Device for guiding a glass melt

Abstract

The invention relates to a device (20) for guiding a glass melt, comprising a channel (23), wherein the device forms a forehearth section or a portion of a working tank, the glass melt (30) is guided in the channel (23) along a flow direction from an inlet to an outlet, the channel (23) is covered by a superstructure (25), the superstructure extends above the surface of the glass melt and encloses a space above the glass melt along the channel, and a plurality of resistance heating elements (40) are arranged in a row in each of two opposite heating portions of the space above the two outer regions of the glass melt, the outer regions extending in the flow direction. In order to homogenize the temperature distribution and reduce the maintenance complexity, each heating portion is additionally equipped with a plurality of radiating elements (45) which are arranged one behind the other and at a distance to one another along the flow direction and protrude from the respective lateral portion of the superstructure into the space in the transverse direction such that a central space portion between the two opposite heating portions remains free, wherein each radiating element (45) has an elongate boat shape with a depression (47), the depression being surrounded by a lateral wall (46) at a first end lying opposite the respective lateral portion (26) of the superstructure and at at least two sides which enclose the first end, the lateral wall forming an inner upper edge line; each radiating element is situated between an individual resistance heating element or a group of resistance heating elements of the respective row and the surface of the glass melt in such a way that the depression (47) faces the associated resistance heating element(s) (40); and each radiating element (45) at least partly absorbs the thermal energy generated by the associated resistance heating element(s) and emits same onto the underlying glass melt via the radiating element surface facing the glas

Description

[0001] Device for guiding molten glass

[0002] DESCRIPTION

[0003] The invention relates to a device for guiding molten glass, wherein the device has a channel in which molten glass is guided in a flow direction from the direction of a glass melting tank from an inlet to an outlet in the direction of a shaping device, wherein the channel is covered with a superstructure, the superstructure extending above the surface of the molten glass and enclosing a space above the molten glass along the channel. The invention further relates to a system for melting glass with such a device for guiding the molten glass.

[0004] To manufacture products from solidified molten glass, systems are used that first produce the molten glass in a melting tank by melting solids and, if necessary, cullet. The molten glass is then directed into one or more channel- or trough-like structures. Such a trough-like structure carries the molten glass to the shaping unit and is also called a working tank, working tank section, distribution channel, feeder, feeder channel, feeder duct, forehearth, or forehearth section. Depending on the application and type of glass, these trough-like structures have a specific design in sections along the flow of the molten glass, with each section being referred to as a section. There are also trough-like structures in use that have the same design along their entire length and thus comprise only a single section.The sections often exhibit varying depths of molten glass, with the depth frequently decreasing towards the forming device. The device for guiding molten glass discussed below thus corresponds to a section of a trough-like device or describes the structure of the trough-like device along its entire length in the direction of glass flow. The device for guiding molten glass is hereinafter referred to as the pre-hearth section. Such a device explicitly includes a section of a working tank.

[0005] The device for guiding the molten glass (forehearth section) typically has a trough in which the molten glass flows along a defined direction to a shaping unit. The trough is covered by a superstructure that extends above the molten glass. This superstructure can be divided into a roof section and two side sections. Together with the molten glass, the superstructure encloses a space above the molten glass, in which an atmosphere typical for the respective glass melt develops, consisting of various gases and reaction products.

[0006] The pre-hearth section has, among other tasks, the task of conveying the molten glass to the forming unit with the most homogeneous temperature distribution possible. This also ensures a homogeneous viscosity of the glass at the forming unit, which has a positive effect on production output through lower reject rates. The temperature distribution of the molten glass in the pre-hearth section is primarily influenced by two factors. Firstly, the adhesion of the molten glass to the bottom and sides of the trough leads to a reduction in flow velocity in the immediately adjacent areas of the molten glass. This results in a comparatively higher flow velocity for the molten glass located in the central area of ​​the trough, and thus also a greater exchange with the incoming flow of glass, leading to a greater energy input in this area.In the outer areas of the molten glass, the flow velocity is comparatively lower. Secondly, the temperature difference between the molten glass and the surroundings of the respective forehearth section is several hundred degrees. Since the flume is generally made of highly thermally conductive glass contact material (refractory material) and the superstructure is composed of a more thermally insulating material, a large portion of the heat energy from the molten glass flowing through the flume is transferred to the surroundings via the flume. The substructure is also well insulated. Both of the factors described above create a temperature gradient and a gradient in flow velocity from the center of the molten glass flow through the flume towards the areas (edge ​​regions) of the molten glass located near the inner flume wall, which are referred to below as the outer areas.

[0007] An improvement in the homogeneity, particularly the temperature distribution of the molten glass between the center of the flow and the outer areas, is achieved in many known forehearths, for example, by actively cooling the central area of ​​the molten glass flowing in the channel and heating the cooler outer areas. However, forehearths also exist that do not require active cooling in the central area. In such forehearths, only the outer areas are heated.

[0008] In the prior art, such measures include, for example, the lateral installation of numerous mixed-gas burners arranged in a row to heat the outer areas of the glass melt. Optionally, radiative cooling, direct air cooling, or indirect air cooling is also employed in the central superstructure section located above the central area of ​​the glass melt. In radiative cooling, openings are provided in the central superstructure section that are more or less covered by movable stone slabs, thereby generating cooling through radiative losses to the surroundings. In direct air cooling, cooling air is blown into the central space above the central area of ​​the glass melt, allowing the cooling air to reach the glass surface.Indirect air cooling is generated by cooling air flowing into an enclosed cooling air space in the superstructure, thereby creating a temperature sink in the superstructure, which causes radiation losses in the central area of ​​the glass melt.

[0009] As part of the decarbonization of the glass industry, attempts have been made for some time to utilize renewable energies. In this context, concepts have been proposed for heating forehearths with electrical energy. The molten glass can be heated directly using electrodes that extend into the molten glass. The molten glass itself provides resistance, leading to local heating in the area penetrated by the current. This technique is particularly suitable for reducing glass, as the metallic electrodes (e.g., molybdenum electrodes) used in this type of glass have a longer lifespan. This heating method is only conditionally suitable for oxidizing glass, as the molten glass reacts more strongly with the metallic electrode material, causing the reaction products of the electrode material to enter and contaminate the molten glass.Alternatively, oxide / ceramic electrode materials can be used, but these have a short lifespan due to their ceramic structure. Another disadvantage of direct electrical heating is the risk of the electrode material evaporating if the glass level in the forehearth drops significantly, which can occur in various situations, such as a batch plant failure during continuous production. This is a particular concern in a forehearth section located near the molding unit, as the forehearth flume depth often decreases towards the molding unit. Alternatively, the molten glass can be heated indirectly by using resistance heating elements positioned in the space between the surface of the molten glass and the superstructure, or in one or more spaces in or on the flume or superstructure. This was described, for example, in document DE 3528332 A1.In this case, the heat is transferred from the resistance heating element by radiation and / or by conduction through the air and / or through the material of the superstructure or the trough.

[0010] Resistance heating elements located in the space above the surface of the molten glass are subject to material degradation due to reactions with surrounding gases during continuous use in the forehearth atmosphere. This can cause individual grains or flakes to enter the molten glass, rendering it unusable for further processing in the molding equipment or creating defects in the products manufactured from the molten glass. To prevent such contamination, it has been proposed (see US 2016 / 0122222A1) to position the indirectly acting resistance heating elements above a step in the wall of the flume or a side section of the superstructure, thus preventing grains and flakes from directly entering the molten glass. However, this leads to an undesirable widening of the forehearth and consequently to reduced efficiency.In this variant, it is generally not possible to arrange two or more than two resistance heating elements side by side in a transverse direction that runs perpendicular or at a predetermined angle to the flow direction of the molten glass, so that a further resistance heating element would not be available for pre-tempering or emergency phase heating.

