CN110803857A

CN110803857A - Apparatus and method for making glass

Info

Publication number: CN110803857A
Application number: CN201911192726.9A
Authority: CN
Inventors: 安格利 G·德; M·A·德拉米勒; M·H·戈勒尔; S·克里西那莫西; G·K·施文克
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2013-10-18
Filing date: 2014-10-14
Publication date: 2020-02-18
Anticipated expiration: 2034-10-14
Also published as: JP2016533313A; CN105829253B; KR102288421B1; WO2015057646A1; JP6754469B2; CN105829253A; KR102230177B1; KR20160074536A; TWI633072B; KR20210032544A; JP2019163205A; JP6533221B2; TW201516015A; CN110803857B

Abstract

A molten glass delivery apparatus is disclosed comprising a fining vessel comprising a wall, wherein the wall thickness of the fining vessel varies circumferentially. In some embodiments, the upper portion of the fining vessel that is in contact with the gaseous atmosphere within the fining vessel is thinner than the remaining portion of the fining vessel that is in contact with the molten glass. A method of fining molten glass is also disclosed.

Description

Apparatus and method for making glass

The patent application of the invention is a divisional application of an invention patent application with the international application number of PCT/US2014/060398, the international application date of 2014 is 10-month and 14-day, the application number of the invention entering the Chinese national stage is 201480069200.0, and the invention name is 'equipment and a method for manufacturing glass'.

Priority

This application is based on the priority of U.S. provisional application serial No. 61/892624, filed 2013, 10, 18, 35 u.s.c. § 119, which is incorporated herein by reference in its entirety.

Background

FIELD

The present invention relates generally to an apparatus for making glass, and more particularly, to a molten glass delivery apparatus comprising a vessel comprising a wall having a thickness that varies circumferentially around a perimeter of the vessel.

Technical Field

Melting raw materials to form a molten material (hereinafter referred to as molten glass) requires the use of combustion gases and/or electrical energy during the melting process. The raw material may then be conditioned and transported from the furnace to the forming apparatus. In some processes, molten glass is delivered to a forming apparatus by a precious metal delivery apparatus comprising various processing equipment. To ensure a controlled temperature, certain components of the delivery apparatus may be directly heated by generating an electrical current in those components. The electric current heats the assembly, which in turn heats the molten glass therein. Different components of the delivery device have different energy requirements. The most power demanding component of the delivery apparatus is perhaps the fining vessel in which the molten glass is conditioned to remove gases generated in the melting process.

The fining vessel is maintained at a very high temperature in order to effectively remove bubbles after the melting process and to ensure the breakdown of any solid particles escaping from the furnace. The bubbles rise faster at lower viscosities and the solid inclusions decompose faster at higher temperatures. The top of the clarifier has an air gap. Unfortunately, noble metals (e.g., platinum and/or rhodium) can oxidize in the presence of oxygen, and the rate at which oxidation occurs increases with temperature and oxygen content. Oxidation of the noble metal results in thinning of the metal. Oxidation is generally more severe at the top of the fining vessel for at least two reasons: 1) an air gap exists above the surface of the molten glass; and 2) the temperature at the top of the fining vessel is highest. For some glasses, the temperature at the top of the fining vessel may exceed 1700 ℃. Typically, the temperature at the top of the fining vessel may be 20 ℃ higher on average than the temperature of the molten glass remaining in the lower portion of the fining vessel. Because higher temperatures at the top of the fining vessel can lead to corrosion failure of the fining vessel, it is desirable to reduce the top temperature within the fining vessel.

Summary of The Invention

The ability of the molten glass manufacturing process to produce thin glass sheets with surface qualities beyond those expected makes these glass sheets ideal for the manufacture of visual display products such as televisions, cell phones, computer monitors, and the like. In a typical fusion process, raw materials (formed into batches) are melted in a refractory ceramic melting furnace to produce molten glass. The molten glass is then delivered to the forming body by a delivery apparatus. The forming body includes a groove formed in an upper surface thereof, and an outer converging forming surface. Molten glass is received from a delivery device by a trough from which it overflows and flows downwardly in separate streams over converging forming surfaces. The separate streams combine where the converging forming surfaces meet to form a single glass ribbon that is cut into individual glass sheets once it has cooled to an elastic solid.

Although the furnace and the forming body are mostly made of refractory ceramic materials, the delivery device for delivering the molten glass to the forming body is generally made using high temperature metals, in particular oxidation resistant high temperature metals. Suitable metals may be selected, for example, from the platinum group metals, i.e., platinum, iridium, rhodium, palladium, osmium, and ruthenium. Alloys of the above platinum group metals may also be used. For example, molten glass delivery apparatus are often made from platinum or alloys of platinum (e.g., platinum-rhodium alloys) because platinum or alloys of platinum (e.g., platinum-rhodium alloys) are more easily physically processed than other platinum group metals.

When molten glass is delivered by a delivery apparatus, it can be conditioned by passing the molten glass through a conditioning vessel, such as a fining vessel, where the degassing process occurs. Various gases are formed during the melting process. If these gases remain in the molten glass, bubbles may be generated in the finished glass article, such as a glass sheet obtained by the fusion process. To eliminate bubbles in the glass, the temperature of the molten glass in the fining vessel is increased to a temperature above the melting temperature. Multivalent compounds contained in the batch materials and present in the molten glass release oxygen during temperature elevation and help sweep gases formed during the melting process of the molten glass. These gases are released into the fining vessel discharge space above the free surface of the molten glass. In some cases, such as the production of glass sheets for the display industry, the temperature in the fining vessel can exceed 1650 ℃, even 1700 ℃, and approach the melting temperature of the fining vessel walls.

One method of increasing the temperature in a fining vessel is to generate an electrical current in the fining vessel, where the temperature is increased by the resistance of the metal walls of the vessel. Such direct heating may be referred to as joule heating. To achieve this heating, electrodes (also called flanges) are connected to the fining vessel and act as the inflow and outflow points for the electrical current.

