Glass melting tank furnace

Abstract

The invention relates to a tank furnace for all-electrically heating a glass melt arranged in the interior of the tank furnace, having a stepped bottom, a plurality of electrodes and side walls, which can achieve yields of 80 t / day to 450 t / day and good glass quality. Above the raised bottom section, the hot cell sides of the side walls form an at least pentagonal polygon, circle or ellipse in a horizontal cross-section. The bottom has a raised bottom section which surrounds at least 70% of the circumference of the tank furnace interior and a central homogenized bottom section which is surrounded by the raised bottom section and deeper than the raised bottom section, wherein the raised bottom section extends transversely from the hot chamber side of the side wall towards the tank furnace interior and has a width greater than or equal to 0.25 * D (D is the mean diameter), and wherein a transition wall extending perpendicularly to the surface of the glass melt is formed at the transition from the raised bottom section to the homogenized bottom section, wherein a first group of the plurality of electrodes protrudes into the glass melt in a region adjacent to the side wall, and a second group of the plurality of electrodes is arranged in a region adjacent to the transition wall in the raised bottom section.

Description

[0001] The invention relates to a glass melting tank furnace for fully electrically heating a glass melt in production operation, a glass melting plant and a method for producing a glass melting tank furnace.

[0002] A tank furnace for preparing a glass melt (glass melting tank furnace) generally has a bottom and side walls surrounding the inner space of the tank furnace. In the production operation state, the glass melt is arranged in the inner space of the tank furnace, and in the inner space of the tank furnace, it is defined by the bottom at the bottom and by the walls at the sides. In addition, the inner space of the tank furnace is generally at least partially covered by a roof at the top in order to reduce the loss of heat energy and / or the emission of exhaust gas and dust. During the homogenization process, the glass melt flows in the interior of the tank furnace along a flow direction from the melting zone where the raw material mixture and possible scrap are fed into the interior of the tank furnace to at least one outlet opening, through which the molten glass is drawn. The drawn molten glass can be used, for example, to produce container glass, flat glass, rolled glass, fiber glass, glass fiber, household glass or industrial glass.

[0003] So-called cold-top tank furnaces usually have a complete cover of unmelted raw materials (raw material mixture and / or scrap) arranged above the glass melt, whose temperature is significantly lower than that of the glass melt and is therefore called "cold". The "cold" cover has the known advantages that it is thermally insulating and serves as a resource-saving condensate catcher. In cold-top technology, the glass generally flows in a vertical direction, i.e. from top to bottom, and is pulled off in the region of the bottom or laterally from the bottom.

[0004] Fully electrically heated glass melting tank furnaces are known and are nowadays used in particular for smaller glass production (conveying capacity / melting capacity / tonnage), which for good quality glass are in the range of a maximum of 250 tons of molten glass / day. From document US 3,520,979, a glass melting tank furnace utilizing electrical heating is known, wherein the interior space of the tank furnace has the shape of a complete six-sided prism, wherein electrodes extend from the side walls into the molten glass. The glass melting tank furnace shown in document DE 34 05 273 C2 also has the same shape of the interior space of the tank furnace, wherein in this variant the electrodes are implemented as top electrodes. Document US 3,885,945 discloses an electrically heated rectangular tank furnace interior space, wherein the flow direction of the molten glass is horizontal. Today, glass melting tank furnaces utilizing all-electric heating mainly work according to the cold top principle, i.e. a cover of a "cold" raw material mixture and / or scrap is arranged on the glass bath.

[0005] From document US Pat. No. 3,683,093, an electrically heated glass melting tank furnace is known, which has four parallel electrode rows, wherein each electrode is arranged on a raised bottom section and extends upward from the bottom section into the glass melt. Between two outer electrode rows, feed channels are arranged respectively, extending parallel to the two outer electrode rows, which feed channels are connected to collecting channels arranged between two central electrode rows. The collecting channels also extend parallel to the electrode rows and lead directly to the outlet of the glass melting tank furnace, wherein the collecting channels have the same width as the outlet.

[0006] Documents JP S60-24055 B2 and JP S61-222928 A also describe electrically heated glass melting tank furnaces, the interior of which is designed such that the glass melt is arranged in a wider upper section (with a larger diameter) and a narrower section (with a smaller diameter) located below it. The glass melt can be heated in both sections, that is, even in the narrower section, by means of electrodes.

[0007] The importance of climate protection and the associated societal pressure on energy-intensive processes used in the glass industry are increasing day by day. The processes currently available for obtaining renewable (so-called "green") energy mainly produce electrical energy, the direct use of which makes energetic sense. High efficiencies can be achieved by directly utilizing electrical energy for melting the glass, for example in the form of heating with the aid of electrodes based on the Joule effect. In contrast, the losses are much greater overall when the regeneratively generated electrical energy is converted into another energy carrier (e.g. hydrogen) and heated by, for example, burning this energy carrier. Therefore, the intensification of the use of direct electrical heating of glass melting tanks is of great interest, in particular for glass melting tanks that are intended to achieve higher throughput capacities.

[0008] Other factors that influence the further development of glass melting tank technology are the desired glass quality and the size of the glass melting tank. In many cases, the glass quality should be high, that is, the bubble density in the final product should be less than 60 small bubbles per 100 grams of glass. On the other hand, for the space required for the glass melting tank, the daily output should be increased by a larger unit within a reasonable cost.

[0009] The object of the present invention is therefore to provide a compact glass melting tank furnace which can be fully electrically heated in production operation, provides good glass quality and is suitable for medium to large glass production. The object is also to provide a cost-effective and simple method for manufacturing such a glass melting tank furnace.

[0010] This object is achieved by a glass melting tank furnace having the features of claim 1 and a method for producing the glass melting tank furnace having the features of claim 14. This object is also achieved by a glass melting plant having the features of claim 13.

[0011] In particular, the above-mentioned purpose is achieved by a glass melting tank furnace for fully electrically heating a glass melt arranged in an inner space of the tank furnace under production operation conditions, the glass melting tank furnace having a stepped bottom and side walls, wherein the inner space of the tank furnace is defined downward by the bottom, and the side walls surround the inner space of the tank furnace on the sides, wherein under production operation conditions, the glass melt is arranged in the inner space of the tank furnace, wherein the hot chamber side of the side wall above the raised bottom section forms a polygon of at least five sides (for example, a polygon of at least six sides), a circle or an ellipse in a horizontal cross section, wherein the bottom has a raised bottom section surrounding at least 70% of the circumference of the inner space of the tank furnace, preferably a raised bottom section surrounding at least 80% of the circumference of the inner space of the tank furnace, and a homogenizing bottom section having a center surrounded by the raised bottom section and deeper than the raised bottom section, wherein the raised bottom section extends laterally from the hot chamber side of the side wall toward the inner space of the tank furnace and has a radius greater than or equal to 100 m. A width B of 0.25×D, where D is the average diameter of the inner space of the tank furnace above the raised bottom section, wherein a transition wall extending vertically or almost vertically relative to the surface of the glass melt is formed at the transition from the raised bottom section to the homogenizing bottom section, wherein the glass melting tank furnace has a plurality of electrodes for heating the glass melt in a production operation state, wherein in the production operation state, the surface of the glass melt is located above the raised bottom section, and a first group of the plurality of electrodes is in an area adjacent to the side wall above the raised bottom section or extends into the glass melt from the raised bottom section, and a second group of the plurality of electrodes is arranged in an area adjacent to the transition wall in the raised bottom section and extends into the glass melt from the raised bottom section, so that for the glass melt in the inner space of the tank furnace, a melting and fining chamber is formed above the level of the raised bottom section, and a homogenizing chamber is formed below this level, wherein the homogenizing chamber is surrounded by the transition wall on the side and by the homogenizing bottom section on the bottom. (The specification 0.25×D involves the multiplication of the numbers 0.25 and D, and multiplication operations are expressed in a similar manner below.)

