Apparatus and method for cooling molten glass in a conduit - Patent application

Abstract

The conduit is configured to transport molten glass from one molten glass processing vessel to another, and the conduit includes a cooling tube extending therethrough and configured to receive a flow of cooling fluid therethrough to thereby cool the molten glass flowing through the conduit.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority under 35 U.S.C. §19 of U.S. Provisional Patent Application No. 63 / 378,310, filed October 4, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] (Technical field) FIELD OF THE DISCLOSURE The present disclosure relates to heat extraction devices, and more particularly to conduits for extracting heat from molten glass flowing therethrough. [Background technology]

[0003] The production of glass articles, such as glass sheets, typically involves transporting molten glass from a melting furnace through multiple processing vessels to a forming device, which forms the molten glass into the desired glass article. Between the melting furnace and the forming device, the temperature of the molten glass must be tightly regulated to achieve a temperature (e.g., viscosity) suitable for forming. Cooling of the molten glass is typically achieved by radiative cooling within conduits extending between the various processing vessels. Increasing the flow rate of molten glass, e.g., to increase production volume, generally requires increasing heat loss through the conduits to achieve the required forming temperatures. This can be achieved by increasing the length or diameter of the conduits to increase surface area, using refractory materials with higher thermal conductivity, or increasing forced convection cooling applied to the exterior of the refractory material. However, the effectiveness of these approaches is limited. Furthermore, these cooling methods necessarily extract heat from the outside of the conduit to the inside, which can result in large radial temperature gradients (and therefore viscosity gradients) in the molten glass flow. Summary of the Invention [Means for solving the problem]

[0004] In a first aspect, a glass manufacturing apparatus is disclosed that includes a first molten glass processing vessel, a second molten glass processing vessel, and a conduit extending between the first and second molten glass processing vessels, the conduit defining an internal passage extending therethrough and configured to transport molten glass between the first and second molten glass processing vessels, the conduit including cooling tubes extending therethrough, at least one cooling tube defining a cooling passage isolated from the conduit internal passage by a wall of the cooling tube.

[0005] In a second aspect, the cooling pipe of the glass manufacturing apparatus of the first aspect can include a ceramic refractory lining disposed within the cooling passage.

[0006] In a third aspect, the walls of the cooling pipes of the glass manufacturing apparatus of the first or second aspect may comprise platinum.

[0007] In a fourth embodiment, the wall of the cooling tube of the glass manufacturing apparatus of the third embodiment comprises a platinum-rhodium alloy.

[0008] In a fifth aspect, the conduit of the glass manufacturing apparatus of any of the first to fourth aspects can be surrounded by a ceramic refractory material, and the cooling pipe extends outwardly from the conduit through the ceramic refractory material.

[0009] In a sixth aspect, the conduit and ceramic refractory material of the glass manufacturing apparatus of the fifth aspect can be disposed within an enclosure, and the end of the cooling pipe can be open to the atmosphere within the enclosure.

[0010] In a seventh aspect, the conduit and ceramic refractory material of the glass manufacturing apparatus of the fifth aspect can be disposed within a housing, and the cooling pipe can extend through the ceramic refractory material and the wall of the housing.

[0011] In an eighth aspect, the conduit of the glass manufacturing apparatus of any of the first to seventh aspects may have a central longitudinal axis, and the longitudinal axis of the cooling pipe may extend perpendicular to the longitudinal axis of the conduit.

[0012] In a ninth aspect, the cooling pipe of the glass manufacturing apparatus of the first aspect can include a plurality of cooling pipes.

[0013] In a tenth aspect, the glass manufacturing apparatus of claim 9, wherein the plurality of cooling pipes of the glass manufacturing apparatus of the ninth aspect can be arranged linearly and spaced apart along the longitudinal axis of the conduit.

[0014] In an eleventh aspect, the first molten glass processing vessel of the glass manufacturing apparatus of any one of the first to tenth aspects can include a fining vessel, and the second molten glass processing vessel includes a mixing device.

[0015] In a twelfth aspect, the first molten glass processing vessel of the glass manufacturing apparatus of any of the first to ninth aspects can include a mixing device, and the second molten glass processing vessel can include a delivery vessel, the delivery vessel including an outlet conduit extending from a bottom of the delivery vessel.

[0016] In a thirteenth aspect, the cooling pipe of the glass manufacturing apparatus of the first aspect can include a cooling chamber positioned within the conduit, the cooling chamber including a plurality of through-flow passages defined by the inner surfaces of a plurality of cross tubes extending through the cooling chamber, the through-flow passages configured to allow at least a portion of the molten glass conveyed through the conduit to flow through the through-flow passages.

[0017] In a fourteenth aspect, the outer surfaces of the plurality of cross tubes of the glass manufacturing apparatus of the thirteenth aspect can be coated with a refractory ceramic material.

[0018] In a fifteenth aspect, a method of producing a molten glass article is described, the method including: flowing molten glass from a first molten glass processing vessel to a second molten glass processing vessel through an internal passage defined by a conduit extending between the first and second molten glass processing vessels; and cooling the molten glass in the conduit by flowing a cooling fluid through a cooling passage of a cooling tube extending through the internal passage.

[0019] In a sixteenth aspect, the cooling fluid of the method of the fifteenth aspect can comprise an inert gas.

[0020] In a seventeenth aspect, the method of the fifteenth or sixteenth aspects may further include cooling the cooling fluid before flowing it through the cooling passages.

[0021] In an eighteenth aspect, the cooling pipe of the method of any of the first through seventeenth aspects can include a refractory ceramic lining disposed within the cooling passage.

[0022] In a nineteenth aspect, the cooling pipe of the method of any of the fifteenth to eighteenth aspects can include a cooling chamber positioned within the conduit, the cooling chamber including a plurality of cross-tubes extending therethrough, the inner surfaces of the plurality of cross-tubes defining through-flow passages, and the method further including the step of flowing at least a portion of the molten glass flowing through the internal passage of the conduit through the through-flow passages.

[0023] In a twentieth aspect, the cooling pipe of the method of any one of the first to eighteenth aspects can comprise a plurality of cooling pipes.