Monitoring of the fining vessel temperature at various locations within the fining vessel may be accomplished by embedding thermocouples in the refractory and insulating material surrounding the fining vessel. This monitored data shows an increase in temperature in the fining vessel at the gaseous atmosphere above the free surface of the molten glass in contact with the walls of the fining vessel. This may be attributed to a reduction in the thermal conductivity of the gaseous atmosphere within the fining vessel relative to the thermal conductivity of the molten glass contained within lower portions of the fining vessel. A cross-section of a scrapped fining vessel shows excessive oxidation of the upper portion of the fining vessel not in contact with the molten glass, particularly where the flange meets the fining vessel wall. This oxidation occurs due to the high temperature of the metal in the presence of oxygen. Unfortunately, it is difficult to completely eliminate oxygen from the environment surrounding the fining vessel. In addition, this oxidation can gradually thin the vessel wall metal in regions of the vessel where molten glass does not flow, eventually leading to failure of the vessel wall. Accordingly, embodiments disclosed herein relate to controlling the flow of electrical current through a fining vessel wall to reduce the temperature of the portion of the wall where the wall is in contact with the gaseous atmosphere within the fining vessel and where the molten glass does not flow.

In one aspect, a delivery apparatus for molten glass is disclosed, comprising: a fining vessel configured as a tube comprising a wall, the wall of the tube comprising a metal selected from the group consisting of platinum, rhodium, palladium, iridium, ruthenium, osmium, and alloys thereof; a plurality of flanges surrounding the tube and configured to conduct electrical current through the wall, the plurality of flanges comprising platinum, rhodium, palladium, iridium, ruthenium, osmium, and alloys thereof. At least a portion of the wall between at least two consecutive flanges of the plurality of flanges comprises a circumferentially varying thickness. The term "two continuous flanges" is intended to mean that the molten glass passes through the two continuous flanges in sequence, without an intervening flange between the two continuous flanges, in the direction of flow of the molten glass.

The at least a portion of the wall may include a first wall portion and a second wall portion, and a thickness of the first wall portion may be less than a thickness of the second wall portion at a cross section of the at least a portion of the wall. The thickness of the first wall portion may be substantially uniform and the thickness of the second wall portion may be substantially uniform. The first wall portion is located at the top of the fining vessel and the second wall portion is located at the bottom of the fining vessel, with the second wall portion being below the first wall portion.

The molten glass delivery apparatus can also include a third wall portion located between the first wall portion and the second wall portion. The thickness of the third wall part at said cross section may be greater than the thickness of the second wall part.

The second wall portion may be made to comprise a plurality of layers. For example, the second wall portion may comprise a laminated structure comprising a plurality of metal plates.

In another embodiment, the at least a portion of the fining vessel wall can comprise a first wall portion and a second wall portion, wherein the first wall portion has a thickness greater than a thickness of the second wall portion. The first wall portion is located at the top of the fining vessel and the at least a portion of the wall may be located adjacent to one of the two continuous flanges.

The thickness of the first and/or second wall portion may be substantially uniform.

In some embodiments, when the first wall portion is thicker than the second wall portion, the length of the first wall portion may be no greater than about 16 cm.

The first wall portion may comprise a plurality of metal layers when the first wall portion is thicker than the second wall portion. According to some aspects of this embodiment, the first wall portion abuts one of the two continuous flanges. In other aspects, a flange may be attached to an upper surface of the first wall portion, such as to a central portion of the first wall portion, such that the first wall portion extends outwardly from the flange parallel to the longitudinal axis of the fining vessel. In one example, the first section has a length of 16cm along the longitudinal axis of the fining vessel, and the flange is connected to the first section at a midpoint of the 16cm length. It should be apparent from the above description that the length may be other than 16cm, for example less than 16cm, with the flange being connected to the first wall portion at a midpoint of its length.

The at least a portion of the wall may include a first length portion, a second length portion spaced apart from the first length portion, and a third length portion located between the first and second length portions. The thickness of the first length portion may vary circumferentially, the thickness of the second length portion may vary circumferentially, and the thickness of the third length portion may be substantially constant. Additionally, the first and second length portions may each include a first wall portion and a second wall portion, and the first wall portions of the first and second length portions may have a thickness greater than the thickness of the second wall portions of the first and second length portions. The first wall portions of the first and second length portions may be located at the top of the fining vessel.

Each of the first and second length portions may be located adjacent to one of the two continuous flanges such that each of the first and second length portions abuts a respective one of the two continuous flanges.

The molten glass delivery apparatus may also include a fourth length between adjacent flanges, the fourth length including a first wall portion and a second wall portion, the first wall portion of the fourth length being located at the top of the fining vessel. The thickness of the first wall portion of the fourth length portion may be greater than the thickness of the second wall portion of the fourth length portion.

In another embodiment, a method of forming glass is disclosed that includes melting batch materials in a furnace; flowing molten glass from a furnace through a metal fining vessel such that the molten glass includes a free surface within the fining vessel and an atmosphere is between the fining vessel and the free surface, the fining vessel including a wall including a first wall portion including a first thickness and a second wall portion including a second thickness such that, in cross-section, the first thickness is different than the second thickness. The flow of the molten glass is controlled so that the stream of the molten glass does not flow over the surface of the upper wall portion. The first wall portion is therefore located at the top of the fining vessel and the second wall portion is located at the bottom of the fining vessel.

The first thickness may be less than the second thickness, or the first thickness may be greater than the second thickness.

In some embodiments, the fining vessel may comprise a third wall portion located between the first wall portion and the second wall portion, the third wall portion comprising a third thickness greater than the first thickness and the second thickness at the cross-section. The level of molten glass in the fining vessel can be controlled such that the free surface intersects the third wall portion.

The temperature of the first wall portion may be, for example, at least 5 degrees celsius (° c) lower than the temperature of the second wall portion.

Additional features and advantages of the invention 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 invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description describe embodiments of the invention and are intended to provide an overview or framework for understanding the nature and character of the embodiments as they are claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operations of these embodiments.