[0012] The glass melting tank furnace according to the present invention has a tank furnace interior space, which is defined by the bottom at the bottom and by walls made of refractory materials along the maximum range of the glass melting tank furnace on the side. The side walls include all the outermost side walls of the glass melting tank furnace, but do not include the transition wall arranged between the raised bottom section and the homogenized bottom section. In the production operation state, the glass melt is arranged in the tank furnace interior space. According to the present invention, the hot chamber side of the side wall facing the glass melt above the raised bottom section has a shape of at least five-sided polygon (i.e. not rectangular), circular or elliptical in horizontal section, or a shape approximating these geometric shapes. Here, "essentially" means that the hot chamber side of the side wall can have recesses and steps, which are not taken into account when considering the general shape of these faces. The side wall, in particular, takes this shape in the vertical section of the glass melting tank furnace, which is located in the area of ​​the glass level depth and the glass melt cover above the raised bottom section. Importantly, from a macroscopic perspective / overall, the flow direction of the glass melt in production operation is essentially from top to bottom, i.e., from the surface of the glass melt to the bottom of the glass melting tank furnace (more precisely, the bottom in the area of ​​the homogenizing bottom section).

[0013] The state of the glass melting tank furnace "under production operation" means that flat glass, insulating glass, fiber glass or special glass is produced using glass melted in the glass melting tank furnace and drawn through at least one outlet opening. This is different from operations in which glass production is slowly accelerated or decelerated (heated up or cooled down), for example during maintenance phases or before or after commissioning.

[0014] With respect to the horizontal cross section above the raised bottom section, the hot chamber side or transition wall of the side wall may have a curved shape (i.e., the shape of a (partial) cylindrical side surface) or extend straight in sections, i.e., form the shape of a (partial) prism side surface. In particular, the side wall above the raised bottom section substantially has the shape of a polygon with at least five sides, a circle or an ellipse in the horizontal cross section, or a shape approximating these geometric shapes.

[0015] The bottom of the glass melting tank kiln has at least one step, and is therefore referred to as "stepped" above. Here, the step is formed by a raised bottom section, a transition wall and a homogenized bottom section, wherein the step extends along at least 70% of the circumference of the inner space of the tank kiln (i.e., on the side wall). Therefore, the bottom of the glass melting tank kiln has a homogenized bottom section surrounded by a raised bottom section. It is very advantageous for the glass quality that the step extends along most of the circumference of the inner space of the tank kiln (e.g., at least 80% of the circumference), or extends along the entire circumference of the inner space of the tank kiln, thereby surrounding the entire homogenized bottom section. In the latter case, the step is uninterrupted. The step can be formed as a single uninterrupted step, or can be formed as two or more sections extending in the circumferential direction, especially when the glass melting tank kiln has more than one outlet opening for pulling out molten glass. For example, the step can be interrupted / divided by a channel leading to the outlet opening, which connects the homogenization chamber to the outlet opening further outward.

[0016] Viewed in three dimensions, the internal space of the tank furnace essentially has the shape of two three-dimensionally arranged spatial shapes stacked on top of each other, where each of these two spaces can have the shape of a prism (horizontal cross-section corresponding to a polygon) or a cylinder (horizontal cross-section corresponding to a circle or an ellipse), or a shape approximating these shapes. Here, the shapes of these spaces can be combined arbitrarily, and thus can be adapted to various other situations of the glass melting tank furnace. For example, the melting and clarification chamber can have the shape of a prism, while the homogenization chamber can have the shape of a cylinder, or vice versa. Combinations of similar shapes (cylinder - cylinder or prism - prism) are also possible. The side walls and transition walls are accordingly formed. When making this consideration (dividing the internal space of the tank furnace into two spaces), the (multiple) outlet openings and the area of the channel(s) that may be located upstream of the (multiple) outlet openings in the flow direction of the glass melt are not considered. The space (or volume) formed by the internal space of the tank furnace above the raised bottom section is the melting and clarification chamber and has an average diameter D (measured from the hot chamber side of the side wall). Thus, the raised bottom section defines the level of the melting and clarification chamber formed by the internal space of the tank furnace. In one embodiment, the average diameter D of the internal space of the tank furnace above the raised bottom section (i.e., the average diameter of the melting and clarification chamber) is at least 5 m. For example, the maximum average diameter D of the internal space of the tank furnace above the raised bottom section can be 16 m. The space (or volume) formed for the glass melt directly below the level of the raised bottom section is the homogenization chamber, which is bounded laterally by the transition wall, upward by the melting and clarification chamber, and downward by the homogenization bottom section, and the upper end of the homogenization chamber is approximately at the height of the raised bottom section. The homogenization chamber has an average diameter d, where d < D / 2. The diameter d of the homogenization chamber is significantly smaller than the diameter of the melting and clarification chamber (d = D - 2×B, where B ≥ 0.25×D). In one embodiment, the average diameter d of the homogenization chamber is at least 1.6 m and at most 8 m. In other words, the raised bottom section extends laterally from the hot chamber side of the side wall towards the internal space of the tank furnace and has a width B greater than or equal to 0.25×D = D / 4. In one embodiment, the width B is less than or equal to D / 3 in order to obtain a volume sufficient for good homogenization of the glass melt through a sufficiently large lateral extent of the homogenization chamber.

[0017] The above definition also includes that the two spaces (melting and refining chamber and homogenizing chamber) are arranged essentially concentrically, i.e. the two vertically extending axes of these spaces are superimposed or parallel, wherein in the latter case the axes have only a small distance in the horizontal direction, i.e. a distance of at most 0.5 m. The average diameter d is determined as the average diameter in the region of the homogenizing chamber, i.e. the average diameter of the glass melting tank furnace below the raised bottom section. In addition, the homogenizing chamber is arranged directly below the melting and refining chamber, i.e. directly below the melting and refining chamber. The raw materials are melted and refined in the melting and refining chamber after they are preferably placed from above and then enter the homogenizing chamber located directly below.

[0018] The homogenization chamber can also have a circular, elliptical or at least three-sided polygonal shape, for example at least five-sided polygonal or at least six-sided polygonal shape in horizontal cross section. This means that, depending on the shape of the homogenization chamber, the raised bottom sections may not all have the same width in the horizontal direction. This is caused by the shape of the melting and refining chamber and the homogenization chamber.

[0019] Each of the two chambers can take the form of a rotationally symmetrical body, wherein rotational symmetry is understood to mean that by rotating a certain predetermined angle around the longitudinal axis, the corresponding body will be reflected onto itself. In one embodiment, the rotationally symmetrical body is a substantially straight body, because a chamber in the form of a straight body is less expensive when realizing such a glass melting tank furnace.