[0011] Therefore, in some applications of indirect electrical heating, shields were used that extended over the entire length and / or width of the respective forehearth section (see documents US 2016 / 0122222A1 and DE 10 2004 006 619 A1) and were positioned below the resistance heating elements. However, these shields have the disadvantage of reacting sluggishly to changes in heating parameters, thus undesirably increasing the system's response time to such changes. Furthermore, in the variant where the shields extend over the entire width of the forehearth, achieving the desired differential heating in the outer areas and the central section of the chamber—intended to reduce the temperature gradient in the glass melt—is difficult and requires significant energy expenditure, as the shield tends towards temperature equalization according to the second law of thermodynamics.Another disadvantage of such shields is that their size, bulk, and the deep integration into the superstructure required for their construction make them difficult to replace or repair. Furthermore, temperature differences between the exterior and interior of a shield spanning the entire width of the forehearth place considerable mechanical stress on it.

[0012] The object of the present invention is therefore to provide a device for guiding a glass melt (forehearth section) which, when electrically heated, ensures good homogenization of the temperature distribution across the glass melt. Furthermore, the overall maintenance effort for heating the forehearth should be reduced. The same object applies to the system for melting and transporting glass.

[0013] The above problem is solved by the device for guiding a glass melt (forehearth section) with the features of claim 1 and a system for melting glass with the features of claim 15. In particular, the above problem is solved by a device for guiding a glass melt (forehearth section) with

[0014] a channel in which the molten glass is guided along a flow direction from an inlet, which receives molten glass, for example, from the direction of a glass melting tank, to an outlet, e.g., in the direction of the inlet of a forming device,

[0015] wherein the channel is covered with a superstructure, the superstructure extending above the surface of the molten glass and enclosing a space above the molten glass along the channel,

[0016] wherein in two opposing heating sections of the space above the molten glass, which are located above the two outer areas of the molten glass extending in the direction of flow, a plurality of resistance heating elements are arranged in a row, wherein the resistance heating elements project into the space, i.e., into the respective heating section, and each introduces thermal energy into the device for heating the molten glass by means of a resistance section, wherein the resistance heating elements of a row are arranged individually or in groups of at least two resistance heating elements one behind the other along the direction of flow, wherein the at least two resistance heating elements of a group lie next to each other in a transverse direction from the respective side section of the superstructure towards the center of the space, perpendicular or oblique to the direction of flow,

[0017] wherein in each heating section a plurality of radiant elements are additionally provided, which are arranged one behind the other and spaced apart from each other along the direction of flow, project from the respective side section of the superstructure in the transverse direction and extend into the space in such a way that a central space section between the two opposing heating sections remains free, wherein each radiant element has an elongated boat shape with a depression, wherein the depression is surrounded at a first end opposite the respective side section of the superstructure and on at least two sides enclosing the first end by a side wall which forms an inner upper edge line,

[0018] wherein each radiant body is arranged between a single resistance heating element or a group of resistance heating elements of the respective series and the surface of the glass melt such that the recess faces the associated resistance heating element(s), that an area is enclosed by the inner upper edge line of the side wall of the respective radiant body when projected onto the plane of the surface of the glass melt, and that within this area there is a projection of the respective resistance section(s) of the associated resistance heating element(s) into the same plane,

[0019] Each radiant element absorbs at least some of the thermal energy generated by the associated resistance heating element(s) and transfers it to the underlying molten glass via its surface facing the molten glass. The above device for guiding molten glass (pre-hearth section) guides the molten glass in the direction of flow from an inlet to an outlet of the device. At the inlet of the device, the molten glass has a specific inlet temperature. The molten glass can enter the pre-hearth section from a glass melting tank, for example, and a further pre-hearth section may be arranged between the glass melting tank and the pre-hearth section. Before entering the respective pre-hearth, the molten glass may have been guided from a glass melting tank, for example, through a passage with a riser.At the outlet of the device, the molten glass should have a predetermined exit temperature, which is generally lower than the inlet temperature. The outlet guides the molten glass towards a forming unit. However, it is also conceivable that the temperature at the inlet and outlet should be approximately the same, or higher at the outlet than at the inlet. At the outlet of the pre-hearth section, the molten glass can enter a forming unit or another pre-hearth section. Immediately upstream of the forming unit, for example, an equalizing zone or an intermediate area, in which the molten glass is heated exclusively, and a spout may be arranged. In the following, the term "device for guiding a molten glass" explicitly includes not only a pre-hearth section but also a section / part of the work tank, even though, for the sake of simplicity, these will be uniformly referred to as the "pre-hearth section" in the following text.

[0020] According to the invention, the pre-hearth section has a channel in which molten glass is guided substantially along the flow direction from the inlet (e.g., outlet of a glass melting tank, an upstream pre-hearth section, or a working tank section) to an outlet (e.g., inlet of a forming device or inlet of another pre-hearth section). The U-shaped channel consists of a refractory glass contact material, for example, at least one material from the group containing AZS (aluminate, zirconate, silicate, including aluminum, zirconium, and silicon oxides) and high-alumina material such as corundum or mullite (each melt-cast or pressed), and, with its channel shape extending in the flow direction of the molten glass, receives the entire flow of molten glass. The surface of the molten glass is always below the top edge of the channel. The cross-section of the channel is, for example, U- or W-shaped.The flume is covered by a superstructure that extends above the surface of the molten glass and encloses a space above the glass along the flume. The superstructure is the same length as the flume in the direction of flow and consists of straight or curved plates or vaults made of refractory material, or of a brick-and-mortar structure, also made of refractory material. The superstructure material can be, for example, a dimensionally stable and temperature-resistant material such as Silimanti, Mullit, Zirconmullite, or silica, which is insulated in the next layer. Due to its covering function, the superstructure minimizes gas and heat losses and separates the gases escaping from the molten glass from the environment or allows their controlled release. The superstructure comprises two side sections and a central section located between them.The side sections laterally separate the space above the molten glass, and the central section defines the upper boundary of this space. Therefore, the central section is also referred to as the roof section. The space between the surface of the molten glass and the superstructure contains the gases in an atmosphere typical for the respective glass melt. Furthermore, as described in more detail below, the space between the superstructure and the surface of the molten glass allows for the reduction of the temperature and flow velocity differences in the molten glass explained above, thereby homogenizing it and reducing the reject rate. The space between the superstructure and the surface of the molten glass is also referred to as the heated space.

[0021] The pre-hearth section according to the invention has a total of three sections in the space above the molten glass, each extending along the surface of the molten glass or along the superstructure in the direction of flow and arranged side by side. The space above the molten glass is divided into two opposing heating sections and an intermediate central section. The heating sections are located above the two outer areas (edge ​​regions) of the molten glass that extend in the direction of flow. As described in more detail below, thermal energy is introduced into the outer areas of the molten glass by means of the two heating sections to increase its temperature. In contrast, no substantial thermal energy is introduced into the central section; instead, the molten glass is cooled in its central region.

[0022] In the two heating compartments of the chamber, near the side sections of the superstructure, a multitude of resistance heating elements are arranged in a row. These elements project into the chamber and each introduces heat energy into the apparatus to heat the molten glass via a resistance section. The resistance section is the part of the heating element that generates the heat energy (e.g., through a reduced cross-section or a material with a higher electrical resistance compared to the other sections). The resistance heating elements can project downwards (vertically) from the central section (roof section) of the superstructure or laterally (horizontally) from a side section of the superstructure.The resistance heating elements are, for example, heating elements based on MoSi₂ or SiC, or they can have at least one metallic heating coil (heating wire) made of a metal alloy, for example, a metal alloy of the FeCrAl or NiCr group, or the like. Such a heating coil can also be embedded in a refractory material. In each heating section, the resistance heating elements can be arranged in a series of individual, flow-directed resistance heating elements. Alternatively, groups of at least two resistance heating elements can be arranged flow-directed.In this configuration, at least two resistance heating elements of a group are arranged side by side in a transverse direction, with the transverse direction running from the respective side section of the superstructure towards the center of the space, either perpendicular or oblique to the flow direction. In the case of an oblique direction, the angle to the flow direction is, for example, greater than 70°. The at least two adjacent resistance heating elements can be arranged in various ways; for example, they can be oriented in the same or different directions relative to the flow direction. If oriented in the same direction, the resistance heating elements, each of which has two electrical connections and runs between these connections in a loop, U, pin, or helix shape, can be arranged parallel to each other in the transverse direction, parallel to each other in the flow direction, or aligned along a line running in the transverse direction.