Brief description of the drawings

FIG. 1 is a front view of an exemplary fusion downdraw glass manufacturing apparatus including a fining vessel according to embodiments described herein;

FIG. 2 is a perspective view of the fining vessel of FIG. 1;

FIG. 3 is a cross-sectional view of a prior art fining vessel including a wall with a circumferentially uniform thickness;

FIG. 4 is a photograph of a corrosion failure of a clarifying vessel wall;

FIG. 5 is a cross-sectional view of a fining vessel according to embodiments described herein, wherein the wall thickness of the fining vessel wall varies circumferentially;

FIG. 6 is an electrical schematic illustrating the effect depicted in FIG. 5;

FIG. 7 is a cross-sectional view of another embodiment of a fining vessel as described herein, wherein the wall thickness of the fining vessel varies circumferentially such that the upper wall portion is thinner than the lower wall portion, and the lower wall portion comprises multiple layers;

FIG. 8 is a cross-sectional view of another embodiment of a fining vessel as described herein, wherein the wall thickness of the fining vessel varies circumferentially with an intermediate wall portion disposed between the upper and lower wall portions;

FIG. 9 is a side view of a fining vessel including both thin portions and thick portions in the upper portion of the fining vessel;

FIG. 10 is a cross-sectional view of the fining vessel of FIG. 9, wherein the cross-section shown is taken at a thick portion of the upper wall portion;

FIG. 11 is a cross-sectional view of the fining vessel of FIG. 9, wherein the cross-section shown is taken at a thin portion of the upper wall portion;

FIG. 12 is an electrical schematic illustrating the effect of including a thin upper wall portion and a thick upper wall portion in a fining vessel;

FIG. 13 is a side view of a fining vessel including a thin upper wall portion located between two thick upper wall portions;

FIG. 14 is a side view of a fining vessel illustrating an upper wall portion, a lower wall portion, the upper and lower wall portions being positioned between two consecutive flanges, wherein the upper wall portion is thinner than the lower wall portion and the electrodes interfacing with the flanges extend upwardly from near the upper portion of the top of the fining vessel;

FIG. 15 is a cross-sectional view of a fining vessel according to an embodiment in which the flange electrode extends downward from a position on the flange closest to the bottom of the flange;

FIG. 16 is a cross-sectional view of a fining vessel according to an embodiment in which the flange electrode extends downward from a position on the flange closest to the bottom of the flange;

FIG. 17 is a graph of modeled and actual temperature as a function of length along a fining vessel with the temperature at the top of the fining vessel being substantially higher than the temperature of other portions of the fining vessel having a wall with a substantially uniform thickness circumferentially at a cross-section of the fining vessel;

FIG. 18 is a side view of a fining vessel modeled by the curves of FIG. 17;

FIG. 19 is a graph modeling current density as a function of length along the fining vessel of FIGS. 17 and 18;

FIG. 20 is a graph illustrating modeled temperature as a function of length along a fining vessel, the fining vessel including an upper wall portion, a lower wall portion, and the upper wall portion having a thickness that is less than a thickness of the lower wall portion; and

FIG. 21 is a graph showing the modeled current density of the fining vessel of FIG. 20 as a function of length.

Detailed Description

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "flange" includes aspects having two or more such flanges, unless the context clearly indicates otherwise.

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 aspect includes from the one particular value and/or 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. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. When a range is expressed as "between" one value and another value, the one value and the other value denote the endpoints of the range, and are included in the range.

As used herein, the terms "having" and "including" are open-ended terms and do not exclude the presence of other properties, features, attributes or elements, unless specifically stated otherwise.

As used herein, the term "circumferentially" is generally construed to refer to angular position about the perimeter of a cross-section and is not limited to a circular cross-section, and thus, the phrase that the thickness varies circumferentially means that the thickness of a cross-section of an article (e.g., fining vessel) wall varies about the variation of angular position of the fining vessel relative to the longitudinal axis and is not limited to circular (cylindrical) fining vessels.

As used herein, an angle subtended by an arc, line or other curve refers to the angle formed by two rays passing through the ends of the arc.

As used herein, the term "vessel" should be understood to include a trough, conduit, pipe, or other structure through which molten glass may be contained and flowed.

In the exemplary glass forming apparatus 10 shown in FIG. 1, at a first temperature T₁The batch material, represented by arrow 12, is then melted in furnace 14 to form molten glass 16. T is₁Depending on the specific glass composition, but for glasses suitable for use as substrates for liquid crystal displays, T₁May exceed 1500 deg.c. Molten glass flows from melting furnace 14 through connecting conduit 18 to fining vessel 20. The glass flows from the fining vessel 20 through connecting conduit 24 to the stirring vessel 22, where the molten glass is mixed and homogenized in the stirring vessel 22 and flows from the stirring vessel 22 through connecting conduit 26 to the delivery vessel 28 and then through the outlet conduit 30 to the forming body inlet conduit 32. The molten glass may then be directed from the inlet conduit 32 to the forming body 34. In the case of the fusion downdraw process shown in FIG. 1, the molten glass delivered to forming body 34 flows over converging forming surfaces 36, where the separate streams join or fuse at the location where the converging forming surfaces meet, referred to as root 38, to form glass ribbon 40. The glass ribbon may then be cooled and separated to form individual glass sheets.

The molten glass is heated above T in fining vessel 20₁Second temperature T₂. Heating of fining vessel 20 may be accomplished by, for example, establishing an electrical potential across at least a portion of the length of the fining vessel using flange 42 associated with the fining vessel. Which in turn connects flange 42 to a suitable power source (not shown in the figures). Fining vessel 20 includes at least two flanges 42. The electrical potential is responsible for generating an electrical current that heats the fining vessel. Additional flanges may be attached to connecting conduit 18 to similarly direct heat the connecting conduit to heat the molten glass flowing therethrough to a fining temperature T₂. But T₁Up to 1500 ℃, and in some cases even higher, T₂Comparable T₁At least 100 ℃ higher. Relatively higher temperature T₂The viscosity of the molten glass is reduced, allowing bubbles in the molten material to be more easily eliminated from the molten glass. In addition, higher temperatures may release oxygen contained in fining agents (e.g., multivalent oxide materials) that may pass through the batch materials into the molten glass. The released oxygen is in the molten glassForming bubbles that can act as nucleation sites for other gases. That is, the gas dissolved in the molten glass migrates into the oxygen bubbles, making the bubbles larger. The increase in buoyancy caused by the enlargement of the bubbles accelerates the discharge of the bubbles from the molten glass through the free surface of the molten glass. In addition, as the bubbles rise through the molten glass, some localized mechanical agitation also occurs, which further promotes the expulsion of gas.