[0020] In the vertical direction, the interior space of the tank furnace has a predetermined height, wherein the height is measured from the bottom of the homogenizing bottom section to the upper edge of the side wall. In one embodiment, the vertical height of the interior space of the tank furnace is a maximum of 3.5 m, because a deeper tank furnace would endanger the operational reliability of the device in view of the temperature-related length change behavior of the refractory material forming the side wall and the transition wall and the in vitro static pressure of the glass.

[0021] In one embodiment, the height difference h between the raised bottom section and the homogenizing bottom section is at least 0.5 m. As a result, a sufficiently large homogenizing chamber is provided in the vertical direction and in terms of volume (taking into account the extent in the horizontal direction), so that a good glass quality can be achieved. The mentioned height difference simultaneously forms the vertical height of the homogenizing chamber. The height difference is measured in the vertical direction relative to the surface of the molten glass (irrespective of a possibly inclined design of the transition wall). In one embodiment, the height difference between the raised bottom section and the homogenizing bottom section is a maximum of 2.7 m. When taking into account the height difference h, the flange (Kragen) which can be arranged on the raised bottom section and is described below is not taken into account.

[0022] In the production operation state, the height of the glass melt in the inner space of the tank furnace is also called the glass level depth. Here, the glass level depth only covers the height of the melt, but not the covering composed of cold raw material mixture and / or scraps arranged on the melt. The glass level depth is a value associated with the inner space of the tank furnace of the glass melting tank furnace and can be measured indirectly, for example, by the bath depth in a riser, which is connected to the glass melting tank furnace after the outlet opening and the circulation channel in the flow direction. In the area of ​​the raised bottom section, the glass level depth T can be at least 0.8m and a maximum of 2.7m, while in the area of ​​the homogenized bottom section, the glass level depth can be at least 1.3m and a maximum of 3.2m.

[0023] In one embodiment, the transition wall can extend vertically relative to the surface of the glass melt. Alternatively, the transition wall can extend at a small angle to the vertical line (for example, at a maximum angle of 30° to the vertical line). Here, the inclination of the transition wall can be selected so that the diameter of the homogenization chamber at the top is larger than the diameter at the bottom in the area of ​​the homogenization bottom section, or vice versa. In the simplest embodiment, the surface of the raised bottom section extends parallel to the surface of the glass melt. In one embodiment, the surface of the raised bottom section can extend at an angle, for example, so that the depth of the glass level above the raised bottom section increases radially toward the center of the glass melting tank kiln, that is, the surface of the raised bottom section is inclined downward toward the center of the glass melting tank kiln.

[0024] In the glass melting tank furnace according to the present invention, the electrodes activated and extending into the glass melt in the production operation state are arranged in two groups. In the production operation state, the first group of electrodes are used as top electrodes, bottom electrodes and / or side electrodes in the area adjacent to the side wall, and the second group of electrodes are used as bottom electrodes in the area adjacent to the transition wall. The two groups are located in the area of ​​the bottom section of the projection, that is, in or above the bottom section of the projection. In particular, in one embodiment, the electrodes activated in the production operation state are not arranged in the homogenization chamber. This means that in the production operation state, the glass melt located in the homogenization chamber is not heated. More precisely, the energy input (i.e., heat input) to the glass melt only occurs in the area of ​​the melting and refining chamber located above the level of the bottom section of the projection. The electrodes of the first group and the electrodes of the second group are spaced apart from each other, for example, in the radial direction, wherein the distance between the electrodes is selected so that the distance between the electrodes becomes as large as possible, taking into account the width of the bottom section of the projection and the minimum distance from the side wall in the first group (top electrode and bottom electrode) and the minimum distance from the transition wall. In one embodiment, no further electrodes are provided between the two groups for heating the glass melt in production operation. Alternatively, at least one further electrode group can be provided between the two groups, which supplies thermal energy to the glass melt in production operation, wherein the further group is also arranged in the melting and refining chamber and heats the glass melt above the raised bottom section.

[0025] Compared to earlier solutions using all-electric heating, by forming the interior space of the tank furnace in the above-mentioned stepped shape according to the invention and arranging the electrodes specifically as electrodes close to the side walls (first group of electrodes) and bottom electrodes protruding from the raised bottom section and arranged close to the transition wall (second group of electrodes), a significant increase in the diameter of the glass melting tank furnace can be achieved, thereby achieving a significant increase in the glass production, wherein very good glass quality is achieved at the same time. As shown based on the following example, the glass production is particularly in the range between 80 tons / day and 450 tons / day. This production is achieved in the following way: on the one hand, in the region of the melting and refining chamber above the raised bottom section, due to the two electrode groups arranged there, which are spaced apart from each other and the flow generated thereby in the glass melt, good melting of the raw materials (mixture and / or scraps) preferably placed from above and good refining of the glass melt (i.e., the discharge of bubbles) are achieved. The distance between the electrodes of the first electrode group and the electrodes of the second electrode group causes a strong, easily controllable flow to form in the glass melt in the region of the melting and refining chamber. In particular, the distances of the electrodes of the first group to the nearest electrodes of the second group or to the oppositely arranged electrodes of the second group are approximately equal, so that in the glass melting tank furnace, even in the central region of the glass melt arranged in the melting and refining chamber, corresponding, adequate flow dynamics can be achieved which do not differ much from the flows in the outer regions of the melting and refining chamber (see below for details). Figure 2b and Figure 2c ). In addition, due to the essentially vertical arrangement of the bottom electrode, the flow has a significant vertical component, which is beneficial for good melting and good refining in the melting and refining chamber. In addition, a sufficient volume of the glass melt is available in the homogenization chamber located below the melting and refining chamber, so that the glass melt is homogenized and stabilized to the extent required for good gas quality, i.e., solid raw materials or gas bubbles are prevented from escaping directly into the outlet opening. This is possible in particular because in the production operating state, no energy is input into the homogenization chamber, since the glass melt is not heated here by means of electrodes.