[0024] The foregoing summary and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and features of the embodiments disclosed herein. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. These drawings illustrate various embodiments of the present disclosure, and together with the description, serve to explain the principles and operation of the present disclosure. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of an exemplary glass manufacturing apparatus including multiple molten glass processing vessels connected by conduits; [Figure 2A] 2 is a perspective view of the exemplary conduit of FIG. 1 including at least one cooling tube extending through an interior passage of the conduit. [Figure 2B] FIG. 2B is a cross-sectional end view of the conduit of FIG. 2A. [Figure 3] FIG. 1 is a cross-sectional view of at least one cooling pipe showing the refractory lining. [Figure 4] 2 is a perspective view of the exemplary conduit of FIG. 1 including at least one cooling tube extending horizontally across the interior passage of the conduit. [Figure 5] 2 is a perspective view of the exemplary conduit of FIG. 1 including at least one cooling tube extending along the longitudinal axis of the conduit for at least a portion of the length of the conduit. [Figure 6] 2B is a cross-sectional view of the conduit of FIG. 2A, wherein the conduit is surrounded by ceramic refractory material, the conduit and ceramic refractory material are enclosed within an enclosure, and at least one cooling pipe extends from the conduit through the ceramic refractory material and is in fluid communication with a jacket volume enclosed within the enclosure. [Figure 7] 2B is a cross-sectional view of the conduit of FIG. 2A, wherein the conduit is surrounded by ceramic refractory material, the conduit and ceramic refractory material are enclosed within an enclosure, and at least one cooling tube extends from the conduit through the ceramic refractory material and the enclosure, the cooling tube being supplied with cooling fluid from a source external to the enclosure. [Figure 8] 1 is an at least partially transparent perspective view showing a cooling pipe comprising a cooling chamber positioned within a conduit, the cooling chamber comprising a plurality of through-flow passages through which molten glass can flow, the through-flow passages being defined by a plurality of cross-tubes extending through the cooling chamber, the molten glass being isolated from cooling fluid flowing within the cooling chamber by the walls of the cross-tubes; [Figure 9] 8 is a cross-sectional view of the conduit of FIG. 7 showing the flow of cooling fluid within the cooling chamber. [Figure 10]1 is a graph of modeled normalized temperature as a function of position across the width of a conduit carrying molten glass, showing that for a conduit with internal cooling tubes, the radial thermal gradient decreases after adjusting flow rate and power compared to the base case without internal cooling. [Figure 11] 8 is a graph of normalized temperature modeled as a function of position along the length of the conduit of FIG. 7 at various points around the conduit showing a reduction in radial thermal gradient after adjustments in flow rate and power compared to the base case with no internal cooling. DETAILED DESCRIPTION OF THE INVENTION

[0026] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0027] As used herein, the term "about" means that the amount, size, formulation, parameter, and other quantity and characteristic is not, and need not be, exact, but may be approximate and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding, measurement error, and the like, as well as other factors known to those of ordinary skill in the art.

[0028] Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. Further, it will be understood that the endpoints of each range are significant both in relation to the other endpoint, and independently of the other endpoint.

[0029] Directional terms used herein (e.g., up, down, right, left, front, back, top, bottom) are used solely in relation to the depicted figures and are not intended to imply absolute orientation.

[0030] Unless expressly stated otherwise, it is in no way intended that any method described herein be construed as requiring that its steps be performed in a particular order, or that any apparatus require a particular orientation. Thus, if a method claim does not recite the order in which its steps are to be followed, or if any apparatus claim does not actually recite an order or orientation for individual components, or if the claim or specification does not otherwise clearly state that the steps are to be limited to a particular order, or if no particular order or orientation for the apparatus components is recited, no order or orientation is intended to be implied in any way. This applies to all possible implicit criteria of interpretation, including matters of logic regarding the arrangement of steps, workflow, component order, or component orientation, the plain meaning derived from grammatical construction or punctuation, and the number or type of embodiments described in the specification.

[0031] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a" element includes aspects having two or more such elements unless the context clearly dictates otherwise.

[0032] As used herein, the terms "exemplary," "example," or various forms thereof mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" or "example" is not to be construed as preferred or advantageous over other aspects or designs. Moreover, examples are provided merely for clarity and understanding and are not meant to in any way restrict or limit the disclosed subject matter or relevant portions of this disclosure. It can be understood that countless additional or alternative examples of varying scope could have been presented but have been omitted for the sake of brevity.

[0033] As used herein, the terms "comprises" and "includes," and variations thereof, unless otherwise indicated, shall be construed as synonymous and open-ended. A list of elements following the transitional phrase "comprises" or "includes" is a non-exclusive list, so there may be elements other than those specifically listed in the list.

[0034] As used herein, the terms "substantial," "substantially," and variations thereof, indicate that a described characteristic is equal to or approximately equal to a value or description. For example, a "substantially planar" surface describes a surface that is planar or nearly planar. Furthermore, "substantially" is intended to indicate that two values ​​are equal or approximately equal. In some embodiments, "substantially" can mean values ​​that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0035] 1 illustrates an exemplary glass manufacturing apparatus 10. The glass manufacturing apparatus 10 comprises a glass melting furnace 12 that includes a melting vessel 14. In addition to the melting vessel 14, the glass melting furnace 12 can optionally include one or more additional components, such as heating elements (e.g., combustion burners and / or electrodes) configured to heat and convert raw material materials into molten material (hereinafter, molten glass). For example, the melting vessel 14 can be an electrically boosted melting vessel in which energy is added to the raw material materials by both combustion burners and direct heating, where an electric current is passed through the raw material materials and the electric current adds energy via Joule heating of the raw material materials.

[0036] The glass melting furnace 12 may include other thermal management devices (e.g., thermal insulation components) that reduce heat loss from the melting vessel. The glass melting furnace 12 may include electronic and / or electromechanical devices that assist in melting the raw materials into a glass melt. The glass melting furnace 12 may include support structures (e.g., support chassis, support members, etc.) or other components not shown in FIG. 1 .

[0037] The melting vessel 14 can be formed from a refractory material, such as a refractory ceramic material including alumina or zirconia, but the refractory ceramic material can alternatively or in any combination include other refractory materials such as yttrium (e.g., yttria, yttria-stabilized zirconia, yttrium phosphate), zircon (ZrSiO), or alumina-zirconia-silica, or even chromium oxide. In some examples, the glass melting vessel 14 can be constructed from refractory ceramic bricks.

[0038] The glass melting furnace 12 can be incorporated as a component of a glass manufacturing apparatus 10 configured to produce glass articles such as glass ribbons, although in other embodiments, the glass melting furnace can be incorporated into glass manufacturing apparatus configured to form other glass articles, such as, without limitation, glass rods, glass tubes, glass envelopes (e.g., glass envelopes for lighting devices such as light bulbs), glass envelopes, and glass lenses. In some examples, the glass melting furnace 12 can be incorporated into glass manufacturing apparatuses including slot draw, float bath, downdraw (e.g., fusion downdraw), updraw, press, rolling, tube draw, or any other glass manufacturing apparatus that would benefit from the present disclosure. As an example, FIG. 1 schematically illustrates the glass melting furnace 12 as a component of a fusion downdraw glass manufacturing apparatus for fusion draw forming a glass ribbon and subsequently processing it into individual glass sheets or winding the glass ribbon onto a spool for later use. As used herein, fusion draw forming involves flowing molten glass over sloping, e.g., converging, sides of a forming body, with the resulting streams of molten material meeting, or "fusing," at the bottom of the forming body to form a glass ribbon.