Although the furnace 14 typically comprises a refractory ceramic material (e.g., ceramic bricks or monolithic ceramic blocks), many of the downstream delivery equipment responsible for delivering the molten glass from the furnace to the forming body are typically formed from electrically conductive metals. These components include connecting

conduits

18, 24, 30; a fining vessel 20; a stirring vessel 22; a delivery container 28; an outlet conduit 30 and an inlet 32.

As noted above, molten glass is at elevated temperatures, and thus, delivery apparatus components require "high temperature" materials, such as materials capable of withstanding temperatures in excess of at least 1500 ℃ for extended periods of time. In addition, the material should be resistant to oxidation, which can be accelerated by high temperatures in the presence of oxygen. In addition, the molten glass can be quite corrosive, and therefore the material should be relatively resistant to attack by the glass, which can result in contamination of the finished glass article by the container material. Metals including the platinum group metals of the periodic table-platinum, rhodium, iridium, palladium, ruthenium, osmium, and alloys thereof-are particularly useful for this purpose, and because platinum is easier to process than other platinum group metals, many high temperature processes use containers of platinum or platinum alloys. One common platinum alloy is a platinum-rhodium alloy. However, because such precious metals are expensive, all effort has been made to minimize the size of these vessels to reduce the weight of the metal used.

To extract the most gas from the molten glass in the fining vessel, the molten glass is raised to a fining temperature T₂. Heating of the molten glass may be initiated within connecting conduit 18 between melting furnace 14 and fining vessel 20 such that the molten glass is at or near the fining temperature as the molten glass enters the fining vessel. Although accessible from the exterior of the connecting conduit 18The heating coil performs direct heating, and more efficient heating can be achieved by the direct heating method summarized above. For a directly heated fining vessel, the current may be Alternating Current (AC) or Direct Current (DC). Direct heating of the connecting conduit and fining vessel may be provided and therefore the connecting conduit and fining vessel may include flange 42.

To ensure a substantially uniform current flow in the fining vessel, care is taken in the design of flange 42 and its attachment to the fining vessel. Nevertheless, hot spots within the fining vessel are detected within the upper portion of the fining vessel wall.

FIG. 2 illustrates a perspective view of at least a portion 43 of fining vessel 20, fining vessel 20 having a nominally cylindrical cross-sectional shape and length L, and including several flanges 42 connected to and in electrical contact with the fining vessel as shown, flanges 42 being shown in FIG. 2 as the endpoints of the at least a portion. As used herein, the term "cross-sectional shape" (or simply "cross-section") refers to the shape of the fining vessel's outer wall 44 when cut by a plane 46 perpendicular to the longitudinal axis 48 of the fining vessel, unless otherwise specified. Although the following description assumes a cylindrical cross-sectional shape, it will be appreciated that other geometric cross-sectional shapes may be employed, such as elliptical, oval, or "racetrack" (e.g., oblong/circular) shapes comprising two opposing planar wall portions connected by a curved wall portion, wherein the shape has a dimension in one direction, e.g., width, that is greater than its dimension in an orthogonal direction, e.g., height. Electrode 49 is in electrical contact with flange 42 and serves to connect the flange to a power source via a cable, bus bar or other electrical conductor.

Fig. 3 shows a cross-section of an exemplary fining vessel including a longitudinally closed wall 44, with the wall 44 enclosing a longitudinally extending volume therein. The cross-section of fig. 3 is shown containing molten glass 16 having free surface 50, free surface 50 being in contact with gaseous atmosphere 52 thereabove. Wall 44 includes an inner surface 54 and an outer surface 56, wherein inner surface 54 faces the internal volume of the fining vessel enclosed by the wall and outer surface 56 is exposed to the ambient environment outside of the fining vessel. More specifically, FIG. 3 shows the relative thickness of wall 44 extending around the circumference of the fining vessel between the inner and outer surfaces, which is substantially constant in the illustrated fining vessel. That is, the thickness "t" of the cross-section of the fining vessel wall shown in FIG. 3 is substantially constant at any angular position around the circumference of the fining vessel, varying within conventional manufacturing tolerances only at joints and/or weld points.

To reduce heat loss from fining vessel 20, the fining vessel may be surrounded by one or more layers of refractory and insulating material (not shown in the figures), and a thermocouple embedded within the refractory sheath may be used to monitor the temperature of the fining vessel at or near the thermocouple. As described above, such monitoring shows that the temperature of the fining vessel wall is higher where the inner surface 54 of the wall is in contact with the contained gaseous atmosphere 52, rather than the portion of the wall in contact with the molten glass. A cross-section of a scrapped fining vessel shows an increase in the degree of oxidative corrosion of the metal in the portion of the fining vessel where the inner surface does not contact the molten glass flowing through the fining vessel. This localized corrosion can prematurely thin the wall. Thinning of the wall increases the current density in this localized portion of the wall, which further increases the temperature. Thus, once the wall begins to thin, corrosion (e.g., oxidation) can become a runaway process that continues to accelerate until a fining vessel wall failure occurs and the fining vessel must be scrapped. A photograph of such corrosion failure is shown in fig. 4, where the region 58 shown includes a breach of the clarifying vessel wall. In addition, cracks created by corrosion may extend around the fining vessel, and in some extreme cases, the cracks may meet and completely separate one region of the fining vessel from another.

It should be appreciated that the corrosion process described above is typically a local event and depends at least on the local current density and oxygen concentration. That is, this corrosion does not occur uniformly over the entire wall surface, even when only the portion of the fining vessel wall that is in contact with the gaseous atmosphere above the free surface of the molten glass is considered. Moreover, since the local based oxygen concentration may be difficult to control, one idea is to control the current density and thus the temperature of the fining vessel wall.