[0026] The above-mentioned dimensions of the melting and refining chamber and the homogenizing chamber (achieved by the dimensions of the raised bottom section, the transition wall and the homogenizing bottom section) and the above-mentioned arrangement of the electrodes on the raised bottom section make it possible to form convection zones rotating in opposite directions (relative to the vertical cross section) in the glass melt between the opposing electrodes in the melting and refining chamber, wherein each convection zone has a larger vertical upward component in the region close to the corresponding electrode and a larger vertical downward component in the central region between the opposing electrodes. Each convection zone has a larger horizontal component in the region near the electrode and between the corresponding adjacent central region. The convection zones in the glass melt are arranged in a manner that the convection zones rotate in opposite directions (relative to the vertical cross section) in opposite directions. Figure 2b and Figure 2c, which are shown by way of example in conjunction with an embodiment and will be explained below. As described above, the convection zone achieves good mixing of the raw materials, which are preferably placed from above, and is conducive to the thorough dissolution of the more difficult to melt components in the raw materials. This convection occurs in the melting and refining chamber. In contrast, in production operation. No energy is input through the electrodes in the homogenizing chamber, so the glass melt has a significantly smaller flow velocity in the homogenizing chamber (for example, at least one order of magnitude smaller), except for the transition section of the homogenizing chamber, which is arranged adjacent to the melting and refining chamber and at the transition to the melting and refining chamber. In this transition section, the glass melt flows at a slightly higher speed. The height of the transition section is not more than 0.25×h measured in the vertical direction from the level of the raised bottom section, for example not more than 0.15×h, wherein the transition section has a smaller height (vertically measured from the level of the raised bottom section) on the side of the homogenizing chamber (i.e., seen in the radial direction) than in the central area. In the main section of the homogenization chamber, which is located below this transition region and occupies the majority of the homogenization chamber, the glass melt is characterized in that, at points in this region, the vertical component of the glass flow velocity (i.e., the average sinking velocity of the glass melt in the direction of the outlet opening) is approximately in the order of magnitude of the floating velocity of the gas bubbles contained in the melt or is less than this floating velocity of the gas bubbles. The main section has a greater height at the side of the homogenization chamber (i.e., seen in the radial direction) than in the central region. Here, the respective sinking velocity and the respective floating-related velocity are related to the respective glass chemistry (i.e., the respective composition of the glass melt or the respective glass type (borosilicate glass, water glass, container glass, fiber glass)). This means that the glass melt is stable in the homogenization chamber as described above, and any bubbles that may still be present are not pulled downwards by the sinking glass melt in the direction of the outlet opening, but are moved upwards into the melting and refining chamber due to the buoyancy of the bubbles. In addition, the size of the vertical height h of the homogenization chamber also has an influence, so that the outlet opening has a sufficient vertical distance from the melting and refining chamber in order to provide sufficient time and volume for the bubbles to rise. In one embodiment, the outlet opening is arranged such that in the new state of the glass melting tank, the upper edge of the outlet opening has a vertical distance of greater than 1 / 2×h from the level of the raised bottom section. The convection zone and the temperatures and flow velocities prevailing in the glass melt are explained in more detail below based on an example and corresponding simulations.

[0027] In order to achieve particularly good results with regard to glass quality, the electrodes of the first group are arranged in particular in the region of the melting and refining chamber such that their distance from the hot chamber side of the side wall (in the horizontal direction) is a maximum of 800 mm.

[0028] The electrodes of the first group can be implemented as top electrodes and / or side electrodes and / or bottom electrodes. As top electrodes, the respective electrodes extend from the surface of the glass melt into the glass melt, as side electrodes, the respective electrodes extend from the side walls into the glass melt, and as bottom electrodes, the respective electrodes extend from the bottom section of the protrusion into the glass melt. For example, the top electrode can have a minimum (horizontal) distance of 150 mm from the side wall, while the bottom electrode can have a minimum (horizontal) distance of 150 mm from the side wall (in each case in relation to the hot cell side of the side wall). The side electrodes can have a distance of a maximum of 2.5 m and / or at least 200 mm from the bottom section of the protrusion, wherein the distance also depends on the depth of the glass level above the bottom section of the protrusion.

[0029] The electrodes of the second group are, for example, embodied as bottom electrodes and have, for example, a minimum distance of 500 mm from the edge where the transition wall of the raised bottom section begins (hereinafter also referred to as the inner edge). Furthermore, these electrodes have a predetermined distance from the electrodes of the first group. Thus, the horizontal diameter of the arrangement formed by the second group of electrodes is greater than the diameter d of the homogenization chamber, for example at least 1 m greater.

[0030] In one embodiment, the electrodes in the respective groups (i.e., in the first group and in the second group) can be evenly distributed / equidistantly arranged along a line extending parallel to the horizontal cross-sectional line of the sidewall (for the first group of electrodes) or the transition wall (for the second group of electrodes). Alternatively, the electrodes of the first group can be arranged into a subgroup of three individual electrodes or three electrode pairs, for example as described below, which have a smaller spacing in the direction along the line. Here, the distance between the two outer electrodes / electrode pairs in the three electrodes / electrode pairs is roughly equivalent to the distance between the middle electrode / electrode pair in the second group and the relative electrode / electrode pair.

[0031] In one embodiment, (when these electrodes are implemented as top electrodes or bottom electrodes) all electrodes in the first group have the same distance (in the horizontal direction) from the side wall, and / or all electrodes in the second group have the same distance (in the horizontal direction) from the transition wall. Alternatively, within the respective group, the distance to the side wall or transition wall may vary, which may also be caused by a specific shape of the side wall or transition wall.

[0032] In order to obtain good glass quality, it is important that the electrodes are arranged so that the volume of the melting and refining chamber is heated as a whole and no dead zones are created. In the dimensions of the glass melting tank furnace according to the invention and the arrangement of the electrodes, such dead zones are avoided. Figure 2b and Figure 2c In the embodiment shown, the convection introduced by the second set of electrodes produces a convection zone extending across the central region of the melting and refining chamber.

[0033] The above-described advantageous spatial arrangement of the electrodes of the first group close to the side wall and of the electrodes of the second group close to the transition wall results in flow dynamics in the melting and / or refining chamber which are particularly uniform in the horizontal direction and can therefore be adjusted relatively stably.

[0034] The internal space of the pool kiln is a space determined for melting the added raw material mixture and / or the supplied scraps, clarifying the glass melt and homogenizing it. As described above, the internal space of the pool kiln can be divided into a melting and clarifying chamber located above and a connected homogenizing chamber located below it. Therefore, the internal space of the pool kiln has a compact shape, and in addition, this shape is easily accessible from the outside. The given shape is usually made by grid bar components composed of refractory materials, which are placed side by side and / or stacked and fastened. Refractory materials are, for example, inorganic, non-metallic materials (ceramics, glass, glass ceramics, mineral fibers), and may include, for example, oxides (silicon oxide, aluminum oxide, magnesium oxide, calcium oxide, zirconium oxide, chromium oxide). In addition, carbon and silicon carbide can also be used as components. For example, fused casting AZS (aluminates, zirconates, silicates, also including oxides of aluminum, zirconium and silicon) is used as material. In addition, the refractory material on the hot chamber side may have at least one coating, which is, for example, made of platinum or a platinum alloy. With or without said coating, the refractory material may consist of one layer, at least two layers with different compositions (eg with different proportions of zirconium) or more than two layers.

[0035] The side walls and transition walls of the glass melting tank furnace, which are respectively facing away from the cold chamber side of the tank furnace interior, can extend substantially parallel to the corresponding hot chamber side. The cold chamber side can be at least partially or completely provided with an insulation layer.

[0036] In one embodiment, a flange of at least 50 mm high and / or at least 50 mm wide can be arranged directly on the transition wall in the region of the raised bottom section. Here, the height is specified as the height above the raised bottom section. The width is the extent of the flange in the horizontal direction. The flange starts from the transition wall and represents a raised structure protruding upward in the vertical direction from the raised bottom section. The end wall (threshold) of the flange opposite to the transition wall is arranged radially more inwardly in the tank furnace interior space than the electrodes of the second group. The flange realizes additional mechanical isolation of the moving zone in the melting and refining chamber and the stable zone in the homogenizing chamber.

[0037] In one embodiment, the glass melting tank furnace is configured to work according to the cold top principle. This means that the raw material mixture and / or the crushed material are fed from above in the direction of the glass melt surface which is preferably completely covered most of the time in the production operation state. In one embodiment, in the production operation state, the diameter or area of ​​the glass melt surface covered with the raw material mixture and / or the crushed material is greater than the diameter d or the cross-sectional area of ​​the homogenization chamber. As described above, in the production operation state, the heating of the glass melt is performed only by means of an electrode extending into the glass melt surface from above (top electrode), an electrode extending into the glass melt from the bottom section of the protrusion (bottom electrode) or an electrode extending into the glass melt from the side wall (side electrode) (more precisely, only extending into the glass melt arranged in the melting and clarification chamber). In addition, at least one burner for fossil heating (for example, for heating the glass melting tank furnace) can be provided, but the burner is not used in the production operation state.