[0023] The resistance heating elements can have a U-shape, a helical shape, or a pin shape, optionally embedded in a refractory material, and project from the roof section or the side section of the superstructure in the direction of the radiant body described in more detail below, and optionally be partially recessed in the radiant body's recess. The individual resistance heating elements can extend along the transverse direction or along the flow direction. In a group, the resistance heating elements can be arranged, for example, parallel to one another or aligned along a line, for example, in the transverse direction. However, they can also be oriented in different directions. According to the invention, the resistance heating element(s) should be enclosed by the inner boundary line of the radiant body when viewed in each case as projected onto the plane of the surface of the molten glass.The resistance heating elements can be arranged separately in each of the two rows running through the heating sections. Alternatively, a resistance heating element can overlap the two opposing heating sections by extending transversely across the entire width of the fore-hearth section. However, such a resistance heating element has at least one separate resistance section in each of the two heating sections of the room.

[0024] The distance between adjacent radiant bodies in the same heating section in the direction of flow (relative to their center line running along the transverse direction) is, for example, at least 80 mm, e.g. from 80 mm to 500 mm, for example from 100 mm to 400 mm.

[0025] The pre-hearth section according to the invention also has a plurality of radiant elements in each heating section, which are arranged one behind the other and spaced apart from each other along the flow direction. Each radiant element projects transversely from the respective side section of the superstructure and extends into the space in such a way that a central space section between the two opposing heating sections remains free. The radiant elements therefore represent individual elements spaced apart from each other in the flow direction, with each radiant element projecting into the space from the side section of the superstructure, but only to the extent that a central space section above a central area of ​​the molten glass remains free. Furthermore, the radiant elements have a special shape that enables their mode of operation according to the invention, which is described in detail below. Each radiant element is a passive body that does not, i.e.,Unlike the numerous resistance heating elements, this unit is connected to a power supply. Each radiant body has an elongated, boat-shaped form with a longitudinally elongated depression that has a predetermined length in the transverse direction and a predetermined width in the direction of flow. The depression is open at the top, towards the resistance heating element(s), and closed at the bottom, towards the surface of the molten glass. The depression is enclosed by a side wall at a first end opposite the respective side section of the superstructure (in the longitudinal direction of the elongated radiant body) and on at least two longitudinal sides of the depression that enclose the first end. The first end of the depression is therefore located at the end of the radiant body that is furthest from the side section of the superstructure.The side wall of the jet body forms the boundary of the recess on at least three sides. The longitudinal sides of the recess run parallel to the transverse direction, and the first end of the recess runs essentially in the direction of flow. The side wall extends continuously around the recess and transitions from the bottom of the recess in an angular or rounded shape. The side wall can also close off the second end of the recess, which is opposite the first end and adjacent to the respective side section of the superstructure from which the jet body projects. Furthermore, the side wall forms an inner upper edge line, which is the uppermost and innermost line of the side wall at the transition between the inside of the jet body and the upper end face.This inner upper boundary line thus defines the inner and upper side wall of the radiating body and is used to describe the position of the individual resistive element or group of resistive elements relative to the radiating body. The underside of the radiating body's base can, for example, run parallel to the surface of the molten glass, i.e., horizontally, or at an angle to this surface, such that the base is higher (i.e., farther from the surface of the molten glass) at the first end of the depression than at the second end of the depression.

[0026] According to the invention, each radiant element is arranged between a single resistance heating element or a group of resistance heating elements of the respective series and the surface of the molten glass such that the recess faces the associated resistance heating element(s). Thus, if the series of resistance heating elements consists of individual resistance heating elements arranged one behind the other, each such individual resistance heating element is assigned to a radiant element, and a radiant element is provided below each individual resistance heating element. Similarly, if the series of resistance heating elements consists of groups of several resistance heating elements arranged one behind the other, for example, two or three resistance heating elements, each group is assigned such a radiant element, and a radiant element is provided below each group of resistance heating elements.The individual or grouped resistance heating elements of the respective heating sections are not only arranged above the radiant bodies, but also positioned in a specific way. When a projection of the inner upper edge line of the side wall of the respective radiant body onto the plane of the surface of the molten glass is considered, this edge line encloses an area in the projection. Furthermore, if the projection of the respective resistance section(s) of the resistance heating element(s) belonging to the radiant body is also considered onto the same plane, these resistance section(s) lie within the area enclosed by the edge line in the projection. This describes how, viewed in a direction perpendicular to the surface of the molten glass, the resistance section(s) of the radiant body belonging to it (i.e.,The resistance heating element(s) located above the radiant body are situated within an area enclosed by the side wall. The resistance section(s) are thus located above the recess of the respective radiant body. A further characteristic of each radiant body is that it absorbs at least some of the heat energy generated by the associated resistance heating element(s) (i.e., located above the radiant body) from the surrounding atmosphere and transfers it to the molten glass below via its surface facing the molten glass. In many cases, the majority of the heat energy generated by the resistance heating element(s) is absorbed by the associated radiant body. The surface of the radiant body facing the molten glass is specifically composed of the outer surface of the side wall and the underside of the recess's base.

[0027] The beam body is made, for example, of a ceramic material from the group comprising borosilicates, silicon carbides, aluminum nitrides, and aluminum oxides, and can be manufactured by melt casting, ceramic pressing, and / or slip casting. In one embodiment, the beam body can incorporate a reinforcing material, such as glass fibers or metal pins.

[0028] The special mode of operation and the advantages of the pre-hearth section according to the invention result from the special shape of the radiant elements and from the arrangement of the radiant elements in relation to the resistance heating elements, which will be explained below. All properties of the pre-hearth section discussed below are equally important in this context.

[0029] The boat-shaped design of the jet bodies allows for the reliable collection of decomposition products that can form on the resistance heating elements during operation of the forehearth section due to degradation. Thanks to the side walls, even larger falling decomposition products do not enter the glass melt below. Contamination of the glass melt by these decomposition products is therefore effectively prevented.

[0030] The boat-shaped element also possesses very good mechanical high-temperature dimensional stability due to stabilization by the side wall, so that the jet body does not sag downwards towards the molten glass during operation of the forehearth section at the typically used high temperatures, or only very slightly. Such a change in shape is—if it occurs at all—significantly less than with conventional, plate-shaped shielding elements discussed above. In an embodiment that exhibits particularly good mechanical stability, the height of the side wall (dimension in a direction perpendicular to the surface of the molten glass) is equal to or greater than the width of the jet body (dimension in the direction of flow).

[0031] The arrangement of the radiant elements in the two heating sections of the chamber, as described above, leaving a central section unheated, allows for effective cooling of the molten glass in its central area, thereby promoting homogenization. This cooling can be achieved in various ways, such as direct or indirect air cooling or radiant cooling, depending on the specific embodiment. Furthermore, the boat-shaped design reduces heat radiation into the central section compared to using resistance heating elements without radiant elements, thus resulting in less heat input into the central area of ​​the molten glass.This is achieved in particular by the side wall section of the radiant body provided at the first end of the recess, which prevents direct heat radiation from the respective resistance heating element into the central chamber. Furthermore, especially under production conditions where the throughput of molten glass is significantly lower than the throughput for which the forehearth section was designed, the radiant body results in a significant homogenization of the heat radiation in the outer areas of the molten glass, thus preventing local overheating and bubble formation.

[0032] As described above, in the heating sections, at least some of the heat energy generated by the resistance heating elements is transferred to the radiant body, which then radiates this heat energy towards the molten glass. The shape of the radiant body causes a large proportion of this radiation to be directed downwards. This radiation pattern differs from that of the resistance heating element itself, which radiates in all directions. The radiation behavior of the radiant body is determined by the distance between the resistance section(s) of the associated resistance heating element(s) and the radiant body, the height of the side wall, and the size of the radiant body (including side wall thickness). The forehearth section can be optimally adapted to the specific application (the type of glass, the operating temperature range, and the expected temperature variation) by appropriately varying these parameters.

[0033] For example, a side wall with a low height and large spacing between adjacent heating elements in a row causes the respective resistance heating element(s) to heat partly indirectly via the heating element and partly directly to the molten glass. This is advantageous in operation for small, confined forehearths or working tanks.