[0039] Glass manufacturing system 10 may optionally include upstream glass manufacturing equipment 16 positioned upstream of glass melting vessel 14. In some cases, a portion or all of upstream glass manufacturing equipment 16 may be incorporated as part of glass melting furnace 12.

[0040] As shown in FIG. 1 , the upstream glass manufacturing apparatus 16 can include a raw material storage bin 18, a raw material delivery device 20, and a motor 22 coupled to the raw material delivery device. The raw material storage bin 18 can be configured to store raw material 24, which can be fed to the melting vessel 14 via one or more feed ports, as indicated by arrow 26. The raw material 24 typically includes one or more glass-forming metal oxides and one or more modifiers. In some examples, the raw material delivery device 20 can be powered by the motor 22 to deliver a predetermined amount of raw material 24 from the raw material storage bin 18 to the melting vessel 14. In other examples, the motor 22 can power the raw material delivery device 20 to introduce the raw material 24 at a controlled rate based on a sensed level of molten glass downstream from the melting vessel 14 relative to the flow direction of the molten glass. The raw material 24 in the melting vessel 14 can then be heated to produce molten glass 28. Typically, the raw material is added to the melting vessel as particulates, such as various "sands." The raw material 24 may also include scrap glass (i.e., cullet) from previous melting and / or forming operations. A combustion burner may be used to initiate the melting process. In an electrically boosted melting process, once the combustion burner has sufficiently reduced the electrical resistance of the raw material, an electrical boost is initiated by generating an electrical potential between electrodes positioned in contact with the raw material, thereby establishing an electrical current through the raw material, which typically enters or becomes molten.

[0041] The glass manufacturing system 10 may also include downstream glass manufacturing equipment 30 positioned downstream of the glass melting furnace 12 relative to the flow direction of the molten glass 28. In some cases, a portion of the downstream glass manufacturing equipment 30 may be incorporated as part of the glass melting furnace 12. For example, a first connecting conduit 32, described below, or other portions of the downstream glass manufacturing equipment 30 may be incorporated as part of the glass melting furnace 12.

[0042] The downstream glass-making apparatus 30 can include a first conditioning chamber, such as a fining vessel 34, located downstream from the melting vessel 14 and coupled to the melting vessel 14 via the first connecting conduit 32 described above. In some examples, the molten glass 28 can be gravity-fed from the melting vessel 14 to the fining vessel 34 via the first connecting conduit 32. The first connecting conduit 32 thus provides a flow path for the molten glass 28 from the melting vessel 14 to the fining vessel 34. However, other conditioning chambers can be positioned downstream of the melting vessel 14, such as between the melting vessel 14 and the fining vessel 34. In some embodiments, a conditioning chamber can be used between the melting vessel and the fining chamber. For example, the molten glass from the primary melting vessel can be further heated in a secondary melting (conditioning) vessel or cooled in the secondary melting vessel to a temperature lower than the temperature of the molten glass in the primary melting vessel before entering the fining chamber.

[0043] Gas bubbles can be removed from the molten glass 28 by various techniques. For example, the raw material 24 may contain polyvalent compounds (i.e., fining agents), such as tin oxide, that undergo a chemical reduction reaction to release oxygen when heated. Other suitable fining agents may include, without limitation, arsenic, antimony, iron, and / or cerium, although the use of arsenic and antimony may be discouraged for environmental reasons in some applications due to their toxicity. The fining vessel 34 is heated, for example, to a temperature higher than the temperature inside the melting vessel, thereby heating the fining agents to a reaction temperature sufficient for chemical reduction. Oxygen produced by the temperature-induced chemical reduction of one or more fining agents contained within the molten glass may be entrapped in gas bubbles created during the melting process. The enlarged, more buoyant gas bubbles then rise to the free surface of the molten glass in the fining vessel and are then released from the fining vessel, for example, through a vent pipe in fluid communication with the atmosphere above the free surface.

[0044] The downstream glass-making apparatus 30 may further include another conditioning chamber, such as a mixing device 36, e.g., a stirring vessel, for mixing the molten glass flowing downstream from the fining vessel. The mixing device 36 may be used to provide a homogenous glass melt composition, thereby reducing chemical and / or thermal inhomogeneities that may otherwise be present in the molten glass exiting the fining vessel. As shown, the fining vessel 34 may be connected to the mixing device 36 by a second connecting conduit 38. Thus, the molten glass 28 may be gravity-fed from the fining vessel 34 through the second connecting conduit 38 to the mixing device 36. Typically, the molten glass in the mixing device 36 includes a free surface, with a free (e.g., gas) volume extending between the free surface and the top of the mixing device. While the mixing device 36 is shown downstream of the fining vessel 34 relative to the flow direction of the molten glass 28, in other embodiments, the mixing device 36 may be positioned upstream of the fining vessel 34. The downstream glass manufacturing equipment 30 can include multiple mixing devices, such as a mixing device upstream from the finer 34 and a mixing device downstream from the finer 34. When used, the multiple mixing devices can be of the same design or of different designs. One or more of the vessels and / or conduits disclosed herein can include stationary mixing vanes positioned therein to further promote mixing and subsequent homogenization of the molten materials.

[0045] The downstream glass manufacturing apparatus 30 may further include another conditioning chamber, such as a delivery vessel 40 located downstream from the mixing device 36. The delivery vessel 40 may function as an accumulator and / or flow controller to provide a consistent flow of molten glass 28 to a forming body 42 via an outlet conduit 44. The molten glass in the delivery vessel 40 may, in some embodiments, include a free surface, with a free volume extending upward from the free surface to the top of the delivery vessel. As shown, the mixing device 36 may be coupled to the delivery vessel 40 by a third connecting conduit 46 extending from the bottom of the delivery vessel 40, and the molten glass 28 may be gravity fed from the mixing device 36 to the delivery vessel 40 through the third connecting conduit 46.

[0046] The downstream glass manufacturing apparatus 30 can further include a forming apparatus 48 configured to form a glass article, e.g., a glass ribbon. Accordingly, the forming apparatus 48 can comprise a downdraw apparatus, such as an overflow downdraw apparatus, with an outlet conduit 44 extending from the delivery vessel 40 positioned to deliver the molten glass 28 from the delivery vessel 40 to an inlet conduit 50 of the forming body 42. In an embodiment, the outlet conduit 44 can extend into the open end of the inlet conduit 50. For example, the diameter of the distal end of the outlet conduit 44 farthest from the delivery vessel 40 can be smaller than the diameter of the open end of the inlet conduit 50, such that the distal end of the outlet conduit 44 extends into and is concentric with the inlet conduit 50, with a gap present between the distal end of the outlet conduit 44 and the open end of the inlet conduit 50. The molten glass in the gap between the distal end of the outlet conduit 44 and the open end of the inlet conduit 50 may be exposed to the ambient atmosphere.