[0038] In one embodiment, the inner space of the tank kiln is covered by a cover on the top, and the cover closes the inner space of the tank kiln in an almost completely dust-tight manner. In other words, the inner space of the tank kiln is closed in a completely dust-tight manner, so that in the production operation state, a negative pressure is formed in the central area of ​​the inner space of the tank kiln located above the glass melt relative to the position around the glass melting tank kiln, and the exhaust gas discharged from the inner space of the tank kiln is released at this position. Therefore, the dust-proof seal realizes that there is actually no dust from the inner space of the tank kiln into the area around the glass melting tank kiln. In addition, the seal can significantly reduce heat loss. In normal operation, the openings for the electrodes and the burners that may exist are closed in a dust-tight manner, and this is not ensured only when the electrodes are replaced. In addition, in the production operation state, the openings for supplying mixtures and / or scraps are closed in an airtight manner. If necessary, an exhaust device (for example, in the side wall) is provided, and the gas generated during melting can be discharged through the exhaust device. The gas is filtered through an appropriate filter (for example, for toxic gases and dust) so that the corresponding environmental regulations are complied with. The exhaust gas is discharged into the environment.

[0039] In one embodiment, the cover is designed as a rotating cover, which has a substantially disc shape, and is preferably designed as a suspended rotating cover. The use of the rotating cover of the above shape enables simple upward covering of the inner space of the tank furnace, thereby avoiding or reducing heat loss and the emission of exhaust gas and / or dust. At the same time, the rotating cover designed to be rotatable by at least 90°, preferably at least 180°, allows the raw material mixture and / or crushed material to be simply, uniformly and easily controlled to be supplied to the glass melt.

[0040] The side walls, transition walls and bottom of the glass melting tank furnace can be at least partially held by means of an external steel support arranged on the cold chamber side. Here, the external steel support supports the side walls, transition walls and bottom (i.e., the raised bottom section and the homogenized bottom section). In addition, the external steel support can have an annular track element on its top side. The corresponding track element is used to support and guide the rotating cover, wherein the rotating cover has at least three corresponding wheels or wheel pairs, which roll along the corresponding track elements.

[0041] In one embodiment, the sealing of the glass melting tank in the area of ​​the side wall is achieved by means of a skirt (flange) which projects vertically downward from the rotating cover and engages in a guide (also called a sandbag) containing a sealing material (e.g. sand). The guide can be arranged on the top side of the outer steel support, approximately in the horizontal direction next to the corresponding rail element.

[0042] In one embodiment, the glass melting tank furnace is designed to supply the raw material mixture and / or glass cullets from above into the glass melting tank furnace through at least one corresponding dust-proof sealed opening in the cover, so that the raw material mixture and / or glass cullets are placed continuously and over a large area on the surface of the glass melt, for example, in the form of one or more annular strips. Thereby, a uniform distribution of the raw materials (raw material mixture and glass cullets) on the surface is achieved, and a favorable operation of the glass melting tank furnace is achieved more effectively according to the cold top principle. "Large area" placement means that the raw material mixture and / or glass cullets are placed on at least 40% of the glass melt surface, and due to the formed bulk cone and the movement of the cover on the glass melt, these raw material mixtures and / or glass cullets are distributed on the entire surface of the glass melt.

[0043] In one embodiment, the feeding device and the rotating cover are designed so that the raw material mixture and / or the crushed material are supplied to the glass melting tank furnace through a plurality of dustproof sealing openings in the rotating cover. In particular, the supply can be carried out through two or more openings, which are arranged side by side with each other in the radial direction of the rotating cover, for example, so that the raw material mixture and / or the crushed material are distributed more evenly on the surface of the glass melt. In another embodiment, at least two opening groups arranged side by side with each other in the radial direction can be provided for supplying the raw material mixture and / or the crushed material, which further makes the distribution uniform and reduces the rotation angle required for the rotation of the rotating cover when necessary. The feeding device can be designed, for example, so that at least one fixed storage container for the raw material mixture and / or the crushed material is provided above the glass melting tank furnace, and the raw material mixture and / or the crushed material is supplied from the storage container to at least one storage container movable with the rotating cover at a properly coordinated time point by means of a metering and dispensing device. For example, when the movable storage container is located below the fixed storage container along the rotational movement of the rotating cover, the raw material mixture and / or the crushed material can be supplied in sufficient quantity. Alternatively, a flexible feed tube may be provided, which connects the outlet of the metering device to the inlet of a storage container that can be moved with the rotating cover during the rotation of the rotating cover. The raw material mixture and / or the crushed material are then further distributed on the openings in the rotating cover from the storage container that can be moved with the rotating cover, for example, by means of another conveying and / or metering device (for example, a vibrating guide trough or a screw conveyor). If at least two groups of openings are provided, the openings of one group are arranged offset in the radial direction relative to the openings of the other group, so that the surface of the glass melt can be uniformly provided with the supplied raw material mixture / glass crushed material. The conveying and / or metering device can, for example, be designed so that at least one opening located radially further inwardly obtains a smaller amount of raw material mixture and / or crushed material than at least one opening located radially further outwardly, because the area on the surface of the glass melt to be covered by the corresponding openings is correspondingly different when the rotating cover rotates.

[0044] As described above, the flow direction of the glass is generally from top to bottom (vertical), that is, from the surface of the glass melt toward the direction of the homogenizing bottom section of the internal space of the tank furnace, wherein at least one outlet opening through which the molten glass is pulled out is arranged in the region of the homogenizing bottom section, the lower end of the transition wall and / or the lower end of the side wall. Here, the outlet opening can be located at the height of the lower end of the transition wall or below it in the vertical direction, that is, approximately at the height of the homogenizing bottom section. The lower edge of the outlet opening can, for example, be located at the height of the homogenizing bottom section or below it in the vertical direction. In one embodiment, one, two or three side-by-side or opposite outlet openings are arranged at the lower end of the transition wall and / or the lower end of the side wall. In one embodiment, for example, a corresponding groove / notch with a width of at least 400 mm can be arranged in the homogenizing bottom section, and the groove / notch extends in the direction of the outlet opening. In this embodiment, the outlet opening is at least partially or completely located below the vertical height of the homogenizing bottom section. In another case (in which the outlet opening is located at the bottom of the side wall), the side wall extends in the region of the outlet opening to the homogenizing bottom section. In this case, the raised bottom section is interrupted in the region extending radially relative to the axis of the melting and refining chamber / homogenizing chamber. In other words, in this embodiment, a radially extending channel is provided, which is located upstream of the outlet opening in the flow direction of the glass melt and which extends substantially in the radial direction from the homogenizing bottom section to the (downwardly drawn) side wall. The channel has at least one width corresponding to the width of the outlet opening, for example at least 400 mm. In one embodiment, the maximum width of the outlet opening is 1 / 2×d (d=diameter of the homogenizing chamber). In another embodiment, the vertical height of the outlet opening in the new state is less than 1 / 2×h. In one embodiment, the maximum width that the channel can assume is the maximum diameter of the homogenizing chamber.