[0034] In another example, when using radiant elements that completely enclose or surround the resistance sections of the associated resistance heating element(s) within the respective recess, a direct interaction between the resistance section(s) and the inner wall is created, thus achieving a uniform load distribution across these resistance sections. If necessary, the influence of the gas atmosphere in the heated space of the forehearth section on the resistance section material can be reduced. Both effects lead to an extension of the service life of the resistance heating elements.

[0035] From the above explanations, it is clear that the pre-hearth section, with its heating elements of the shape described above and in the arrangement discussed above, can achieve improved homogenization of the temperature distribution in the molten glass by means of electrical heating, without the risk of contamination of the molten glass. The service life of the resistance heating elements can also be extended. This results in overall more cost-effective operation.

[0036] Further advantages result from subsequent developments of the invention.

[0037] In one embodiment, a lower end section of the resistance section of the associated single resistance heating element or of the at least two resistance heating elements of the associated group projects into the recess of the respective radiant body. In this embodiment, the radiant body encloses the resistance section of the resistance heating element(s) and effectively absorbs the heat energy generated by the resistance section in order to then transfer it towards the molten glass. For example, the resistance section projects at least 10 mm into the recess of the radiant body. In another embodiment, the entire resistance section is enclosed by the radiant body, i.e., the resistance section projects into the recess of the radiant body with at least its entire length (dimension in a direction perpendicular to the molten glass).In the latter case, as described above, the service life of the resistance heating element(s) is increased. In one embodiment, the lower end of the associated individual resistance heating element, or the lower end of each of the at least two resistance heating elements in the associated group, is located a maximum of 200 mm away from the upper edge of the respective radiant body. The lower end of the resistance heating element(s) may, for example, be located 10 mm to 200 mm away from the upper edge of the respective radiant body. This results in partially direct and partially indirect heating of the outer areas of the molten glass by the resistance heating element(s). This has the advantage that the resistance heating element can be replaced without having to modify the radiant body.

[0038] In one embodiment, the resistance section of the associated single resistance heating element or the at least two resistance heating elements of the associated group are at a substantially equal distance from the inner surfaces of the side wall of the radiant body in the area of ​​the recess. Since heat is also transferred from the (hot) side wall of the radiant body towards the resistance heating element(s), a uniform distance between the side wall and the resistance section(s) also has a positive effect on the service life. Conversely, an uneven load would lead to increased wear of the resistance section(s).

[0039] In one embodiment, the multitude of jet elements are designed to be interchangeable. For this purpose, corresponding openings are provided in the respective side section of the superstructure. The jet element can be inserted and removed from the outside of the fore-hearth section into the heated space of the fore-hearth section, and thus replaced, along these openings. The opening is only slightly larger than the jet element itself, allowing it to be moved precisely through the opening into the superstructure. The jet element is secured, for example, by a wedge-shaped superstructure block, such as one on its underside. The superstructure block is then inserted into an opening above, below, or to the side of the jet element, until the jet element is wedged and thus secured within the opening.Other methods for installing new baffles in the side section of the superstructure are also conceivable. The baffle can then be replaced very quickly and easily when it needs to be replaced (e.g., due to excessive filling of the recess with degradation-related grains or flakes, or due to degradation-related damage to the baffle itself). This is done, for example, by pulling out the superstructure block that is jamming the baffle element and moving the baffle out of the opening. A new baffle is then installed in the same way, which can be done while the forehearth section is in operation. Replacing the baffle is also very easy because it is a more manageable object than, for example, a shield extending along the entire length of the forehearth.In one embodiment, the total length of the radiant element in the transverse direction is at least 100 mm. For example, the radiant element has a total length of 100 mm to 800 mm, e.g., from 100 mm to 700 mm, or e.g., from 100 mm to 500 mm. The length depends, for example, on the dimensions of the respective pre-heating section and is dimensioned such that, with two radiant elements positioned opposite each other in opposing heating sections of the heated room, a central section of the room remains unobstructed. The width of this central section in the transverse direction can, for example, be at least 50 mm. For example, the central section has a width of 100 mm to 5000 mm.

[0040] In one embodiment, the aerator can be arranged in the forehearth section such that it is attached above a step in the respective side section of the superstructure, with the aerator projecting partially into the heated space. This means that the aerator projects with a first section away from the step and into the heated space, and with a second section, viewed in a direction perpendicular to the surface of the molten glass, overlaps the side section (step) of the superstructure. Therefore, in this embodiment, the aerator projects into the step of the side section of the superstructure with a portion of its total length, for example, at least 1 / 4 of its total length.From the respective side section of the superstructure (including any step), the respective radiant element projects into the heated space for a length (in the transverse direction) of at least 25 mm, for example, a length of at least 50 mm. For example, the first section of the radiant element projecting freely into the heated space from the side section of the superstructure has a length (in the transverse direction) of 25 mm to 500 mm, for example, from 50 mm to 250 mm. Similarly, the recess projects into the heated space with a first section, for example, with a length of at least 20 mm, for example, with a length of at least 45 mm. For example, the section of the recess projecting into the heated space has a length of 20 mm to 495 mm, e.g., from 45 mm to 245 mm.In this embodiment, with an associated group of two resistance heating elements, the second resistance heating element can be arranged above the stage in the second section of the radiant body, and the first heating element in the first section of the radiant body, which projects into the heated space. The second heating element is typically used for pre-tempering or emergency phase heating, while the first heating element is used to heat the outer areas of the molten glass during the regular operation of the forehearth section.

[0041] In one embodiment, the width of the jet body in the flow direction is at least 50 mm. For example, the jet body has a width of 50 mm to 300 mm, e.g., from 50 mm to 250 mm. The width also depends on the arrangement of the resistance heating elements in relation to the jet body, the flow direction, and their width, which is explained in more detail below.

[0042] In one embodiment, the width of the jet body's recess in the flow direction is at least 20 mm and / or the length of the jet body's recess in the transverse direction is at least 60 mm. For example, the jet body's recess has a width (in the flow direction) of 40 mm to 290 mm, e.g., from 55 mm to 240 mm. Similarly, the jet body's recess has a length (in the transverse direction) of 90 mm to 990 mm, e.g., from 90 mm to 690 mm, e.g., from 90 mm to 490 mm. In each case, the width of the recess is greater than the total width of the associated resistance element(s) in the flow direction. Similarly, the length of the recess is greater than the total length of the associated resistance element(s) in the transverse direction.This ensures that a projection of the respective resistance section(s) of the associated resistance heating element(s) into the plane of the surface of the glass melt is located within the area that is surrounded by the edge line when the inner upper boundary line of the side wall is projected into the same plane.

[0043] In one embodiment, the height of the side wall of the radiant body is at least 30 mm. The side wall of the radiant body has a height of, for example, 30 mm to 500 mm, or 50 mm to 300 mm. The height of the side wall is measured between the underside of the base and the top edge of the side wall. In another embodiment, the wall thickness of the side wall of the radiant body is at least 3 mm. The side wall of the radiant body has a wall thickness of, for example, 4 mm to 50 mm, or 5 mm to 30 mm. Such a side wall provides the radiant body with good mechanical stability and good high-temperature form stability at the temperatures prevailing in the heated room, which range from 1000 °C to 1550 °C. The base of the radiant body can have a wall thickness that is approximately equal to the wall thickness of the side wall of the radiant body.Furthermore, the beam body can also have a section of side wall at its second end, facing the superstructure, which closes off the recess in this direction. The wall thickness of this side wall section is, for example, the same as the wall thickness in the other sections of the side wall described above, but it can also be made greater (up to twice as large) to ensure good stability in the attachment of the beam body to the side section of the superstructure.