Therefore, fining vessel 20 of the embodiments disclosed herein are configured with a cross-sectional shape such that the wall thickness varies circumferentially around the fining vessel in at least a portion of the fining vessel, and in some embodiments, the wall thickness may vary throughout the length of the fining vessel. That is, when a cross-section of the fining vessel is viewed, the thickness of the fining vessel wall may vary angularly as the interface is viewed by an observer around the perimeter of the cross-section. In other embodiments, the wall thickness may vary at one cross-section of the fining vessel and not at another cross-section. FIG. 5 shows a cross-section of an embodiment of fining vessel 20, wherein the fining vessel comprises an upper or first wall portion 44a forming a first circular arc and a lower or second wall portion 44b forming a second circular arc, wherein the first and second wall portions make up the entirety of fining vessel wall 44. The first and second wall portions each have a wall thickness t_aAnd t_bAnd according to the present embodiment, t is t when a cross section of the fining vessel is observed_bGreater than t_a. That is, the wall thickness t of the upper wall portion 44a at the cross section_aIs smaller than the wall thickness t of the lower or second wall portion 44b in cross section_b. As shown in FIG. 5, the free surface 50 of the molten glass 16 intersects the second wall portion 44b so that the molten glass 16 does not flow through the upper wall portion 44a of the fining vessel 20. The first arc of the upper wall portion may subtend an angle θ in the range of about 10 degrees to about 180 degrees, and thus in some embodiments the upper wall portion may comprise the entire upper half of the fining vessel, or in other embodiments the upper wall portion may comprise only a portion of the upper half of the vessel. The secondary angle phi subtended by the second arc of the lower or second wall portion may be in the range of about 180 degrees to about 350 degrees.

In the embodiment of fig. 5, the thicker lower second wall portion 44b may have a lower electrical resistance in the fining vessel than the electrical resistance of the upper portion. As a result, weaker currents in the first wall portion may generate lower temperatures in the first wall portion when compared to currents in the second wall portion. This can be better understood with the aid of fig. 6.

FIG. 6 illustrates the first resistance element RE_aAnd a second resistance element RE_bSchematic diagram of the electrical appliance. Resistance element RE_aComprising a length L_aCross-sectional area A_aAnd resistivity ρ_a. Resistance element RE_bComprising a length L_bCross-sectional area A_bAnd resistivity ρ_b. The individual resistance elements can be imagined as, for example, cylindrical, solid and homogeneous wires. As shown in FIG. 6, the resistance element RE_aAnd RE_bAre connected in parallel between the two

bus bars

64 and 66, and a potential E is applied between these two bus bars. In this example, RE_aMay be used to represent the upper wall portion 44a of fining vessel 20, while resistive element RE_bMay be used to represent the lower or second wall portion 44b of fining vessel 20. It is assumed that the two resistance elements are identical, such that L_a＝L_b，A_a＝A_bAnd ρ_a＝ρ_bThe two resistive elements having equal resistance, i.e. resistive element RE_aResistance R of_aEqual to resistive element RE_bResistance R of_b(typically, resistivity ρ is equal to resistance R multiplied by area A divided by length L). Thus, through RE_aCurrent of (I)_aIs equal to pass through RE_bCurrent of (I)_b(other transmission losses are ignored). Resistance element RE_aAnd RE_bTotal current I in_tAre all I_a+I_bOr E/(R)_aR_b/(R_a+R_b)). Substituting the values, assuming E is 10 volts and R is_aAnd R_bEach 5 ohms. Then I_aAnd I_bEach of 2 amperes, total current I_tIs I_a+I_b4 amperes. Assuming that the conversion efficiency is 100%, the total power P consumed as heat is P ═ I_tE. Substituting the above values, P ═ 10 volts × 4 amperes ═ 40 watts.

The previous example assumes a resistive element RE_aAnd a resistance element RE_bThe same is true. Now assume that resistive element RE_aIs reduced so that A is_a＜A_bOther conditions are the same as in the above example. That is, assume that the resistance element RE_aIs in accordance with the previous exampleThe wires in (1) are the same wires, but thinner. This is equivalent to, for example, reducing the thickness of the upper wall portion 44 a. Thus in this example, R_a＞R_b，I_a＜I_b. Using the values of the previous example, assume that resistive element RE_aResistance R of_aNow 6 ohms, resistive element RE_bResistance R of_bNow 5 ohms. I is_aNow 10 volts/6 ohms 1.67 amps, I_b2 amps at 10 volts/5 ohms. I is_{General assembly}The power was reduced to 3.67 amps, with P being 10 volts x 3.67 amps 36.7 watts. In the previous example, RE_aAnd RE_bMay be used to represent the upper portion 44a and lower portion 44b, respectively, of the fining vessel wall. Thus, the power into the glass from the fining vessel may cause the overall glass temperature to drop. However, it is not desirable to cool the glass to a temperature below the initial base case because it is desirable to maintain the same process conditions for melting the glass. Therefore, in order to keep the overall temperature of the molten glass consistent with the temperature in the base case, the power into the molten glass should be kept stable, which can be achieved by, for example, increasing the voltage E applied to the bus bar, in this case about 10.44 volts being used to obtain a power of 40 watts as well. At 10.44 volts, I_aNow about 1.74 amperes, I_bAbout 2.089 amps. Therefore, even for the same power as the basic case, the first resistance element RE_aCurrent I in_aReduced with respect to the base case, second resistive element RE_bCurrent I in_bAnd is increased.

The preceding simple example illustrates that making the thickness of the upper wall portion of fining vessel 20 (i.e., the portion of the fining vessel wall in contact with the gaseous atmosphere above the free surface of the molten glass) thinner relative to the thickness of the lower wall portion (i.e., the portion of the fining vessel wall in contact with the molten glass) reduces the current in the upper wall portion of the fining vessel and thus also reduces the temperature of the upper wall portion. The service life of the fining vessel can be greatly extended even if the temperature is reduced by only a few degrees celsius. Because of the distribution of the increase in current in the lower portion over a much larger cross-sectional area (the lower portion is much larger and much thicker than the upper portion), the increase in current in the lower portion may have only a negligible effect (only a negligible increase in current density).

It should be noted that the above description by means of circuit diagrams is over-simplified, at least for the following reasons: the upper and lower wall portions of the fining vessel are not separate elements but are continuous. The electrical analysis of a real fining vessel is much more complex. However, use is made of

Computer analysis of the computational software has confirmed the results obtained. Therefore, the foregoing description is considered as illustrative of the principles.