[0047] The forming body 42 in a fusion downdraw glass manufacturing apparatus can include a trough 52 positioned on the upper surface of the forming body and opposing converging forming surfaces 54 that converge in a drawing direction 56 along a bottom edge (root) 58 of the forming body. Molten glass delivered to the trough 52 via the delivery vessel 40, outlet conduit 44, and inlet conduit 50 overflows the walls of the trough 52 and descends along the converging forming surfaces 54 as separate streams of molten glass. The separate streams of molten glass merge below along the root 58 to produce a ribbon of molten glass that is drawn from the root 58 in a drawing direction 56 by applying downward tension to the molten glass ribbon, such as by gravity and opposing counter-rotating pull rolls. The applied downward tension and the temperature of the molten glass can be used to control the dimensions of the glass ribbon as the molten glass cools and its viscosity increases. Thus, the molten glass ribbon undergoes a viscosity change from a viscous state to a viscoelastic state and then to an elastic state, acquiring mechanical properties that provide the glass ribbon 60 with stable dimensional characteristics. The molten glass ribbon 60 can then be slit to separate it into shorter lengths, such as glass sheets 62. Alternatively, the glass ribbon 60 can be wound up. The glass ribbon slitting device 64 can include a gantry (not shown) capable of vertical movement along the drawing direction at the drawing speed. The glass sheets may be removed from the glass ribbon by a robot 66. For example, the robot 66 can bend the glass ribbon at the slits to separate the glass ribbon along the slits and form the glass sheets 62.

[0048] Components of the downstream glass-making equipment 30, including any one or more of the connecting conduits 32, 38, 46, the fining vessel 34, the mixing device (e.g., stirring vessel) 36, the delivery vessel 40, the outlet conduit 44, or the inlet conduit 50, can be formed from precious metals. Suitable precious metals include platinum-group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium, and palladium, or alloys thereof. For example, the downstream components of the glass-making equipment can be formed from a platinum-rhodium alloy containing about 70 to about 90 weight percent platinum and about 10 to about 30 weight percent rhodium. Because such precious metals are quite expensive, the various vessels (e.g., conduits) are formed with thin walls and operate at high temperatures, some of which may approach the softening temperature of the metal, so that the vessels may not be able to support the weight of the molten glass contained therein unassisted at operating temperatures. Thus, a refractory ceramic material 68 (see FIGS. 6a and 6b) can be positioned around the vessel, supporting it and helping to maintain its structural integrity and regulating heat loss from the vessel. The refractory material can be formed into blocks, sheets, or plates, or can be poured as a slurry into place around the vessel and then hardened (e.g., "castable" refractory material), or both. The refractory ceramic material 68 can be arranged in multiple layers, with the refractory material in different layers having different thermal conductivities. In embodiments, different angular portions of a conduit (e.g., third conduit 46) can be wrapped with refractory material of different thermal conductivities. For example, in some embodiments, the top of the conduit can be wrapped with one or more layers of refractory material, in which case the overall thermal conductivity (e.g., average thermal conductivity) of the refractory material covering the top portion of the conduit can be different from the overall thermal conductivity of the refractory material below or to the sides of the conduit. Similarly, the thermal conductivity of the refractory material 128 may vary along the length of the conduit, so that one longitudinal portion of the conduit is configured to lose more heat than another portion of the conduit that is either upstream or downstream (relative to the direction of flow of molten glass within the conduit).

[0049] A common oxidation reaction occurring at the metal-molten glass interface in metallic (e.g., precious metal) vessels used in glass production is the conversion of negatively charged oxygen ions to molecular oxygen, which can be caused by the thermal decomposition of water and hydroxyl species in the molten glass. At the high temperatures of glass melting and delivery, a low partial pressure of hydrogen exists within the molten glass. When molten glass contained in a precious metal vessel (e.g., a conduit) comes into contact with the precious metal, the hydrogen in the molten glass rapidly permeates through the vessel wall, stripping hydrogen from the molten glass near the metal-glass interface. For every mole of hydrogen that leaves the vessel, one-half mole of oxygen is left at the metal-glass interface. Thus, as hydrogen leaves the vessel, the oxygen level, e.g., the oxygen partial pressure at the metal-glass interface, increases, potentially leading to the formation of blisters (gaseous inclusions) within the molten glass.

[0050] To mitigate gaseous inclusions, at least a portion of the downstream glass manufacturing equipment 30, which may include the vessels 34, 36, 40 and one or more of the conduits 32, 38, 46, and 44, may be enclosed or encased within an enclosure 80 designed to maintain a particular environment around the vessel. The enclosure 80 is a compact enclosure that creates a small jacket volume 82 between the enclosed equipment and the enclosure, which makes it easier to control the atmosphere within the enclosure 80, as compared to a large, room-sized enclosure, for example. This is because the volume within the enclosure 80 is smaller than the volume of a factory's open floor space, and therefore sensor readings regarding conditions inside the enclosure 80 (such as relative humidity or dew point temperature) are more likely to represent conditions on the exterior metal surfaces of the glass processing equipment.

[0051] A jacket volume 82 of the housing 80 is defined between the interior walls of the housing 80 and the exterior surfaces of one or more of the vessels 34, 36, 40 and conduits 32, 38, 46, and 44 that may be contained within the housing. The housing 80 may be leak-tight to the extent that it can be used to maintain a slight positive pressure of a low-oxygen, humid atmosphere within the jacket volume 82 that is higher than the ambient pressure conditions outside the housing 80. As shown, the housing 80 may be fabricated as one zone to contain the precious metal-containing components of the downstream glass manufacturing equipment 30. Alternatively, multiple housings 80 may be used to form multiple zones, with each housing 80 separately containing one or more of the vessels 34, 36, 40 and conduits 32, 38, 46, and 44. An advantage of using multiple housings 80 is the ability to independently control the atmosphere in specific regions of the downstream glass manufacturing equipment 30.

[0052] The enclosure 80 may further include a closed-loop control system 84 configured to control the atmosphere within the enclosure 80 to reduce or prevent oxidation reactions that may result in gaseous inclusions at the metal-glass interfaces within the vessels 34, 36, 40 and the conduits 32, 38, 46, and 44.