[0044] In one embodiment, the wall thickness of the side wall of the jet body is greater at the top than at the bottom; that is, the side wall of the jet body tapers from the upper end facing the superstructure (i.e., from the end forming the upper edge line) towards the bottom of the jet body. This can increase the radiation emitted by the jet body towards the molten glass. Alternatively, the tapering of the side wall can occur from the bottom of the jet body towards the superstructure, with both variants preferably only affecting the section of the jet body that projects transversely from the side section of the superstructure and into the space above the molten glass.Alternatively or additionally, the tapering of the side wall of the radiant body can be such that the side wall of the section of the radiant body projecting into the space above the molten glass is thinner (i.e., has a smaller wall thickness) at its first, front end facing the central section of the space than at the end of the projecting section of the radiant body that is closest to the side wall of the superstructure. Due to the respective reduction in the wall thickness of the side wall, the width of the radiant body (see, for example, width B in Fig. 4) can decrease in the respective direction of the tapering, or the width of the recess (see, for example, width BV of the recess in Fig. 4) can increase.By tapering the wall thickness of the jet body's side wall towards the central section and thereby reducing the material at the jet body's front end, the mechanical stability of the entire jet body can be improved, as the leverage effect of the material at the front end is reduced. This tapering is also implemented in the side wall section extending essentially parallel to the flow direction, i.e., the side wall section located at the first end of the jet body's recess. The first end of the recess is the end of the recess opposite the respective side section of the superstructure. Depending on the initial wall thickness of the jet body, the tapering of the wall (i.e., the reduction in wall thickness relative to the original wall thickness) can range from fractions of a millimeter to a few millimeters.

[0045] In one embodiment, the height of the side wall of the radiant body and the arrangement of the radiant body are designed such that the resistance section of the associated individual resistance heating element, or the respective resistance sections of the at least two resistance heating elements of the associated group, are enclosed along their entire height by the side wall of the radiant body. Here, the resistance heating element projects, for example, downwards from the central section (roof section) of the superstructure into the recess of the radiant body. For example, the resistance section of a U-shaped MoSi2 resistance heating element (extending in a direction perpendicular to the surface of the molten glass) has a length of 50 mm to 400 mm, e.g., a length of 100 mm to 300 mm.The height of the side wall of the radiant body must be greater than the length of the resistance section by the wall thickness of the base of the radiant body and the distance of the resistance heating element from the base of the radiant body, so that the resistance section is completely enclosed in the recess of the radiant body. As described above, such a design of the radiant body and the positions of the resistance heating element and radiant body can increase the service life of the resistance heating element. In one embodiment, additional heat energy is introduced into the two opposing heating sections of the room by means of a plurality of burners that combust combustible gas and are arranged in the respective side section of the superstructure. For example, pre-hearth burner banks (i.e.,Mixed-gas burners (gas-air, gas-oxygen, natural gas, biogas, hydrogen, and other combustible gases; the burner is also referred to as a single-tube burner) are used in a known manner. This allows for hybrid heating of the opposing heating sections of the room, with heating via the burners being more flexibly controllable than indirect heating via radiant panels. For example, one or at least two burners are provided between two adjacent radiant panels in a heating section, supplying fossil fuel, biogas, (e.g., regeneratively produced) hydrogen, or another combustible gas, for example, in the form of a mixed gas, to the room to be heated from the side section of the superstructure and combusting it to generate heat.

[0046] In one embodiment, the central section of the chamber is cooled by indirect air cooling. This indirect air cooling is achieved, for example, by blowing cooling air into a sealed cooling air chamber located above the chamber of the device, which is enclosed by the superstructure and the surface of the molten glass. The cooled cooling air chamber cools the insulating material of the superstructure and thus acts as a temperature sink, generating radiation losses in the central area of ​​the molten glass. Such indirect air cooling is used, for example, in a first section of the forehearth section, which has a length in the direction of flow that corresponds to two-thirds of the total length of the forehearth section in the direction of flow. In a subsequent section of the forehearth section, extending towards the forming unit, additional radiation cooling can be achieved using a movable plate.

[0047] Alternatively, the pre-cooker section can be operated without additional cooling or with direct air cooling of the central room section.

[0048] In one embodiment, the radiator has a nose-shaped projection (nose, nose-shaped extension) at its end furthest from the side section of the superstructure. This projection extends into a corresponding recess in the roof section of the superstructure, with the recess supporting the radiator when installed. In many cases, the roof section of the superstructure has a downward-projecting bulge extending towards the molten glass, running along the flow direction and separating the two heating sections of the chamber from the central chamber section. In this embodiment, a nose-shaped projection of the radiator can extend into a recess in the roof section, particularly into a recess in a bulge projecting from the roof section, and be supported there by the superstructure, especially by the bulge. The recess can be a through-hole (i.e., an opening).The nose-shaped projection extends from the first end of the beam towards the central section of the room. This type of support provides better anchoring of the beam within the space. The nose-shaped projection can, for example, have a transverse length of 50 mm to 150 mm.

[0049] In one embodiment, the nose-shaped projection has a beveled underside (wedge-shaped underside), which facilitates the insertion of the nose-shaped projection into the recess of the roof section and prevents damage to the edge sections of the recess of the roof section during insertion.

[0050] The above task is further solved by a system for melting and transporting glass with a glass melting tank and optionally a working tank arranged downstream in the global flow direction of the glass, wherein the raw materials for glass production and optionally the glass cullet are completely melted in the glass melting tank and optionally in the working tank, wherein the molten glass, after exiting the glass melting tank, enters one or more of the above-described device(s) for guiding a molten glass (preheating section(s)), wherein each device for guiding a molten glass directs it to another device for guiding a molten glass or to a shaping device.

[0051] The above system possesses the advantages and embodiments described above in connection with the device for guiding the molten glass, with regard to the forehearth section. Reference is therefore made to the above explanations.

[0052] Further embodiments of the present invention are explained in detail below with reference to the figures. These figures schematically show...

[0053] Fig. 1 shows a first embodiment of a system according to the invention in a horizontal cross-section,

[0054] Fig. 2 shows a first embodiment of a forehearth section of the system according to Fig. 1 in a perspective view from the front,

[0055] Fig. 3 shows a second embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0056] Fig. 4 shows a section of the fore-hearth section according to Fig. 3 in a horizontal cross-section, Fig. 5 shows a vertical cross-section of a radiant body with resistance heating element of the fore-hearth section according to Fig. 3,

[0057] Fig. 6 shows a front view of the radiator according to Fig. 5,

[0058] Fig. 7 shows the installation of a jet body of the fore-hearth section according to Fig. 3 in a vertical cross-section in the transverse direction of the fore-hearth section, wherein the jet body is shown closed on one side,

[0059] Fig. 8 shows a third embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0060] Fig. 9 shows a vertical cross-section of a radiant body with associated resistance heating element of the pre-hearth section according to Fig. 8,

[0061] Fig. 10 shows a front view of the radiator according to Fig. 9,

[0062] Fig. 11 shows a fourth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0063] Fig. 12 shows a vertical cross-section of a radiant body with associated resistance heating element of the pre-hearth section according to Fig. 11,

[0064] Fig. 13 shows the installation of a jet body of the forehearth section according to Fig. 11 in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0065] Fig. 14 shows a vertical cross-section of a section of a fifth embodiment of a forehearth section in the direction of flow with two jet bodies and associated resistance heating elements,

[0066] Fig. 15 shows a sixth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0067] Fig. 16 shows a vertical cross-section of a radiant body with associated resistance heating element of the pre-hearth section according to Fig. 15,

[0068] Fig. 17 shows a section of the forehearth section according to Fig. 15 in a horizontal cross-section, Fig. 18 shows a seventh embodiment of a forehearth section in a vertical cross-section, wherein the radiator body is shown closed on one side,

[0069] Fig. 19 shows a section of a forehearth section according to Fig. 18 in a horizontal cross-section,

[0070] Fig. 20 shows an eighth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0071] Fig. 21 shows a ninth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0072] Fig. 22 shows a tenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0073] Fig. 23 shows an eleventh embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0074] Fig. 24 shows a twelfth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0075] Fig. 25 shows a thirteenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0076] Fig. 26 shows a section of the forehearth section according to Fig. 25 in a horizontal cross-section,

[0077] Fig. 27 shows a fourteenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0078] Fig. 28 shows a section of the forehearth section according to Fig. 27 in a horizontal cross-section,

[0079] Fig. 29 shows a section of a fifteenth embodiment of a forehearth section in a horizontal cross-section,

[0080] Fig. 30 shows a sixteenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side; Fig. 31 shows a seventeenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side.