In some embodiments, the upper or first wall portion 44a may be made to have a thickness less than the thickness of the lower wall portion by laminating the lower or second wall portion 44b with additional material, such as shown in fig. 7. For example, in the case where the manufacture of the lower wall portion includes rolling a metal sheet into a cylindrical sheet of any thickness, a second metal sheet of any thickness may be rolled into a second cylindrical sheet and joined to the first sheet, for example by welding, to increase the thickness of the first sheet by at least the amount of the thickness of the second sheet. The material of the second layer may be the same or different material as the first layer. Adding one or more layers may increase the overall cost of the fining vessel because it requires the use of additional materials (which in the case of platinum group metals may increase the overall cost significantly). On the other hand, the amount by which the thickness of the upper portion can be reduced is limited by the ability of the fining vessel structure to retain its shape for an extended period of time at temperatures very close to the melting point of the metal, while selectively increasing the thickness of the lower portion is primarily limited by cost. Thus, the initial added cost may be less than the benefit of the long life of the fining vessel.

In another embodiment, as shown in FIG. 8, fining vessel 20 may further comprise a third wall portion 44c located between the first and second wall portions 44a, b. The third wall portion 44c comprises more than t_bThird thickness t_c. Because of the thickness of the third wall part 44cDegree t_cGreater than wall thickness t_aAnd/or t_bCracks that may form in the first wall portion 44a (e.g. as a result of oxidation based thinning) can be prevented by the increased thickness of the wall portion 44c from propagating into the lower or second wall portion 44b of the fining vessel. As shown in fig. 8, the level of molten glass within fining vessel 20 can be controlled such that free surface 50 of molten glass 16 intersects second wall portion 44b, and in some embodiments, can intersect third wall portion 44 c. Methods of controlling the level of molten glass in a glass manufacturing system are known and will not be discussed further herein.

A cross-section of a scrapped fining vessel also shows that oxidative corrosion of the fining vessel tends to begin more often at or near the location where the flange joins the upper or first wall portion 44a, such as within about 16 centimeters (cm) of the intersection of the flange 42 and the upper wall portion 44 a. Thus, in another embodiment as shown in fig. 9, upper wall portion 44a of fining vessel 20 may be locally thickened relative to another portion of upper or first wall portion 44 a.

Fig. 9 illustrates a fining vessel 20 and shows a thickened area of upper wall portion 44a adjacent flange 42. The increased thickness of the upper or first wall portion 44a relative to a short (localized) region of the upper or second wall portion 44b along the longitudinal axis may reduce the current density within that localized portion of the upper wall portion of the fining vessel. This is particularly effective when a local thickening of the upper wall portion 44a is located adjacent the flange 42. Therefore, the upper wall portion 44a between two consecutive flanges 42 may comprise a first length portion 44a₁And a second length portion 44a₂Wherein the second length part 44a₂Is located adjacent and abutting the flange 42, and wherein the second length portion 44a₂Of the upper wall portion t_a2Is greater than the first length portion 44a₁Of the upper wall portion t_a1As shown in the cross-sections of fig. 10 and 11. By continuous flanges is meant that there are no additional flanges between the target flanges. According to the present embodiment, the thickness of the second wall portion 44b may be equal to or greater than the first length portion 44a₁Is thick in the first or upper wall portionDegree (i.e. t)_b≥t_a1). The thickness of the second wall portion 44b may also be equal to or greater than the second length portion 44a₂Of the upper or first wall portion (i.e. t)_b≥t_a2). The following additional simple illustration shown in FIG. 12 may help to understand the effect of thickening at least a portion of the upper portion of the fining vessel.

Reviewing for comparison purposes, FIG. 6 illustrates the first resistive element RE_aAnd a second resistance element RE_bSchematic diagram of the electrical appliance. Resistance element RE_aComprising a length L_aCross-sectional area A_aAnd resistivity ρ_a. Resistance element RE_bComprising a length L_bCross-sectional area A_bAnd resistivity ρ_b. Each of the resistive elements may be, for example, a wire. As shown in FIG. 6, the resistance element RE_aAnd RE_bIn parallel between the two

bus bars

64 and 66. A potential E is applied between the two busbars. Assuming that the two resistive elements are identical, L_a＝L_b，A_a＝A_bAnd ρ_a＝ρ_bThe two resistance elements having equal resistance, i.e. R_a＝R_b(typically, resistivity ρ is equal to resistance R multiplied by area A divided by length L). Also, in this example, RE_aRepresents the upper wall portion 44a of the fining vessel 20, while the resistive element RE_bRepresenting a lower or second wall portion 44b of fining vessel 20. By RE_aCurrent of (I)_aIs equal to pass through RE_bCurrent of (I)_b(other transmission losses are ignored). Total current I_tIs I_a+I_bOr E/(R)_aR_b/(R_a+R_b)). Substituting the values, assuming E is 10 volts and R is_aAnd R_bEach 5 ohms. Then I_aAnd I_bEach of 2 amperes, total current I_tIs I_a+I_b4 amperes. Assuming that the efficiency is 100%, the total power P consumed as heat is P ═ I_tE. Substituting the above values, P ═ 10 volts × 4 amperes ═ 40 watts.

The previous example assumes a resistive element RE_aAnd a resistance element RE_bThe same is true. Now thatReferring to fig. 12, it is assumed that the resistance element RE_aA cross-sectional area of a part of (b) is increased, thereby the resistance element RE_aComprising two sections. That is, assume that the resistance element RE_aIncludes two resistive element sections, a first resistive element section RE_a1And a second resistive element segment RE_a2。RE_a1Comprising a length L_a1Sectional area A_a1Resistivity rho_a1And a resistance R_a1。RE_a2Comprising a length L_a2Sectional area A_a2Resistivity rho_a2And a resistance R_a2. Further assume that the first resistive element segment RE_a1Length L of_a1Is more than the second resistance element section RE_a2Length L of_a2Much longer and second resistive element segment RE_a2Cross-sectional area A of_a2Larger than the first resistive element segment RE_a1Cross-sectional area A of_a1. In other words, it is assumed that the first resistance element RE_aComprising two sections arranged in series at their ends, wherein the second section has a thickness greater than the thickness of the first section, but the length of the first section is much longer than the length of the second section. Assuming the resistivities of the two sections and the second resistive element RE₂So that ρ is equal_a1＝ρ_a2＝ρ_b. Thus, RE can be shown_a1Can control RE_a(as an example of a specific value, consider that for two series-connected resistive elements, one of which has a resistance of 100 ohms and the second of which has a resistance of 5 ohms, the total resistance of the two series-connected resistive elements is 105 ohms, which is not much different from the resistance of the 100 ohm resistive element).