[0045] In one embodiment, when two outlet openings are used, the outlet openings are arranged relative to each other (corresponding to a circumferential distance of 180° relative to the bottom section or the homogenizing section of the protrusion, depending on the position at which the outlet openings are arranged in the radial direction), and when three outlet openings are used, they have a distance of, for example, 120°.

[0046] In one embodiment, each electrode of the first group can be designed as a top electrode, so that in the production operation state, the electrode extends obliquely from above (i.e., from the surface of the glass melt) into the glass melt vertically or at a small angle to the vertical direction (e.g., maximum 30°, preferably between 5° and 20°) relative to the surface of the glass melt and heats the glass melt from above. In one embodiment, the top electrode can additionally be designed to be pivotable in and out of the interior space of the tank furnace. As a result, each electrode can be easily replaced or updated. Here, the electrodes arranged in / on the side walls are accessible from the outside. Each top electrode has a corresponding pivotable holder.

[0047] In one embodiment, each electrode of the second group can be designed as a bottom electrode, so that in the production operation state, the electrode extends obliquely from below (i.e., from the raised bottom section) into the glass melt vertically or at a small angle to the vertical (e.g., maximum 30°, preferably between 5° and 20°) relative to the surface of the glass melt and heats the glass melt from below. In one embodiment, the bottom electrode can additionally be designed to be able to be pushed into the interior space of the tank furnace. As a result, each electrode can be easily updated. Here, the electrode arranged in the raised bottom section can be contacted from below.

[0048] In one embodiment, at least one step and / or at least one recess is arranged on the side wall or in the side wall on the corresponding hot chamber side. The at least one recess in / on the side wall of the glass melting tank furnace can, for example, be arranged for arranging at least one top electrode or pivoting at least one top electrode inwardly and / or outwardly. For example, a step arranged above the side wall can be configured so that the step reduces or increases the annular width of the inner space of the tank furnace compared to below the step.

[0049] According to the invention, the glass melting tank furnace is provided with a plurality of electrodes for heating the glass melt, wherein the required number of electrodes for heating the glass melt in the production operation state and their energy supply are determined based on the melting and fining energy required for the predetermined glass output. The total number of electrodes can be, for example, 18, 24, 36 or 42, wherein the first group and the second group can have different or the same number of electrodes. For this purpose, the average current density obtained on the surface of the corresponding electrode can be considered as a boundary condition parameter, and the average current density should not exceed 3A / cm 2 In addition, the current carrying capacity of the electrode holder system should not exceed approximately 3600A.

[0050] Due to the arrangement of the electrodes of the first group close to the side wall and the electrodes of the second group close to the transition wall, the electrodes are arranged, for example, on at least two circumferentially concentric circles or circular lines (seen in horizontal section) and are interconnected in such a way that the voltage (for safety reasons) does not exceed 500 V and the current intensity of 3600 A. The outer (larger) circle / line is located on the side wall or at a radial distance of 150 mm to 800 mm, typically 330 mm, from the hot chamber side of the side wall, while the inner (smaller) circle / line is arranged in each case on the bottom section of the projection at a distance of at least 500 mm, typically 750 mm, from the transition wall and at a predetermined distance from the circle / circular line of the first group of electrodes. The electrodes can be arranged individually or in pairs uniformly distributed / equidistantly along the circumference on the corresponding circle / line. In order to achieve a current distribution that is as uniform as possible and thus a uniform loss of electrodes, as described above, each three electrodes or each three electrode pairs arranged side by side on the line or circle can be arranged on the outer circle at a distance from each other that is smaller than the distance to the corresponding nearest electrode / electrode pair. The distance between the two outer electrodes / electrode pairs of the three electrodes / electrode pairs is advantageously approximately the same as the distance between the central electrode / electrode pair and the opposing electrode / electrode pair of the second group.

[0051] If the ratio DEG2 / DEG1 of the diameter DEG2 of the circle or circular wire of the second electrode group to the diameter DEG1 of the circle or circular wire of the first electrode group is in the range between 0.45 and 0.7, a good flow distribution can be achieved in the melting and refining chamber. This applies in particular when the electrodes of the first group are designed as top electrodes or bottom electrodes.

[0052] In one embodiment, in order not to exceed the above-mentioned limits of the electrode current density and the electrode current of each electrode, an installation mode in which every two electrodes are closely arranged side by side and electrically connected in parallel can be used. Thus, a higher number of electrodes is achieved. It can be said that the electrodes closely arranged side by side and connected in parallel form a continuous "virtual electrode" to some extent electrically. Alternatively, a single electrode can be used for each electrode pair.

[0053] In order to supply energy to the electrodes, an energy supply device is provided, which realizes a circuit that makes the load of the electrodes uniform and symmetrical. Suitable electrical connections map the arrangement of the pointers in the electrical phasor diagram to the geometrically similar arrangement of the electrodes in the corresponding new glass melting tank furnace. The number and arrangement of the pointers in the electrical phasor diagram are determined by the number and configuration of the transformers provided in the energy supply device. This can be implemented in various electrical connections, for example:

[0054] Scott-T circuit: In which the number of connected electrodes is a multiple of four,

[0055] Interconnected three-phase system: where the number of connected poles is a multiple of three,

[0056] Open three-phase system: in which the number of connected poles is a multiple of 6.

[0057] An open three-phase system offers the advantage of less loading on the melting electrodes and is therefore preferably used.

[0058] In particular, in open three-phase systems, there are other variants of the various connections on the primary side of the transformer, in particular delta connection and star connection are possible. These connections can also be combined with one another.

[0059] Furthermore, it is conceivable to divide the electrodes arranged in the interior of the furnace into two or more sections of the interior of the furnace, so that the electrodes of each section form their own heating circuit.

[0060] In addition, the above object is achieved by a glass melting device having the above glass melting tank furnace, wherein the glass melting device also has a feed system for supplying a raw material mixture and / or glass cullets and an energy supply device for a plurality of electrodes, wherein the energy supply device is connected to each electrode. The glass melting device has the advantages described above with respect to the glass melting tank furnace.

[0061] The above object is also achieved by a method for manufacturing the above glass melting tank furnace, the method comprising the following steps:

[0062] providing a first grid element for a side wall of a glass melting tank and a second grid element for a transition wall, and providing a bottom plate,

[0063] The first grid element and the second grid element are arranged and fixed at or on the raised bottom section of the glass melting tank furnace and the bottom plate is arranged and fixed in the area of ​​the bottom so that the side wall on the hot chamber side above the raised bottom section basically forms a polygon, circle or ellipse with at least five sides in a horizontal cross section, wherein the bottom has a raised bottom section surrounding at least 70% of the circumference of the inner space of the tank furnace and a homogenizing bottom section surrounded by the raised bottom section and deeper than the raised bottom section, wherein the raised bottom section extends laterally from the hot chamber side of the side wall toward the inner space of the tank furnace and has a width greater than or equal to 0.25×D, wherein D is the average diameter of the inner space of the tank furnace above the raised bottom section, wherein a transition wall extending vertically or almost vertically relative to the surface of the glass melt is formed at the transition from the raised bottom section to the homogenizing bottom section, and

[0064] A plurality of electrodes are arranged which heat a glass melt in a production operation state, wherein in the production operation state, the surface of the glass melt is located above the raised bottom section, so that a first group of the plurality of electrodes is in an area above the raised bottom section adjacent to the side wall or extends from the raised bottom section into the glass melt, and a second group of the plurality of electrodes is arranged in an area in the raised bottom section adjacent to the transition wall and extends from the raised bottom section into the glass melt, so that for the glass melt in the inner space of the tank furnace, a melting and refining chamber is formed above the level of the raised bottom section and a homogenizing chamber is formed below this level, wherein the homogenizing chamber is surrounded by the transition wall on the side and by the homogenizing bottom section on the bottom.