[0053] Specifically, the closed-loop control system 84 can control the atmosphere inside the enclosure 80 (and outside the enclosed components) to suppress undesirable oxidation reactions at the metal-glass interface by inducing hydrogen migration to the glass-metal interface. Controlling the level of hydrogen permeation into the glass-metal interface reduces the production of undesirable species such as molecular oxygen and halogens, which in turn prevents the formation of undesirable gaseous inclusions in the molten glass 28. Hydrogen permeation through the metal walls of the vessel and / or conduit can be achieved by supplying a higher hydrogen partial pressure to the exterior (non-glass-contacting) surfaces of the metal components of the downstream glass-making equipment 30 than the hydrogen partial pressure at the interior glass-metal interface. Thus, a humid, low-oxygen atmosphere can be maintained inside the enclosure 80 that can provide controlled hydrogen levels at the non-glass-contacting surfaces of the platinum-containing components of the downstream glass-making equipment 30. Accordingly, the closed-loop control system 84 can include an O and / or N make-up system 86 with an oxygen supply 88 and a nitrogen supply 90 (or a supply of another inert gas, such as argon or helium). The closed-loop control system 84 may further include a water vapor source 92 and, for example, as a carrier for the water vapor, an air source 94. The air and water vapor may be provided to the enclosure 80 through an air handler 96.

[0054] The exemplary closed-loop control system 84 may include a controller that obtains sensor readings from one or more locations inside and outside the enclosure 80. The controller processes the sensor measurements and controls various devices, such as the air handler 96 and the O2 and / or N2 replenishment system 86. In operation, the controller controls the various devices to create an atmosphere inside the enclosure 80 such that water vapor decomposition to produce hydrogen occurs at a rate equal to or greater than the rate of hydrogen permeation through the metal walls of the components 34, 36, 40, 32, 38, 46, and 44 that would occur if ambient air were present on the non-glass-contacting surfaces of the components. The presence of a higher hydrogen partial pressure prevents the formation of undesirable gaseous inclusions in the molten glass 28 by reducing undesirable species, such as molecular oxygen and / or halogens, in the molten glass. Another benefit of a higher hydrogen partial pressure is that the lower oxygen levels inside the enclosure 80 may reduce or even eliminate the oxidation rate of the platinum-containing components 34, 36, 40, 32, 38, 46, and 44.

[0055] The goal of the downstream glass-making equipment 30 is to produce and process molten glass and deliver it to a forming apparatus 48 so that it can be formed into glass products, such as glass sheets. Thus, molten glass from the glassmelting furnace 12 is processed in a fining vessel 34 to remove gaseous inclusions, homogenized in a mixing apparatus 36, and delivered to a forming apparatus 48 (e.g., a forming body 42) via a delivery vessel 40. This further requires ensuring that the molten glass is delivered to the forming apparatus at a temperature (i.e., viscosity) suitable for forming. For example, molten glass formed by a fusion downdraw process must have sufficient viscosity to flow as a ribbon from the base of the forming body and be supported by the ribbon's edges. Conduits extending between the aforementioned components (e.g., the fining vessel 34, the mixing apparatus 36, and the delivery vessel 40) can be used to reduce the average temperature of the molten glass to meet downstream processing requirements. For example, the second conduit 38 and the third connecting conduit 46 can include cooling zones, where heating or cooling methods can be used to control the rate of heat loss from the conduits and achieve a predetermined molten glass viscosity at a specified location along the flow path. Such heating and / or cooling methods can include one or more of the following: external heating coils adjacent to the conduits; direct heating of the conduits (where an electric current is established in the walls of the conduit, which heats the conduit with Joule heating, thereby regulating heat loss from the conduits); refractory insulation surrounding the conduits selected to have a predetermined thermal conductivity; and forced convection around the conduits using an air blower. A single conduit can have multiple cooling zones, where the amount of heat lost by the conduit (and thus the molten glass flowing therethrough) varies at different locations within the conduit. For example, the molten glass may be cooled in the second conduit 38 from a fining temperature, which is typically the highest system temperature and can exceed 1600°C, to a mixing temperature, which typically corresponds to a viscosity in the range of 1000 to 3000 poise. This cooling can result in a temperature reduction in the range of about 100° C. to about 300° C. The third connecting conduit 46 can further cool the molten glass from the mixing temperature to a delivery temperature and viscosity suitable for flow into the forming body (nominal viscosity of about 35 kpoise or greater).This additional cooling can result in an additional temperature reduction in the range of about 100°C to about 300°C. To achieve these cooling rates, the precious metal conduits are typically sized to have sufficient surface area to maximize heat conduction (removal) through the outer refractory structure that surrounds and supports the conduits. The combination of the geometry and thermal conductivity of the refractory, as well as the boundary conditions of the process environment, determine the magnitude of heat loss. When increasing the flow rate of molten glass to increase production or producing glasses with high cooling gradient requirements based on the viscosity point of the glass, the increased heat loss caused by the conduits, e.g., second conduit 38 and / or third connecting conduit 46, can be addressed by any combination of: (1) adding length or effective conduit diameter to the precious metal conduits; (2) using a more thermally conductive refractory supporting the conduits; and / or (3) increasing the amount of forced convection cooling applied to the exterior of the refractory.

[0056] Nevertheless, this design and scaling approach has practical limitations, namely, the expense of increased horizontal floor space in the manufacturing facility, the capital cost of additional precious metals for longer or larger diameter conduits, the limitations of known refractory thermal conductivity, and the adverse effects of excessive forced convection cooling, such as defect formation in the glass and risks to material resources. Furthermore, this combination of factors can result in cooling from the conduit walls, creating large radial temperature gradients between the molten glass in the central region of the conduit and the molten glass near the inner surface of the conduit wall(s). Such temperature gradients can make glass flow control difficult, require compensation during the forming process, and can adversely affect product properties. In more extreme cases, the edge of the cooling zone can fall below the liquidus temperature, leading to the risk of devitrification of the molten glass, especially for glass compositions with low liquidus viscosity and / or high crystal growth rates. The liquidus temperature is the temperature above which a substance becomes completely liquid and is the highest temperature at which crystals can coexist in a molten material at thermodynamic equilibrium. Such temperature deviations can therefore exacerbate the radial temperature gradient within the conduit and lead to solid inclusion defects that affect product yield. 2+Doping the glass with infrared (IR) absorbing species such as , modifies the heat transfer of the molten glass, thus exacerbating the radial effect.

[0057] In glassmaking processes where downstream chemical thermal equilibration (e.g., stirring, or sufficient time at low enough viscosity) is not possible, cooling at high viscosity carries the risk of forming heat-induced artifacts in the resulting glass product due to the nature of the melt-glass transition, where viscosity increases rapidly and local relaxation times change. This can lead to density variations in the glass product, which may manifest as "banding" defects (persistent, localized, composition-driven density differences that may exist as molten glass transitions into a solid ribbon and appear as visible defects in the ribbon). Similarly, devitrification can occur if cooling is not carefully performed, which can lead to solid inclusion defects in the glass that do not remelt or simply change composition, potentially resulting in banding defects downstream in chemical homogenization (e.g., mixing) steps.