[0081] Fig. 32 shows an eighteenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0082] Fig. 33 shows a nineteenth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0083] Fig. 34 shows a twentieth embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0084] Fig. 35 shows a twenty-first embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0085] Fig. 36 shows a twenty-second embodiment of a forehearth section in a vertical cross-section in the transverse direction, wherein the jet body is shown closed on one side,

[0086] Fig. 37 shows a vertical cross-section of a section of a twenty-third embodiment of a forehearth section in the direction of flow,

[0087] Fig. 38 shows a section of the forehearth section according to Fig. 37 in a horizontal cross-section and

[0088] Fig. 39 shows a section of a twenty-fourth embodiment of a forehearth section in a horizontal cross-section.

[0089] Fig. 1 shows a system according to the invention with a glass melting furnace in the form of a U-shaped flame furnace 1 with a regenerator 2, wherein the raw materials and cullet are fed to the glass melting furnace by means of a feeding device 3. The molten glass is produced in the U-shaped flame furnace 1, which then passes through the opening and riser 5 into the working furnace 7. The molten glass is directed laterally from the working furnace into two L-shaped pre-hearths 9 and centrally into two linear pre-hearths 10. From the respective pre-hearth 9, the molten glass passes into shaping devices 13.

[0090] For example, in the U-shaped flame tank 1, soda-lime silicate glass (bottle glass) is produced. This glass leaves the U-shaped flame tank 1 at a temperature of approximately 1330 °C and passes through the flue and riser 5 into the working tank 7, at whose outlets the molten glass has a temperature of 1270 °C. At this temperature, the molten glass enters the forehearths 9, 10, where it is slowly cooled to a temperature of 1200 °C. The aim is for this temperature to be homogeneous across the entire cross-section of the molten glass at each forehearth outlet. The forehearth sections described below contribute to this.

[0091] Each forehearth 9, 10 consists of several sections, with a forehearth section having, for example, a total length of 1 m to 10 m.

[0092] The following exemplary embodiments of preheating sections shown in Figures 2 to 29 all feature groups of two resistance heating elements each. As explained above, a single resistance heating element or more than two resistance heating elements can be assigned to a single radiant body.

[0093] Fig. 2 shows a first embodiment of a forehearth section 20 with a U-shaped channel 23 and a superstructure 25 arranged above it. This channel 23 forms the glass contact material, which consists, for example, of zirconium mullite, corundum, oc- and β-alumina, or AZS. The insulation of the channel 23 is formed by an outer section 22 made of thermally insulating material, for example, lightweight silica and / or lightweight refractory brick, mortar. The channel 23 is enclosed by the outer section. The flow of molten glass 30 flows in the channel 23 in the direction indicated by the arrow 31 and has a center of flow 32 (shown hatched) as well as outer areas 33. The superstructure 25 has two side sections 26 and a central section (roof section) 27.The central section 27 has two downward-projecting protrusions 28 extending in the direction of flow, which define three sections in the heated space 35 below: the central space section and the heating sections formed laterally by the central space section. For clarity, these sections are not labeled in Fig. 2; they are explained below with reference to the second embodiment and Fig. 3. Each heating section contains a series of U-shaped groups of resistance heating elements 40, which project downwards from the central section 27 of the superstructure 25 into the space 35. Each group comprises two resistance heating elements 40 arranged side by side in a line in the transverse direction (see arrow 43) such that they are aligned along the transverse direction. The transverse direction is orthogonal to theEach resistance heating element 40 has a U-shaped resistance section 41 at its lower end, which has a smaller diameter than the areas above it. As described above, this generates the heat energy for heating the forehearth section in the respective resistance section 41 when a suitable voltage is supplied. A boat-shaped radiant body 45 is arranged between each group of resistance heating elements 40 and the surface of the molten glass 30, with each radiant body 45 projecting away from the respective side section 26 and into the space 35. Since a series of groups of resistance heating elements 40 extending in the direction of flow is arranged in each heating section, a series of radiant bodies 45 extending in the direction of flow is provided in each heating section. In the figure shown in Fig.In the embodiment shown in Figure 2, the resistance heating elements 40 are arranged at a distance from the respective heating element in a direction perpendicular to the surface of the molten glass. However, the arrangement is such that a side wall 46, which surrounds the heating element 45 in a U-shape and includes a recess 47, surrounds the resistance heating elements when projected onto the plane of the surface of the molten glass. This can also be seen analogously for the third embodiment of a forehearth section in Figure 4.

[0094] The heat energy generated by the resistance sections 41 of the resistance heating elements 40 is largely transferred to the underlying radiant bodies 45, which consist, for example, of ceramics containing aluminum oxide, zirconium oxide, silicon oxide, or chromium oxide, and are thereby heated. A portion of the heat energy generated by the resistance sections 41 also directly heats the outer areas 33 of the molten glass 30 through the space between adjacent radiant bodies 45 in a row. The radiant bodies 45 then transfer their heat energy to the molten glass 30 below, primarily to the outer areas 33. Furthermore, the boat shape of the radiant bodies 45 allows for the reliable collection of decomposition products that may arise due to the degradation of the resistance heating elements 40, as well as a permanently dimensionally stable arrangement of the radiant bodies 45 during operation of the forehearth section 20, as shown in Fig.Figure 2 shows that a central section of space 35 remains free to allow cooling of the molten glass 30 above the center of the stream 32. As will also be shown in some subsequent embodiments, the jet bodies 45 are designed to be interchangeable, so that they can be replaced easily and cost-effectively if necessary.

[0095] The exemplary embodiments of pre-hearth sections described below have a fundamentally similar structure to the first exemplary embodiment of a pre-hearth section 20 shown in Fig. 2. Therefore, reference is made to the explanations above. Differences between the exemplary embodiments are discussed below. The same reference numerals denote the same elements; reference is made to the explanation of the preceding embodiments in this regard.

[0096] The reference numerals of the elements of the second embodiment of the fore-hearth section 50 differ from those of the first embodiment by a value of 30. Reference numerals that differ from each other by exactly 30 thus denote identical elements, and reference is made to the explanations of the first embodiment. The second embodiment of a fore-hearth section 50, shown in Figures 3 to 7, has resistance heating elements 70 that project into the recess 77 of the radiant body 75. This allows a larger portion of the heat energy generated by the resistance section 71 of the resistance heating element 70 to be transferred to the radiant body 75 than in the first embodiment. In the fore-hearth section 50, a cooling channel 59 with a cooling plate 59a is also provided in the superstructure 55, through which cooling air flows and cools the cooling plate 59a. This results in indirect air cooling of the central section 66 of room 65.The free central space 66 of chamber 65 allows for the cooling of the molten glass 60 in the central area. The height of the glass level HG (see Fig. 3) is, for example, 150 mm, and the width BG of the molten glass 60 (see Fig. 3) in the channel 51 is, for example, 750 mm. In contrast, the resistance heating elements 70 heat the heating sections 67 of chamber 65 via the radiators 75. In the two upper radiators 75 of Fig. 4, it can be seen that the resistance sections 71 of the resistance heating elements 70 of a group, when projected onto the plane of the molten glass 60, lie in the area defined by an inner upper boundary line 78 (marked with a dashed line) of the side wall 76 of the associated radiator. Furthermore, it is particularly evident from Fig.Figures 3 and 4 show that in each heating section 67 of the chamber 65, a first resistance heating element 70 is located closer to the central section, and a second resistance heating element 70 is located closer to the side section 56 of the superstructure. The respective second resistance heating element 70 is also located above a step formed by the trough 51 (or alternatively by a side section of the superstructure) and is only used intermittently during operation, for example, during preheating or emergency phases. In contrast, the first resistance heating element 70, located further centrally, is primarily used during the operation of the pre-hearth section 50. Figure 7 also shows how the radiant elements 75 can be replaced.A replacement radiant body 75 can be pulled out laterally from the respective side section 56 of the superstructure 55 and a new radiant body 75 can be pushed in, after the associated resistance heating elements 70 have been moved upwards (vertically) so that they no longer protrude into the respective recess 77 of the radiant body 75 and thus a horizontal movement of the respective radiant body is possible.