[0065] By means of the above method, the above glass melting tank furnace can be realized in a simple and cost-effective manner. It has been described above that the grid elements can be arranged side by side and, if necessary, can also be arranged in a stacked manner. The grid elements are preferably fixed by means of the above external steel brackets. The materials that can be used for the grid elements have also been given above.

[0066] Corresponding simulations have shown that the above-mentioned glass melting tank furnace is suitable for glass production in the range of 80 tons / day to 450 tons / day. The following parameters of the above-mentioned glass melting tank furnace and the parameters of the following embodiments are also determined based on simulations and various experiments. Here, computational fluid dynamics (CFD) is used as a simulation method. This method can be used to calculate flow curves and temperature curves, for example, and thereby determine the quality index of the simulated glass melt known to those skilled in the art. The average diameter D of the glass melting tank furnace relative to the side wall above the raised bottom section of the hot chamber can be, for example, between 5m and 16m. The average diameter d of the homogenizing chamber between the relative areas of the transition wall relative to the hot chamber side can be, for example, between 2.5m and 8m. As already given above, the glass level depth T until the homogenized bottom section can be realized as, for example, 1.3m to 3.2m. Therefore, compared with the glass level depth T, the internal space of the tank furnace has a greater height (in the vertical direction) H. The melt area (the surface of the glass melt under production operation) can be, for example, between 19.5m 2 and 200m 2 between.

[0067] The novel glass melting tank furnace can be used for soda-lime glass, borosilicate glass, fiber glass or other types of glass.

[0068] The invention is explained below based on embodiments and with reference to the accompanying drawings. All features described and / or illustrated herein, either alone or in any combination, constitute the subject matter of the invention, regardless of their generalization or reference in the claims. In the drawings:

[0069] Figure 1A first embodiment of a glass melting tank furnace and a glass melting device is schematically shown in a partially cut-away side perspective view,

[0070] Figure 2 , Figures 2a to 4 Three vertical sections ( Figure 2 , Figure 2a , Figure 2b , Figure 2c ), with reference marks on the horizontal section ( Figure 3 ) and again in horizontal sections without reference marks ( Figure 4 ) schematically shows the Figure 1 Glass melting tank furnace, including Figure 2b and Figure 2c shows the simulation data of the embodiment,

[0071] Figures 5 and 6 In top view ( Figure 5 ) and bottom view ( Figure 6 ) schematically shows the Figure 1 Glass melting tank furnace and feeding system,

[0072] Figures 7 and 8 The vertical section ( Figure 7 ) and horizontal cross section ( Figure 8 ) schematically shows a second embodiment of a glass melting tank furnace,

[0073] Figures 9 and 10 The vertical section ( Fig. 9 ) and horizontal cross section ( Fig.10 ) schematically shows a third embodiment of a glass melting tank furnace,

[0074] Fig.11 A fourth embodiment of a glass melting tank furnace and a feed system are schematically shown in a partially cut-away side perspective view,

[0075] Figure 12 to Figure 13 The vertical section ( Fig.12 ) and horizontal cross section ( Fig.13 ) schematically shows the Fig.11 Glass melting tank furnace,

[0076] Fig.14 The bottom view schematically shows the Fig.11 Glass melting tank furnace,

[0077] Figure 15 to Figure 16 The vertical section ( Fig.15 ) and horizontal cross section ( Fig.16 ) schematically shows a fifth embodiment of a glass melting tank furnace,

[0078] Fig.17A sixth embodiment of a glass melting tank furnace and a feed system are schematically shown in a partially cut-away side perspective view,

[0079] Figure 18 to Figure 19 The vertical section ( Fig.18 ) and horizontal cross section ( Fig.19 ) schematically shows the Fig.17 Glass melting tank furnace,

[0080] Figure 20 to Figure 21 In top view ( Fig. 20 ) and bottom view ( Fig.21 ) schematically shows the Fig.17 Glass melting tank furnace,

[0081] Fig. 22 A seventh embodiment of a glass melting tank furnace and a feed system are schematically shown in a partially cut-away side perspective view,

[0082] Figure 23 to Figure 24 The vertical section ( Fig.23 ) and horizontal cross section ( Fig.24 ) schematically shows the Fig. 22 Glass melting tank furnace,

[0083] Figure 25 to Figure 26 In top view ( Fig.25 ) and bottom view ( Fig.26 ) schematically shows the Fig. 22 Glass melting tank furnace,

[0084] Fig. 27 An eighth embodiment of a glass melting tank furnace and a feed system are schematically shown in a partially cut-away side perspective view,

[0085] Figures 28 to 30 The side perspective view schematically shows the Figure 1 A section of a side wall of an embodiment of the present invention, the section of the side wall having a top electrode and an electrode holder, wherein the electrode is in a production operation state ( Fig.28 ) and the electrodes are in a partially outwardly pivoted state or a fully outwardly pivoted state ( Fig.29 and Fig.30 ),

[0086] Figure 31 to Figure 32 The side perspective view schematically shows the Figure 1 The region of the raised bottom section of the embodiment of the present invention has a bottom electrode and an electrode holder, wherein the electrode is lowered ( Fig.31 ) and the electrode is in production operation ( Fig.32 ),

[0087] Fig.33schematically shows a vertical section through the upper region of the side wall of a ninth embodiment of one of the glass melting tank furnaces and through the rotating cover, and

[0088] Fig.34 Schematically shows the Figure 1 A horizontal cross section of a glass melting tank furnace showing the interconnection of the electrodes of this embodiment.

[0089] The embodiments of the glass melting tank furnace or glass melting device described below include top electrodes as the first set of electrodes, which are arranged in the area adjacent to the side wall. The embodiments can also be realized similarly by bottom electrodes extending from the bottom section of the protrusion into the glass melt or by side electrodes extending from the side wall into the glass melt in the horizontal direction. Similar to the top electrodes, the bottom electrodes have a predetermined distance from the hot chamber side of the side wall.

[0090] Figures 1 to 6 , Figure 28 to Figure 32 and Fig.34 The first embodiment of the glass melting apparatus shown includes a glass melting tank furnace 10. Figure 1 The figure is shown in a partially cutaway manner so that the inner space 11 of the tank kiln can be seen. Figures 1 to 4 As shown, the inner space 11 of the tank furnace in which the glass melt 12 is arranged is laterally delimited by side walls 13. In addition, a raised bottom section 14 and a homogenized bottom section 15 are provided, which together delimit the inner space 11 of the tank furnace from below. The raised bottom section 14 and the homogenized bottom section 15 are connected to each other by a transition wall 16 extending vertically (perpendicular to the surface of the glass melt 12), thereby forming a step in the glass melting tank furnace 10. The glass melting tank furnace 10 works according to the cold top principle and therefore has a cover 12a (see FIG. 1 ) of the glass melt 12 consisting of an unmelted raw material mixture and / or scraps. Figure 2 ), which covers most of the surface of the glass melt 12. As described in more detail below, the raw material mixture and / or scraps are supplied from above the glass melt 12 through a dust-free sealed cover designed as a suspended rotating cover 19 of the inner space 11 of the tank furnace.

