36 (e.g., the optical fiber 80 initially wears at a wear rate greater than the wear rate of the electrode 36) and then is stabilized at a certain distance inside the electrode 36 from the leading face 60, and then continues to wear at the same rate as the electrode 36, maintaining that distance from the leading face 60. In these and other optional embodiments of the present disclosure, a temperature or temperature profile of the batch materials 32 may not be determined.

[0058] Portions of another example of a melting furnace 200 in accordance with principles of the present disclosure are shown in FIG. 7A and 7B, and includes the vessel 34 as described above, an electrode bank 202 and a monitoring apparatus 204 (referenced generally). The electrode bank 202 can be of a type conventionally employed for large scale melting operations (e.g., melting of glass precursor batch materials), and generally includes two or more of the electrodes 36 described above arranged in an array. A leading face 206 of the electrode bank 202 is collectively defined by the leading face of each of the individual electrodes 36. The electrodes 36 of the electrode bank 202 can be commonly powered or energized by a single source (not shown) in some embodiments. Further, the electrode bank 202 is mounted relative to the side wall 40 of the vessel 34 such that all of the electrodes 36 of the electrode bank 202 are collectively movable relative to the side wall 40. In other words, to effect a change in a location of the leading face 206 relative to the side wall 40, the entire electrode bank 202 is moved as a single unit.

[0059] The monitoring apparatus 204 can be akin to the monitoring apparatus 38 (FIG. 1) described above, and includes two or more of the optical fibers 80 and the control unit 82 as described above. The optical fibers 80 are disposed within the electrode bank 202 at various, spaced apart locations. For example, FIGS. 7A and 7B reflect that a first optical fiber 80a can be horizontally aligned with and vertically spaced above a second optical fiber 80b; FIG. 7B reflects that a third optical fiber 80c can be vertically aligned with and horizontally spaced from the first optical fiber 80a. In some embodiments, an optical fiber 80 is provided for each of the electrodes 36 within the electrode bank 202. In other embodiments, an optical fiber 80 is provided for less than all of the electrodes within the electrode bank 202. An arrangement and location of the optical fibers 80 relative to the electrode bank 202 can assume a number of different formats. In some embodiments, respective ones of the fibers 80 can be located at positions where wearing of the electrode bank 202 is expected to be more prevalent. Regardless of how the optical fibers 80 are arranged within the electrode bank 202, each of the optical fibers 80 can be connected the control unit 82 (for example via an optical switch main frame (not shown) as known in the art), or two or more control units 82 can be provided that interface with selected ones of the optical fibers 80.

[0060] During operation of the melting furnace 200 in performing a melting operation, the monitoring apparatus 204 is periodically or continuously operated to evaluate the electrode bank 202. For example, FIG. 8 is a representation of the electrode bank 202 at a later point in time, and generally reflects wearing or erosion along the leading face 206. While the optical fibers 80 are shown as not having eroded or worn to the same extent as the electrodes 36 (if at all), in other embodiments of the present disclosure, one or more (including all) of the optical fibers 80 can be formatted to erode or melt commensurate with erosion of the electrode 36 in which the optical fiber 80 is disposed. Regardless, with operation of the monitoring apparatus 204, an electromagnetic radiation (light) input signal is delivered to each of the optical fibers 80 (e.g., simultaneously or in series), and the corresponding return signal from each of the optical fibers 80 is collected and analyzed. The electrode length information (or other electrode-related information of interest such as temperature or change in temperature) associated with each of the optical fibers 80 is then collectively reviewed to generate a wear profile of the leading face 206 of the electrode bank 202. The so-generated wear profile can provide a meaningful understanding of an actual wear contour along the leading face 206. For example, with the arrangement of FIG. 8, information from each of the vertically spaced apart optical fibers 80 can result in a wear profile indicating that vertically, or from top-to-bottom, portions of the leading face 206 have eroded differently. Depending upon the number and locations of the optical fibers 80 relative to the electrode bank 202, the generated wear profile can indicate that horizontally, or from left-to-right, portions of the leading face 206 have eroded differently. Thus, depending upon the number and locations of the optical fibers 80 relative to the electrode bank 202, the wear profile provided by some embodiments of the present disclosure can be two-dimensional or three-dimensional. In related embodiments, the relative rate of change of all of the array of optical fibers 80 can be used to determine the relative rate of change of the electrodes 36 of the electrode bank 202. The relative rate of change of an electrode length, once measured for a set of variables, such as batch material content and process thermal set-up, can then be applied in the case of fiber equipment failure to continue to predict the position of the leading face 206.

[0061] The electrode bank wear profile can optionally be utilized for various operational evaluations and alterations, and in some embodiments the evaluations are performed automatically by software or other programming. For example, based upon of the electrode bank wear profile, an informed decision can be made as to whether or not the electrode bank 202 should be moved or pushed relative to the side wall 40 (e.g., under circumstances where at least a portion of the leading face 206 has significantly eroded), and if so, a desired movement distance. In related embodiments, a series or history of electrode bank wear profiles can be reviewed or monitored over time to increase the accuracy of electrode bank 202 movement timing and distance. With these and related embodiments, the likelihood of possible seepage of the batch materials around the electrode bank 202 due to under pushing or movement of the electrode bank 202 is decreased, as is the likelihood of electrode“slabbing” due to over pushing. The electrode bank wear profiles can be used to more accurately project a useful life of the melting furnace 200, and can provide data useful, for example, for troubleshooting zirconia or tin defect upsets against electrode temperature changes.

[0062] While some embodiments have been described as including the optical fiber 80 embedded within the electrode 36, in other embodiments of the present disclosure, the monitoring apparatuses of the present disclosure can provide temperature profile information for other components of the melting furnace apart from the electrodes. For example, another melting furnace system 30’ in accordance with principles of the present disclosure is shown in FIG. 9 and includes the optical fiber 80 of the monitoring apparatus 38 embedded within a thickness of the first side wall 40a (and not otherwise directly associated with any of the electrodes 36). The monitoring apparatus 38 can be operated as described above to provide information indicative of a temperature profile of the first side wall 40a throughout an operational campaign.

[0063] The melting furnaces, monitoring apparatuses, and methods of the present disclosure provide a marked improvement over previous designs. Reliable length and optionally leading (or“hot”) face wear profile information for an electrode or electrode bank can be obtained and reviewed during a batch material melting operation. Further, batch material temperature information can also be provided. The optical fiber-based monitoring apparatuses of the present disclosure, such as those incorporating a sapphire (e.g., single crystal sapphire) core, are well-suited for providing length-resolved temperature data that in turn can be used to analyze electrode wear.

[0064] Various modifications and variations can be made to the embodiments described herein without departing from the scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modifications and variations come within the scope of the appended claims and their equivalents.