[0097] The following are some exemplary dimensions of the elements of the pre-cooker section 50, which can be used in the pre-cooker section 50 according to the second embodiment and, with the modifications described below, also in other embodiments. The dimensions of all radiant elements 75 and resistance heating elements 70 in a pre-cooker section are generally identical. The overall length L (see Fig. 4) of the radiant element 75 can, for example, be 250 mm. It projects, for example, with a front end facing the central section, with a length U (see Fig. 4, also referred to as the projection) of 100 mm into the space 65. The radiant element 75 also has, for example, a width B of 120 mm and a wall thickness d of 25 mm. The distance A between adjacent beam bodies 75 in a row is, for example, 200 mm (see Fig. 4), where the distance is relative to the respective center lines (see dashed lines in Fig.4) the radiator body 75 is measured. The height H (see Fig. 6) of the side wall 76 is, for example, 80 mm. The recess 77 has a depth T of, for example, 60 mm (see Fig. 5). The length LV of the recess is, for example, 180 mm, and the width BV of the recess is, for example, 80 mm (see Fig. 4). With regard to the resistance heating element 70, the length LW of the resistance section 71 in the vertical direction (perpendicular to the surface of the molten glass) can be, for example, 220 mm (see Fig. 5). The radius of curvature of the U-shape at the lower end of the resistance heating element 70 or the resistance section 71 can be, for example, 45 mm, with the thickness of the resistance section being, for example, 9 mm.

[0098] In the third embodiment of a pre-hearth section 80 shown in Figures 8 to 10, the radiant body 105 has a higher side wall 106, which surrounds the recess 107. It has, for example, a height H1 of 140 mm (see Figure 8). The width B1 of the radiant body 105 is, for example, 85 mm (see Figure 10), and the length LW1 of the resistance section 71 of the resistance heating element 70 is, for example, 160 mm (see Figure 9). This results in better heating of the radiant body 105 by the resistance heating element 70, and the heating of the molten glass in the heating section 67 is achieved almost exclusively by indirect heating via the radiant body 105.

[0099] In the fourth embodiment of a pre-hearth section 110 according to Figures 11 to 13, the resistance section 71 of the resistance heating elements 70 is surrounded along its entire length in the vertical direction (direction perpendicular to the surface of the molten glass) by the recess 137 and the side wall 136 of the radiant body 135. As explained above, this increases the service life of the resistance heating elements 70. The side wall 136 of the radiant body 135 is designed such that it extends to the central section (roof section) of the superstructure and thereby shields the interior of the radiant body 135, i.e., the recess 137, from the atmosphere of the chamber 65. The height H2 of the side wall 136 of the radiant body 135 is, for example, 250 mm and the width B2 of the radiant body 135 is, for example, 85 mm (see Figures 11 and 12). This leads to a further increase in the service life of the resistance heating elements 70. Fig.Figure 13 shows that a jet body 135 can also be replaced in such a design analogous to the second embodiment of the forehearth section.

[0100] The fifth embodiment of a forehearth section 140, shown in Fig. 14, has a radiant body 165 which, in cross-section at its base, is more rounded than the radiant body 75 of the second embodiment. The side wall 166 has a height H3 of 100 mm and a width B3 of 85 mm and surrounds the recess 167. The illustrated shape of the radiant body 165 results in a high proportion of direct radiation onto the surface of the molten glass 60 by the resistance heating element 70, which can be advantageous in some cases.

[0101] The sixth and seventh embodiments of a pre-hearth section 170, 200 shown in Figures 15 to 19 have resistance heating elements 190, 220 whose U-shape does not extend transversely perpendicular to the flow direction (as in the first five embodiments of a pre-hearth section 20, 50, 80, 110, 140), but rather in the direction of the flow direction. The two resistance heating elements 190, 220 with resistance sections 191, 221 of a group are also arranged such that they run parallel. This has the advantage that the heating element can be made shorter, so that the heating element 195 is more compact and heats the respective outer area of ​​the molten glass more intensively. Accordingly, the radiant bodies 195 and the recesses 197, 227 of the radiant bodies 195, which accommodate the resistance heating elements 190, 220, are designed to be somewhat wider in the direction of flow. For example, the radiant bodies 195 have a width B4 of 120 mm (see Fig. 17).The height H4 of the side wall 196 is, for example, 80 mm (see Fig. 16). In the sixth embodiment of a fore-hearth section 170, the resistance heating elements 190 of a group are spaced further apart than the resistance heating elements 220 of the seventh embodiment of a fore-hearth section 200. A smaller spacing of the resistance heating elements 220 can be advantageous if they are to be provided with a common terminal block, resulting in material savings. Conversely, the resistance heating elements 190 that are spaced further apart offer advantages in terms of their service life. In this case, however, the resistance heating elements 190 and 220 located closer to the side section 56 of the superstructure 55 are positioned above the step formed by the channel 51 (alternatively, above a step in the side section of the superstructure).

[0102] In the eighth embodiment of a forehearth section 230 shown in Fig. 20, the glass melt 60 has a width (perpendicular to the flow direction) of 500 mm. Compared to the second embodiment of a forehearth section 50, this embodiment has a longer jet body 225 that projects further into the space 65. It can, for example, have a total length L5 of 320 mm (see Fig. 20). In particular, the jet body projects beyond the lower end of the two protrusions 28 extending in the flow direction into the central section 66 of the free space 65.

[0103] The ninth embodiment of a forehearth section 260 shown in Fig. 21 corresponds to the second embodiment of a forehearth section 50, except that the superstructure 55, 265 is designed differently. The central section 267 of the superstructure 265 of the forehearth section 260 has no indirect cooling and no protrusion; rather, it runs essentially straight with small lateral, downward-sloping inclines towards the side section 266. The tenth embodiment of a forehearth section 290 shown in Fig. 22 has a corresponding superstructure design and otherwise corresponds to the sixth embodiment of a forehearth section 170 shown in Figs. 15 to 17. The same applies to the eleventh embodiment of a pre-heating section 320 shown in Fig. 23, which corresponds to the seventh embodiment of a pre-heating section 200 shown in Figs. 18 and 19. The same applies to the one shown in Fig.24 shows the twelfth embodiment of a fore-hearth section 350, which corresponds to the eighth embodiment of a fore-hearth section 230 shown in Fig. 20.

[0104] A thirteenth embodiment of a forehearth section 380 corresponds in its construction to the second embodiment of a forehearth section 50 shown in Figures 3 to 7. However, each jet body 405 has a nose-shaped projection 408 at its first end, which is held in a corresponding, continuous opening 388a of the protrusion 388 of the central section 387 of the superstructure 385. This provides additional fixation of the jet body 405 and counteracts any lowering of the jet body 405 during the operation of the forehearth section 380. The same applies analogously to the fourteenth and fifteenth embodiments of a pre-heating section 410, 440 (see Fig. 27, 28 and Fig. 29 respectively), which correspond to the sixth embodiment shown in Fig. 15 to 17 and the seventh embodiment shown in Fig. 18 and 19 of a pre-heating section 170, 200.Here too, the radiating body 435 has a nose-shaped projection 438 at its first end, which is held with the same effect in a corresponding, continuous opening 388a of the protrusion 388 of the central section 387.

[0105] In the embodiments of pre-hearth sections 470, 500, and 530 shown in Figures 30 to 32, a single heating coil candle is used as the resistance heating element 490 instead of a group of two resistance heating elements arranged above the respective radiant body. In such a heating coil candle, the coils are twisted together so that the resistance heating element 490 has the overall shape of a candle. Each resistance heating element 490 has a resistance section 491 which, when projected onto the plane of the glass melt surface, is located in the area enclosed by the upper inner boundary line of the side wall of the radiant body. The resistance section has, for example, a length LW6 of 120 mm (see Figure 30). The resistance heating elements 490 also project transversely (parallel to the radiant bodies) into the space 65 and are attached in the respective side section 56, 266 of the superstructure 55, 265.Otherwise, the sixteenth embodiment of a pre-cooker section 470 corresponds to the second embodiment of a pre-cooker section 50, the seventeenth embodiment of a pre-cooker section 500 to the eighth embodiment of a pre-cooker section 230, and the eighteenth embodiment of a pre-cooker section 530 to the twelfth embodiment of a pre-cooker section 350. In the embodiments of pre-cooker sections 560 and 590 shown in Figures 33 to 34, a single, rod-shaped resistance heating element 580 is used instead of a group of two resistance heating elements arranged above the respective radiant body. The rod-shaped resistance heating element 580 extends horizontally (i.e., in the transverse direction) such that it covers the entire width of the pre-cooker section 560 or 590. It has, for example, a length of 1200 mm. The resistance heating element 580 has two resistance sections 581, which e.g.Each has a length LW7 of 120 mm (see Fig. 34) and is located in two opposing heating sections 67 of the space 65 of the forehearth section 560, 590 and, when projected onto the plane of the glass melt surface, is arranged in the area enclosed by the upper inner edge line of the side wall of the radiant body. The resistance heating element 580 is attached in the opposing side sections 56, 266 of the superstructure 55, 265. Otherwise, the nineteenth embodiment of a forehearth section 560 corresponds to the second embodiment of a forehearth section 50, and the twentieth embodiment of a forehearth section 590 corresponds to the twelfth embodiment of a forehearth section 350.