[0058] Thus, apparatus and methods are described that employ directed cooling of the molten glass flowing within a conduit to a hotter central region. Such cooling methods can recast traditional scaling techniques to achieve higher glass flow rates per unit of precious metal without significant changes in cooling fluid (e.g., gas) flow rates. Furthermore, because this cooling is directed toward the central interior region of the conduit, these methods can directionally counteract the effects of radial temperature gradients, resulting in higher peripheral temperatures of the molten glass and reducing the risk of devitrification.

[0059] The apparatus and methods described herein can be used to redesign downstream molten glass equipment to reduce the amount of precious metals (e.g., platinum group metals) used to achieve similar flow rates (improved return on capital), or to increase the flow rate of molten glass to reduce unit costs, or both. The reduction in the effects of radial temperature gradients can be achieved by using strong IR absorbers (e.g., Fe 2+Unit costs can be improved through increased yields due to increased ability to provide products with a higher glass flow rate per capital asset (e.g., doped glass). By way of example and not limitation, aspects of the present disclosure will be described with respect to third connecting conduit 46, although it should be understood that these aspects may be applicable with respect to other vessels and / or conduits of the present disclosure, including second conduit 38.

[0060] As shown in FIGS. 2A and 2B , the third connecting conduit 46 includes a wall 100 that forms the periphery of the conduit, the wall 100 extending around the third connecting conduit 46 and defining an interior passageway 102 of the third connecting conduit 46 configured to receive a flow of molten glass. The third connecting conduit 46 further includes a longitudinal axis 104 that is centrally positioned within and extends through at least a portion of the third connecting conduit 46. That is, the third connecting conduit 46 need not be straight along its entire length. In FIGS. 2A and 2B , the third connecting conduit 46 is illustrated as having a combination of oval (or circular) and straight contours in a planar cross-section perpendicular to the longitudinal axis 104. For example, the third connecting conduit 46 can include walls including opposing circular or elliptical arcs joined by straight wall sections, thereby appearing as a flattened oval or flattened circle when viewed in cross-section. However, the third connecting conduit 46 is not limited to a flattened oval or flattened circular cross-sectional shape. For example, the third connecting conduit 46 can have a circular cross-sectional shape, an oval cross-sectional shape, a rectangular (e.g., square) cross-sectional shape, or any other cross-sectional shape suitable for conveying molten glass through the internal passage 102.

[0061] In the embodiment shown in Figures 2A and 2B, the third connecting conduit 46 comprises a first upper wall section 106a and a second lower wall section 106b opposite the first wall section 106b, the first and second wall sections 106a, 106b being joined at their ends by two opposing arc-shaped wall sections (elliptical or circular arcs), the first arc-shaped wall section 108a and the second arc-shaped wall section 108b. The first and second wall sections 106a, 106b may be substantially flat (shown as straight lines in the cross-sectional view) when viewed in cross section (see Figure 2B). The first and second arc-shaped wall sections 108a, 108b may comprise circular arcs, elongated arcs, or some other convexly curved shape (convex with respect to the central longitudinal axis 104). Thus, the third connecting conduit 46 may further comprise a major axis 110 and a minor axis 112 perpendicular to the major axis 110, where the major axis 110 represents the maximum diameter of the third connecting conduit 46 and the minor axis 112 represents the minimum diameter of the third connecting conduit 46. Each of the major axis 110 and the minor axis 112 is perpendicular to the longitudinal axis 104. The longitudinal axis 104 may intersect the intersection of the major axis 110 and the minor axis 112.

[0062] 2A , the third connecting conduit 46 further includes one or more cooling pipes 114 extending within the internal passage 102 through a central region thereof. Each of the one or more cooling pipes 114 defines a passage 116 extending therethrough that is separated from the internal passage 102 of the third connecting conduit 46 by a cooling pipe wall 118. The one or more cooling pipes 114 may extend perpendicular to the longitudinal axis 104. In embodiments, the one or more cooling pipes may intersect the longitudinal axis 104. For example, each cooling pipe 114 may extend across the entire diameter of the third connecting conduit 46, such as along the minor axis 112. In some embodiments, the one or more cooling pipes 114 may extend at a non-zero, but non-orthogonal, angle relative to the longitudinal axis 104, such as along the major axis 110.

[0063] The molten glass may flow through the internal passage 102 of the third connecting conduit 46, and a cooling fluid 120 (e.g., a gas) may flow through a cooling passage 103 defined by one or more cooling tubes 114, while separation between the molten glass 28 and the cooling fluid 120 is maintained by cooling tube walls 118. The cooling fluid 120 may include air. However, in further embodiments, the cooling fluid 120 may include primarily monatomic noble gas(es) (e.g., argon, krypton, and / or helium). In some embodiments, the cooling fluid 120 may be primarily a diatomic gas, e.g., an inert gas such as nitrogen. The cooling fluid 120 may include both a noble gas and an inert gas. The cooling fluid 120 may include hydrogen. The cooling fluid 120 may include 50% or more by volume of a noble gas and / or an inert gas. In embodiments, the cooling fluid 120 may include about 21% by volume or less of oxygen, about 15% by volume or less of oxygen, about 10% by volume or less of oxygen, about 5% by volume or less of oxygen, or about 1% by volume or less of oxygen. Limiting the amount of oxygen in the cooling fluid can minimize oxidation of the cooling tubes. However, the cooling fluid is not limited to a gas. In some embodiments, the cooling fluid 120 may be a liquid, such as water or other suitable liquid cooling medium.

[0064] Each cooling tube 114 includes a first end 122 and a second end 124 opposite the first end 122 (see FIGS. 6 and 7 ). In embodiments, the cooling tube walls 118 can be formed from the same material as the connecting conduit to which the cooling tube is joined, such as the third connecting conduit 46. For example, the third connecting conduit 46 can include platinum, such as a platinum-rhodium alloy. In such a case, the cooling tubes 114 can also include platinum, such as the same or a similar platinum-rhodium alloy. Referring to FIG. 3 , in embodiments, each cooling tube 114 can be lined with an inorganic refractory lining 126, such as an alumina or zirconia refractory lining. The refractory lining 126 can prevent a significant temperature drop in the molten glass 28 that would otherwise come into direct contact with the inner surface of the cooling tube walls 118. The presence of the refractory lining 126 avoids a reduction in the temperature of the molten glass that could result in the temperature of the molten glass dropping below the liquidus temperature of the molten glass, thereby preventing devitrification and / or compositional streaks. The combination of cooling fluid flow rate, refractory liner thickness, and material can be selected to prevent the interior cooling tube wall temperature from dropping below the liquidus temperature of the molten glass composition, thereby avoiding the possibility of devitrification or compositional streaks.