Thus, in this example, the first resistive element RE_aTotal resistance of (2) ═ R_a＝R_a1+R_a2First resistance element RE_aCurrent I in_a＝E/R_a＝E/(R_a1+R_a2)，I_b＝E/R_b. Represents a segment RE_a1And RE_a2Legs of, i.e. resistive elements RE_aCurrent I in_aCan pass through E/R_a1Roughly determined. Current I_bElectricity that would be relevant in figure 6Stream I_bThe same is true. However, the current I of the present embodiment_aWill be in the second resistive element section RE_a2Cross-sectional area A of_a2Upper distribution, cross-sectional area A_a2Larger than the first resistive element segment RE_a1Cross-sectional area A of_a1. Therefore, for the second resistance element section RE_a2Will be less heated than the first resistive element segment RE_a1So that the second resistive element segment RE_a2Will be lower than the first resistive element section RE_a1The temperature of (2). In the case of fining vessel 20, this has the effect of lowering the temperature of the fining vessel at the location of the flange where current enters and/or exits the fining vessel and the current density tends to be greatest.

In another embodiment shown in fig. 13, the upper wall portion 44a of at least a portion of the fining vessel can comprise three length sections: third length portion 44a₃And the first length portion 44a described above₁And a second length portion 44a₂. As previously mentioned, the first length portion 44a₁Comprises a thickness t at a cross section_a1 Second length portion 44a₂Comprises a thickness t at a cross section_a2And t is_a2＞t_a1. Third length portion 44a₃Contains more than t at the cross section_a1And is equal or substantially equal to t_a2Thickness t of_a3. First length portion 44a₁At the second length portion 44a₂And a third length portion 44a₃In the meantime. Second length portion 44a₂Or third length 44a₃One or both of which may be located adjacent to the flange 42.

The cause of hot spots at the upper wall portion 44a of the fining vessel is due to the high current density in the flange at the same planar location as the electrode 49 connecting the flange to the power source. That is, the flange typically includes connection ends or electrodes that extend from the flange and connect to cables or bus bars that supply current to the flange. If the current supplied to the flange is increased to meet the need for a greater degree of heating, such as an accelerated flow of molten glass, the higher current density in the flange and in the fining vessel in the region near the electrodes (where the current is distributed from the electrodes to the flange and fining vessel) may generate a sufficiently high temperature in the flange and/or fining vessel to cause the flange and/or fining vessel to prematurely fail by rapid oxidation of the material comprising the flange and/or fining vessel. This can be better understood with the aid of FIGS. 14 to 16.

FIG. 14 illustrates a side view of a fining vessel including a wall with a thickness that varies circumferentially. Electrode 49 is located on flange 42 closest to the upper or first wall portion 44a of fining vessel wall 44 such that the current (e.g., current density) in the upper portion of the fining vessel wall is greatest in the region of wall 44 in the same plane as electrode 49. That is, the current density at the top of the fining vessel closest to electrode 49 may be greater than the current density that the material of upper fining vessel wall portion 44a can tolerate, possibly resulting in increased heating of the upper portion of the fining vessel in contact with atmosphere 52. This is made clearer by means of fig. 15, which illustrates a cross-section of the fining vessel of fig. 14 at one flange 42. The current that produces the high current density is indicated by arrow 60 and the high current density area is the area marked Za.

To mitigate high current densities in the upper portion of the fining vessel, an electrode 49 may be positioned, as shown in fig. 16, such that the electrode is closest to the lower or second wall portion 44b of the fining vessel, such that a high current density is created in the fining vessel at the location where the fining vessel wall 44 contacts the molten glass, zone Zb. That is, the electrode 49 may be located at the bottom of the flange 42 and extend downward from the bottom of the flange 42. This is particularly advantageous when the thickness of the lower wall portion is greater than the thickness of the upper wall portion.

Examples

FIG. 17 illustrates a graph of temperature along a length of a fining vessel including a substantially uniform cross-sectional wall thickness along the circumferential direction. In addition, as shown in FIG. 18, the fining vessel further comprises a thickening band 75 located between the flanges, the thickening band 75 being adjacent to and abutting the second flange (the rightmost flange in the figures) and extending longitudinally along the fining vessel a distance of about 11 cm. The thickening belt surrounds the clarifying container and has a thickness greater than the wall residue of the clarifying containerThe thickness of the remainder, but the thickness of the thickening belt itself, is substantially uniform. The flanges are located at positions a and B. Curves 70, 72 and 74 represent

The software generated modeling data, circles and triangles represent actual data obtained on the fining vessel by a thermocouple embedded in the refractory insulating material surrounding the fining vessel. The graph shows that the actual data generally mimics the modeled data, helping to demonstrate the feasibility of modeling the temperature along the length of the fining vessel. Curve 70 represents the temperature of the top of the fining vessel as a function of the normalized length, curve 72 represents the temperature along the bottom of the fining vessel as a function of the normalized length, and curve 74 represents the temperature of the fining vessel as a function of the length of one side of the fining vessel along the middle region between the top and bottom of the fining vessel. The data show that the temperature along the top of the fining vessel is about 15-20 degrees celsius higher than the temperature at the sides and bottom of the fining vessel. As previously described, thicker wall sections than one another can reduce the current density at the thicker wall sections, which has been confirmed by simulations that show a sudden drop in temperature just before the flange at B (see fig. 17 from left to right). However, as discussed above, the lack of thickness differences elsewhere along the fining vessel (e.g., thickness variations in the circumferential direction) can result in high temperatures along those portions of the fining vessel. The sudden drop in temperature at the flange, particularly at B, is due to the heat dissipation capability of the flange. That is, each flange functions, at least in part, as a fin capable of dissipating heat both conductively and radiatively. In addition, the flanges are constructed in a configuration to be actively cooled by a cold zone coil located around the perimeter of each flange, through which a cooling fluid flows. FIG. 19 is a graph illustrating Ampere per square millimeter (A/mm) under the conditions of FIG. 17²) Modeled current density in units, where curve 76 represents the current density in the upper wall portion as a function of normalized length, curve 78 represents the current density in the lower wall portion as a function of normalized length, and curve 80 represents the current density as a function of the fining vessel in the middle region between the top and bottom of the fining vesselThe length of the side. (likewise, when viewing FIG. 19 from left to right) the data shows that the current density rises just before the thickened zone, while the current density drops abruptly at the thickened zone.