[0106] In the embodiments of pre-hearth sections 620 and 650 shown in Figures 33 to 34, a single, egg-shaped resistance heating element 640 is used instead of a group of two resistance heating elements arranged above the respective radiant body. Here, the egg-shaped resistance heating element runs vertically (i.e., perpendicular to the surface of the molten glass) such that its lower end extends into the recess of the radiant body 75. The resistance heating element 640 has a resistive section 641 which, when projected onto the plane of the molten glass surface, is located in the area enclosed by the upper inner boundary line of the side wall of the radiant body. The resistance heating element 640 has essentially the same structure as the resistance heating element 490, which was described above in connection with Figures 30 to 32.The resistance heating element 640 is attached to the central section (roof section) 57, 267 of the superstructure 55, 265. Otherwise, the twenty-first embodiment of a fore-hearth section 620 corresponds to the second embodiment of a fore-hearth section 50, and the twenty-second embodiment of a fore-hearth section 650 corresponds to the ninth embodiment of a fore-hearth section 260.

[0107] Finally, the embodiments shown in Figures 37 to 39 illustrate variants of pre-cooker sections in which additional heating is provided by means of gas burners 79. The twenty-third embodiment of a pre-cooker section 680 corresponds to the fifth embodiment of a pre-cooker section 140 shown in Figure 14. In each heating section 67, a gas burner 79 is arranged between two adjacent radiant bodies 165 with associated resistance heating elements 70 in the direction of flow, wherein the gas burner 79 is arranged approximately at the level of the lower end of the resistance heating elements 70 or approximately centrally with respect to the vertical extent of the radiant bodies 165. In the direction of flow (horizontal direction), the gas burners 79 are also arranged centrally between two adjacent groups of resistance heating elements 70. Alternatively, in the twenty-fourth embodiment of a pre-cooker section shown in Figure 14, the gas burners 79 are arranged in the same way as the five embodiments shown in Figure 14.In the fore-hearth section 710 shown in Figure 39, three gas burners 79 are arranged between two adjacent radiant elements 165 with associated resistance heating elements 70 in the flow direction. As can be seen in Figure 39, the three gas burners are arranged approximately equidistantly between adjacent groups of resistance heating elements 70 in the flow direction (horizontal direction). The gas burners 79 allow hybrid operation of the fore-hearth sections 680 and 710 with the advantages described above through the use of the radiant elements 165, which makes the heating more variable. The ceramic channels of the gas burners 79, shown in Figures 37 to 39, have, for example, a diameter of 6 mm. The gas burners are implemented, for example, as fore-cooker burner batteries (mixed gas burners, e.g., mixed gas of natural gas and air), whereby the gas mixture reaches the respective channel by means of a metal pipe running along the outside of the fore-cooker section.In addition, each channel has a nozzle for the mixed gas, which ignites in the channel.

Claims

Paternal sayings 1. Device for guiding a glass melt with a channel in which the molten glass is guided along a flow direction from an inlet to an outlet, wherein the channel is covered with a superstructure, the superstructure extending above the surface of the molten glass and enclosing a space above the molten glass along the channel, wherein in two opposing heating sections of the space above the molten glass, which are located above the two outer areas of the molten glass extending in the direction of flow, a plurality of resistance heating elements are arranged in a row, wherein the resistance heating elements project into the respective heating section and each introduce thermal energy into the device for heating the molten glass by means of a resistance section, wherein the resistance heating elements of a row are arranged individually or in groups of at least two resistance heating elements one behind the other along the direction of flow, wherein the at least two resistance heating elements of a group lie next to each other in a transverse direction perpendicular or oblique to the direction of flow, wherein in each heating section a plurality of radiant elements are provided, which are arranged one behind the other and spaced apart from each other along the direction of flow, project from the respective side section of the superstructure in the transverse direction and extend into the space in such a way that a central space section between the two opposing heating sections remains free, wherein each radiant element has an elongated boat shape with a depression, wherein the depression is surrounded at a first end opposite the respective side section of the superstructure and on at least two sides enclosing the first end by a side wall which forms an inner upper edge line, wherein each radiant body is arranged between a single resistance heating element or a group of resistance heating elements of the respective series and the surface of the glass melt such that the recess faces the associated resistance heating element(s), that an area is enclosed by the inner upper edge line of the side wall of the respective radiant body when projected onto the plane of the surface of the glass melt, and that within this area there is a projection of the respective resistance section(s) of the associated resistance heating element(s) into the same plane, wherein each radiant body absorbs at least part of the heat energy generated by the associated resistance heating element(s) and transfers it to the underlying molten glass via its surface facing the molten glass.

2. Device according to claim 1, characterized in that a lower end section of the resistance section of the associated single resistance heating element or of the at least two resistance heating elements of the associated group protrude into the recess of the respective radiant body.

3. Device according to claim 1, characterized in that a lower end of the associated single resistance heating element or each lower end of the at least two resistance heating elements of the associated group has a distance from the upper edge of the respective radiant body which is a maximum of 200 mm.

4. Device according to claim 2, characterized in that the resistance section of the associated single resistance heating element or of the at least two resistance heating elements of the associated group has essentially the same distance to the inner surfaces of the side wall of the radiant body in the area of ​​the recess.

5. Device according to one of the preceding claims, characterized in that the plurality of beam bodies is designed in such a way that it is interchangeable.

6. Device according to one of the preceding claims, characterized in that the total length of the beam body in the transverse direction is at least 100 mm.

7. Device according to one of the preceding claims, characterized in that the width of the jet body in the direction of flow is at least 50 mm.

8. Device according to one of the preceding claims, characterized in that the width of the recess of the jet body in the direction of flow is at least 20 mm and / or the length of the recess of the jet body is at least 60 mm.

9. Device according to one of the preceding claims, characterized in that the height of the side wall of the jet body is at least 30 mm and / or the wall thickness of the side wall of the jet body is at least 3 mm.

10. Device according to one of the preceding claims, characterized in that the height of the side wall of the radiant body and the arrangement of the radiant body are designed such that the resistance section of the associated single resistance heating element or the respective resistance sections of the at least two resistance heating elements of the associated group is enclosed in its entire height by the side wall of the radiant body.

11. Device according to one of the preceding claims, characterized in that additional heat energy is introduced into the two opposing heating sections. the room is cooled by means of a large number of burners that burn a flammable gas and are arranged in the respective side section of the superstructure and / or that the central room section is cooled by means of indirect air cooling.

12. Device according to one of the preceding claims, characterized in that the resistance heating elements are made on the basis of MoSi2 or on the basis of SiC.

13. Device according to one of the preceding claims, characterized in that the beam body has a nose-shaped projection at its end furthest from the side section of the superstructure, which projects into a corresponding recess in the roof section of the superstructure, wherein the recess in the roof section supports the associated beam body in the installed state.

14. Device according to one of the preceding claims, characterized in that the nose-shaped projection has a beveled underside.

15. System for melting and transporting glass with a glass melting tank and optionally a working tank arranged downstream in the global flow direction of the glass, wherein the raw materials for glass production and optionally the glass cullet are completely melted in the glass melting tank and optionally in the working tank, wherein the molten glass, after exiting the glass melting tank, enters one or more devices for guiding a molten glass according to one of the preceding claims, wherein each device for guiding a molten glass guides it to a further device for guiding a molten glass or to a forming device.

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