[0065] According to some embodiments, cooling fluid 120 can include the atmosphere within jacket volume 82. That is, first end 122 and second end 124 can be open to jacket volume 82, allowing the atmosphere within jacket volume 82 to flow freely through one or more cooling tubes. This flow can be thermodynamically driven, where the internal atmosphere within jacket volume 82 is heated by third connecting conduit 46 and the molten glass flowing therein, and rises through one or more cooling tubes 114. Additionally, the flow can be further driven by air handler 96.

[0066] The cooling tubes 114 can be oriented at any radial angle, e.g., any radial angle in a plane perpendicular to the longitudinal axis 104. For example, the cooling tubes 114 can extend perpendicular to the first and second wall sections 106a, 106b, as shown in FIG. 2A , or horizontally, as shown in FIG. 4 , or at any angle therebetween. Furthermore, the cooling tubes 114 can be angled in the direction of the flow of molten glass through the third connecting conduit 46 or angled against the flow of molten glass in the third connecting conduit 46. In other words, rather than being perpendicular to the longitudinal axis 104, at least one cooling tube 114 can instead form an angle, e.g., an acute angle, with the longitudinal axis 104. As shown in FIG. 5 , in some embodiments, at least a portion of at least one cooling tube 114 can be parallel to the longitudinal axis 104, e.g., extend along the longitudinal axis 104 within the third connecting conduit 46.

[0067] In embodiments, at least one cooling pipe 114 can extend beyond the wall 100 of the third connecting conduit 46. For example, as shown in FIG. 6 , one or more cooling pipes 114 can extend through the thickness of one or more layers of refractory material 128, with first and second ends 122, 124 of the cooling pipes 114 opening into the jacket volume 82 between the refractory material 128 and the housing 80. For example, in some embodiments, one or both ends 122, 124 can extend into the jacket volume 82. Referring to FIG. 7 , in other embodiments, one or more cooling pipes 114 can extend through the refractory material 128, the jacket volume 82, and the housing 80. In such embodiments, the cooling fluid 120 can be supplied to the at least one cooling pipe 114 via a cooling gas supply external to the housing 80. The cooling fluid may be supplied, for example, as an "in-house" gas stored under pressure in an on-site container (e.g., a gas cylinder, not shown) and made available to at least one cooling pipe 114 and / or other on-site equipment through appropriate coolant piping (not shown). In further embodiments, the cooling fluid 120 may be pumped through one or more cooling pipes 114. In embodiments, multiple cooling pipes may be interconnected by a common plenum that is used to supply the cooling fluid 120 to the cooling pipes.

[0068] In some embodiments, at least one cooling tube 114 can include a cooling chamber that can be configured to add additional surface area to the cooling tube and increase heat extraction from the molten glass flowing through the connecting conduit 46, particularly the central region of the internal passage 102. FIGS. 8 and 9 are perspective and cross-sectional views, respectively, of a portion of the connecting conduit 46. In this embodiment, the third connecting conduit 46 is shown as having a circular cross-sectional shape in a plane perpendicular to the longitudinal axis 104, but can have a different cross-sectional shape, such as that shown in FIGS. 6 and 7, or any other suitable cross-sectional shape. Refractory material 68 may also be present, but is not shown. In the embodiment of FIGS. 8-9, the cooling tube 114 includes a cooling chamber 200 positioned within the conduit internal passage 102, the cooling chamber 200 including a plurality of through-flow passages 202 through which the molten glass 28 flows as it flows through the internal passage 102 of the third connecting conduit 46. That is, at least a portion of the flow path of the molten glass through the third connecting conduit 46 extends through the through-flow passage 202 within the cooling chamber 200. The cooling chamber 200 is shown in FIGS. 8-9 as a hollow cylinder, defining an interior volume 204 in fluid communication with the cooling passages 103 of the cooling pipes 114, such that the cooling fluid 120 flowing through the cooling pipes 114 flows through the cooling chamber 200. Shapes other than cylindrical can be used for the cooling chamber 200. Generally, the lateral dimensions of the cooling chamber 200 will be larger than similar lateral dimensions of other portions of the cooling pipes 114. For example, as shown in the embodiment depicted in FIG. 9, the diameter of the upper portion 206 of the cooling pipe 114 above the cooling chamber 200 and / or the diameter of the lower portion 208 of the cooling pipe 114 below the cooling chamber 200 are smaller than the diameter of the cooling chamber 200. In terms of area, the cross-sectional area of ​​the upper portion 206 and / or the lower portion 208 of the cooling tube 114 may be smaller than the cross-sectional area (e.g., the largest cross-sectional area) of the cooling chamber 200, with each cross-sectional area being defined by the boundaries (walls) of each portion of the cooling tube in a respective plane parallel to the longitudinal axis 104 (e.g., a plane perpendicular to the longitudinal axis 210 extending through the cooling tube 114). The through-flow passages 202 are defined by the interior surfaces of the cross-tubes 212 positioned within and across the cooling chamber 200, and thus the through-flow passages 202 represent the internal passages of the cross-tubes 212.Thus, the outer surface of the cross tube 212 is the inner surface of the cooling chamber 200 .

[0069] In some embodiments, the cooling chamber 200 may be cylindrical and include a first cooling chamber wall 214 and a second cooling chamber wall 216 opposing the first cooling chamber wall 214, where the first cooling chamber wall 214 and the second cooling chamber wall 216 are parallel walls, e.g., planar parallel walls. However, in further embodiments, the first cooling chamber wall 214 and the second cooling chamber wall 216 may be curved walls. The first cooling chamber wall 214 and the second cooling chamber wall 216 are joined by a cylindrical cooling chamber wall 217. In the embodiment shown in FIGS. 8-9 , the cross-tube 212 is oriented parallel to the longitudinal axis 104 and extends between the first cooling chamber wall 214 and the second cooling chamber wall 216, thereby minimizing resistance to the flow of molten glass through the through-flow passage 202. However, other orientations for the cross-tube 212 are also contemplated.

[0070] In the embodiment, the cooling fluid 120 flows through the cooling pipes 114, including the cooling chamber 200, and contacts the outer surface of the cross-pipe 212 (as well as the inner surface of the cooling pipes 114, including the cooling chamber 200) that is in contact with the cooling fluid 120. Meanwhile, at least a portion of the molten glass 28 flowing through the third connecting conduit 46 flows through the through-flow passage 202 formed by the cross-pipe 212. Heat exchange between the molten glass flowing through the internal passage of the cross-pipe (i.e., the through-flow passage 202) and the cooling fluid 120 flowing through the cooling pipes 114 and the cooling chamber 200 and contacting the outer surface of the cross-pipe 212 extracts heat from the molten glass in contact with the cross-pipe 212, thereby cooling the molten glass. By locating the cooling chamber 200 in the central region of the third connecting conduit 46, the central portion of the molten glass flowing through the conduit is cooled, further reducing the radial temperature gradient of the molten glass flow. Although not shown, the interior surface of cooling chamber 200 may be lined with a refractory material as described for the interior surfaces of other portions of cooling pipe 114. In an embodiment, the exterior surface of cross pipe 212 may be lined with a refractory ceramic material 218, which may be the same as refractory lining 126. The refractory material may help to mitigate the cooling effect of the cooling chamber and prevent devitrification of the molten glass flowing through the third connecting conduit.