FIG. 20 illustrates temperature along the length of a fining vessel comprising an upper wall portion and a lower wall portion, wherein the upper wall portion has a smaller cross-sectional wall thickness than the lower wall portion, such as the fining vessel of FIG. 5. The fining vessel of fig. 20 does not contain a thickening belt. The length is shown as a normalized length and the temperature is shown in degrees Celsius (. degree. C.).

Curves

80, 82 and 84 represent the curves by means ofModeling data generated by software. Curve 80 represents the temperature of the top of the fining vessel as a function of the normalized length, curve 82 represents the temperature of the bottom of the fining vessel as a function of the normalized length, and curve 84 represents the temperature of the fining vessel along the sides of the fining vessel as a function of the normalized length of the middle region between the top and bottom of the fining vessel. From the modeling results, as shown in the previous example, the first flange is located at a and the second flange is located at B. The data shows that the temperature along most of the top of the fining vessel is about 5-10 degrees celsius lower than the temperature at the sides and bottom of the fining vessel, except at the flange near position B, which shows an increase in temperature compared to the bottom. This occurs because of the presence of the second flange at B. The increase in temperature may be mitigated by disposing the electrodes to extend downwardly from a flange closest to the bottom of the fining vessel, or by including a thickening band, or at least having an upper portion including a thin first upper portion and a thick second upper portion. Fig. 21 is a graph illustrating modeled current density in amperes per square millimeter for the condition of fig. 20.

Curves

86, 88 and 90 are represented by

Modeling data generated by software. Curve 86 represents the current density at the top of the fining vessel as a function of normalized length, curve 88 represents the current density along the bottom of the fining vessel as a function of normalized length, and curve90 represents the variation of the fining vessel current density along the sides of the fining vessel with the normalized length of the middle region between the top and bottom of the fining vessel.

The graph shows that the current density is generally uniform around the circumference of the fining vessel as a result of the circumferential thickness varying between the two flanges over a medium length of the fining vessel (as indicated by the current densities at the top, bottom, and midpoint), but also shows that the current density rises at the flanges due to the presence of the flanges, as the flanges function to direct all of the current in the fining vessel into or out of the fining vessel.

Thus, these flanges may be considered as nodes that are pooled or distributed. The effect of this increased current density at the flange in the fining vessel, which ultimately results in a temperature increase, can be mitigated by including a thickened band as described above, or more preferably, by including a thick second upper portion, as the modeling results show, including a thickened band around the entire perimeter of the fining vessel does not have a significant effect on the temperature in the lower portion of the fining vessel. Thus, using a thin portion only in the upper portion of the fining vessel represents a cost savings over precious metals relative to increasing the thickness of the fining vessel around the entire circumference.

It should be noted that although the above embodiments are described in the context of a fining vessel, the principles and configurations disclosed herein may be applied to other vessels for delivering molten glass, regardless of the presence or absence of a free surface of molten glass within the vessel. For example, the principles and configurations disclosed herein may be applied, in part or in whole, to connecting

conduits

18, 24, 30, agitation vessel 22, delivery vessel 28, outlet conduit 30 and inlet 32, or any other metal vessel, particularly those that are directly electrically heated.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments without departing from the spirit and scope of the embodiments of the invention. Thus, it is the intention of the inventors to cover modifications and variations of these embodiments, provided they come within the scope of the appended claims and their equivalents.

Claims

1. A molten glass delivery apparatus, comprising:

a container comprising a wall comprising a first wall portion disposed at a top of the container and a second wall portion disposed at a bottom of the container;

a first flange surrounding the vessel and a second flange surrounding the vessel, the second flange being spaced apart from and continuous with the first flange, the first and second flanges being configured to conduct electrical current through the wall between the first and second flanges, the first and second flanges each further comprising an electrode extending therefrom and closest to the first wall portion, the first wall portion comprising a first length portion and a second length portion, the second length portion abutting the second flange;

wherein in a first cross section of the wall containing the first length portion the thickness of the first length portion is less than the thickness of the second wall portion and in a second cross section of the wall containing the second length portion the thickness of the second length portion is greater than the thickness of the first length portion.

2. The molten glass delivery apparatus according to claim 1, wherein a thickness of the second wall portion is greater than a thickness of the second length portion.

3. The molten glass delivery apparatus according to claim 2, wherein the first wall portion further includes a third length portion adjacent the first flange and spaced apart from the second length portion, and wherein in the third cross-section including the third length portion, a thickness of the third length portion is equal to a thickness of the first length portion.

4. The molten glass delivery apparatus according to claim 3, wherein the second wall portion is laminated and comprises a first metal layer and a second metal layer.

5. The molten glass delivery apparatus according to claim 4, wherein the metal of the second metal layer is different from the metal of the first metal layer.

6. The molten glass delivery apparatus according to claim 1, wherein a thickness of the second wall portion is uniform.

7. The molten glass delivery apparatus according to claim 1, wherein the vessel is a fining vessel.

8. The molten glass delivery apparatus according to claim 1, wherein the wall comprises platinum, rhodium, palladium, iridium, ruthenium, osmium, or alloys thereof.

9. The molten glass delivery apparatus according to any one of claims 1-7, wherein the first flange and the second flange comprise a metal of platinum, rhodium, palladium, iridium, ruthenium, osmium, or alloys thereof.