[0071] FIG. 10 is a graph showing modeling data for an exemplary directly heated third connecting conduit 46 extending between the mixing device 36 and the delivery vessel 40 and equipped with multiple cooling tubes under given flow characteristics. The horizontal axis represents distance along the width of the conduit, with zero representing the center of the conduit. Temperature on the vertical axis is normalized. Solid curve 300 represents temperature as a function of position across the width of the conduit (e.g., along major axis 110) transverse to the longitudinal axis of the conduit for the base case, i.e., no cooling from cooling tubes. The data shows the radial temperature gradient that exists across the width of the molten glass flow from the left edge of the molten glass flow (left metal-molten glass interface) to the right edge of the molten glass flow (right metal-molten glass interface). Dashed curve 302 represents the same configuration, but with the flow rate adjusted to obtain the same average outlet temperature as the base case. Dashed-dotted curve 304 represents similar conditions as dashed curve 302, but again with power applied to the directly heated conduit to obtain the same average outlet temperature at the conduit outlet. While radial temperature gradients are evident in all three curves, the curves including internal cooling by cooling tubes 114 (dashed curve 302 and dashed-dotted curve 304) show a reduced center temperature (temperature at zero) and therefore a reduced radial temperature gradient compared to curve 300, for the same average outlet temperature and the same or similar edge temperature (temperature at the glass-contacting surface of the side of the conduit).

[0072] Figure 11 is a graph showing (normalized) temperature as a function of length along the conduit of Figure 10. The data shows temperatures at thermocouple locations along the edges of the molten glass stream, at the side sides of the conduit (metal-molten glass interface) and at the metal-molten glass interface at the top of the conduit. As with Figure 10, Figure 11 shows data with flow rate and power adjustments. Due to scaling, the temperatures at the side edges of the molten glass stream appear slightly higher with flow rate adjustment, but the temperature at the top surface is generally significantly lower, indicating a reduced effect of radial temperature gradients.

[0073] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover all such modifications and variations provided they come within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0074] 46 Third connecting conduit 100 Wall 102 Internal passage 104 Longitudinal Axis 114 Cooling pipe 120 Cooling fluid

Claims

1. 1. A glass manufacturing apparatus comprising: a first molten glass processing vessel; a second molten glass processing vessel; a conduit extending between the first molten glass processing vessel and the second molten glass processing vessel; Equipped with the conduit defining an interior passage extending therethrough and configured to transport molten glass between the first molten glass processing vessel and the second molten glass processing vessel, the conduit including at least one cooling pipe extending through the interior passage of the conduit, the at least one cooling pipe defining a cooling passage separated from the interior passage of the conduit by a wall of the cooling pipe.

2. The glass manufacturing apparatus of claim 1 , wherein the cooling pipe comprises a ceramic refractory lining disposed within the cooling passage.

3. 3. The glass manufacturing apparatus of claim 1, wherein the wall of the cooling pipe comprises platinum.

4. The glass manufacturing apparatus of claim 3 , wherein the wall of the cooling tube comprises a platinum-rhodium alloy.

5. 5. The glass manufacturing apparatus of claim 1, wherein the conduit is surrounded by a ceramic refractory material, and the cooling pipe extends outwardly from the conduit through the ceramic refractory material.

6. 6. The glass manufacturing apparatus of claim 5, wherein the conduit and the ceramic refractory material are disposed within an enclosure, and an end of the cooling pipe is in fluid communication with the atmosphere within the enclosure.

7. 6. The glass manufacturing apparatus of claim 5, wherein the conduit and the ceramic refractory are disposed within an enclosure, and the cooling pipe extends through the ceramic refractory and a wall of the enclosure.

8. 8. The glass manufacturing apparatus of claim 1, wherein the conduit has a central longitudinal axis, and the longitudinal axis of the cooling pipe extends perpendicular to the longitudinal axis of the conduit.

9. The glass manufacturing apparatus of claim 1 , wherein the cooling pipe comprises a plurality of cooling pipes.

10. 10. The glass manufacturing apparatus of claim 9, wherein the plurality of cooling tubes are spaced apart linearly along a longitudinal axis of the conduit.

11. 11. The glass manufacturing apparatus of claim 1, wherein the first molten glass processing vessel comprises a fining vessel and the second molten glass processing vessel comprises a mixing device.

12. 10. The glass manufacturing apparatus of claim 1, wherein the first molten glass processing vessel comprises a mixing device and the second molten glass processing vessel comprises a delivery vessel comprising an outlet conduit extending from a bottom of the delivery vessel.

13. 2. The glass manufacturing apparatus of claim 1, wherein the cooling pipe comprises a cooling chamber positioned within the conduit, the cooling chamber comprising a plurality of through-flow passages defined by the inner surfaces of a plurality of cross-tubes extending therethrough, the through-flow passages configured to allow at least a portion of the molten glass conveyed through the conduit to flow therethrough.

14. 14. The glass manufacturing apparatus of claim 13, wherein the exterior surfaces of the plurality of cross tubes are coated with a refractory ceramic material.

15. 1. A method of making a molten glass article, comprising: flowing molten glass from the first molten glass processing vessel to the second molten glass processing vessel through an internal passage defined by a conduit extending between the first molten glass processing vessel and the second molten glass processing vessel; cooling the molten glass within the conduit by flowing a cooling fluid through cooling passages of a cooling tube extending through the interior passage; A method comprising:

16. The method of claim 15 , wherein the cooling fluid comprises an inert gas.

17. The method of claim 15 or 16, further comprising the step of cooling the cooling fluid before flowing it through the cooling passages.

18. 18. The method of any one of claims 15 to 17, wherein the cooling pipe comprises a refractory ceramic lining disposed within the cooling passage.

19. 19. The method of any one of claims 15 to 18, wherein the cooling pipe comprises a cooling chamber positioned within the conduit, the cooling chamber comprising a plurality of cross-tubes extending therethrough, inner surfaces of the plurality of cross-tubes defining through-flow passages, the method further comprising the step of channeling at least a portion of the molten glass flowing through the internal passage of the conduit through the through-flow passages.

20. The method of any one of claims 15 to 18, wherein the cooling tube comprises a plurality of cooling tubes.

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