[0091] like Figure 2a , Figure 2b and Figure 2c As shown, the inner space 11 of the tank furnace is composed of a cylindrical melting and refining chamber 11a arranged above a raised bottom section 14 and a cylindrical homogenizing chamber 11b connected thereto and arranged concentrically with the melting and refining chamber 11a, wherein the homogenizing chamber 11b is defined on the side by a transition wall 16 and on the bottom by a homogenizing bottom section 15. Figure 2 The common vertically extending axis 11e formed by the melting and refining chamber 11a and the homogenizing chamber 11b is shown in FIG. Figure 2 The cross section shown Figure 2a In the figure, the two sub-chambers 11a and 11b of the inner space 11 of the tank furnace are represented by different shades. Figure 2 and Figure 2a The location of the cross section is Figure 4 In the figure, the dashed line S1 is used to indicate that Figure 2b and Figure 2c The location of the cross section is Figure 4 It is indicated by the dot-dash line S2.

[0092] The side wall 13 has a circular shape and a vertical height H above the raised bottom section 14 (relative to the horizontal cross section), so that the melting and refining chamber 11a is formed substantially cylindrically. In this embodiment, the average diameter D between the opposite hot chamber sides of the side wall 13 above the raised bottom section is 14 m. The raised bottom section 14 has a width B of 4.2 m, so that the diameter d of the homogenizing chamber or the distance between the opposite hot chamber sides of the transition wall 16 is about 5.6 m. The height difference h between the circular homogenizing bottom section 15 and the raised bottom section 14 extending around the homogenizing bottom section 15 is about 1.1 m (see Figure 2 ). As can be seen from the table below, based on simulations it can be shown that with this glass melting tank furnace a production of 350 t / d is achievable, with a volume of molten glass of 285.7 m 3 And the surface area of ​​the glass melt is 153.9m 2 .

[0093] In addition, in the glass melting tank furnace 10, an outlet opening 13a is provided at the lower end of the side wall 13, through which the molten glass is pulled out so as to be subsequently processed into, for example, container glass. For this purpose, the side wall 13 extends to the homogenizing bottom section in the region of the outlet opening 13a and is connected to the homogenizing chamber 11b via a channel 11c extending in the radial direction. In the region of the channel 11c, the raised bottom section 14 is interrupted. The lower end of the outlet opening 13a is located at the height of the homogenizing bottom section 15, so that the channel 11c extends straight from the homogenizing bottom section toward the direction of the outlet opening 13a. In the flow direction of the glass melt, the outlet opening 13a is connected to the circulation channel 21, the riser 22 and the working tank furnace 23.

[0094] The glass melting tank furnace 10 has two groups of electrodes. The first group of electrodes 17 (here 24 electrodes) are arranged at a distance of about 250mm to 550mm next to the side wall 13 and are designed as top electrodes. These top electrodes extend into the glass melt 12 from above. These electrodes are also referred to as external electrodes 17 hereinafter. In addition, a second group of electrodes 18 are provided, which are arranged on the raised bottom section 14, with a distance of about 600mm to 800mm from the transition wall, and are designed as bottom electrodes. These bottom electrodes extend into the glass melt 12 vertically upward or slightly inclined relative to the vertical line from the raised bottom section 14. The electrodes of the second group are also referred to as internal electrodes 18. These two groups have a distance, for example, between 2.85m and 3.35m. The distance of the relative internal electrodes 18 is, for example, 6.8m.

[0095] In one embodiment, as in Fig.28 As shown in more detail in FIG. 1 , each external electrode 17 extends into the inner space 11 of the tank furnace through an opening 13d arranged above the side wall 13 and extends into the glass melt 12 from above. Figure 29 to Figure 30 As shown, each external electrode 17 is designed to be Fig.28 The first position shown and Fig.30 In the first position, the electrode 17 is in a working state, wherein the electrode supplies heat energy to the glass melt 12 due to the Joule effect in production operation. In the second position of the electrode 17, the electrode is completely moved out of the tank furnace interior 11 and can be maintained, for example. Fig.29 The position shown represents the removal of the electrode 17 from the inner space 11 of the tank furnace. In order to move the electrode in and out and to arrange it safely in the inner space of the tank furnace, each external electrode has a clamp 17a, with which the electrode can be pivoted and which can fasten the electrode to an external steel support 36 arranged outside the side wall 13. In the production operation state, each electrode is arranged slightly inclined relative to the vertical direction (for example, at an angle of 5° to 20°) (see Fig.28 ), which facilitates the inward and outward pivoting of the electrodes. In one embodiment, each opening 13d is dust-tight in production operation. Specifically, this embodiment has twelve internal electrodes 18 and twenty-four external electrodes 17, which are arranged in pairs and are also arranged evenly distributed along the side wall 13 or the transition wall 16 / next to the side wall 13 or the transition wall 16. Alternatively, the external electrodes can also be arranged in groups of three pairs, the distances between these pairs and the adjacent pairs being smaller than when these pairs are evenly distributed over the entire circumference. No electrodes are arranged in the area of ​​the channel 11c.

[0096] The inner electrode 18 is designed as a bottom electrode, which in the production operation state extends vertically upward from the raised bottom section 14 into the glass melt 12, such as Fig.32 As shown in more detail in Fig.31 and Fig.32 As shown, each electrode 18 is designed to be displaceable so that they can be replaced or adjusted in the event of wear. The electrode is introduced into the inner space 11 of the tank furnace through the hole 14a of the bottom section 14, and the inner space of the tank furnace is closed by an electrode brick 12b made of a particularly high-strength refractory material (for example, AZS with a high zirconium content of at least 41%). In addition, the electrode 18 has a hollow cylindrical insulation and cooling unit 18a, which is cooled, for example, with water. In addition, a clamping device 18b is provided, by which the electrode 18 is fastened to the cold chamber side of the raised bottom section 14. In addition, the clamping device 18b is designed so that it can manually displace the electrode 18 in the vertical direction along a guide rail extending parallel to the electrode. Thereby, a defined adjustment of the electrode 18 can be achieved. Fig.31 The electrode 18 is shown in a state in which the electrode 18 is retracted.

[0097] As already explained above, the arrangement of the electrodes and the dimensions of the raised bottom section 14, the transition wall 16 and the homogenizing bottom section 15 result in the formation of convection zones KB1 to KB6 between the opposing electrodes in the melting and refining space 11a, thereby achieving good melting of the raw material and achieving good refining. Here, the convection zones located between the two electrodes and rotating in opposite directions are convection zones KB1 and KB2, KB3 and KB4, and KB5 and KB6. Two further convection zones KB7 and KB8 are formed between the electrode 17 and the side wall 13. Convection zones KB1 to KB8 are located between the electrodes 17 and the side wall 13. Figure 2b The simulation shown is shown, and because the arrows in the simulation are very small, Figure 2c Here, the glass melting tank furnace 10' used for the simulation does not completely correspond to Figure 1 , Figure 2 , Figure 2a , Figure 3 and Figure 4 The glass melting tank furnace 10 shown in FIG. Figure 2b and Figure 2c In a variation of this, the outlet opening 13a' is arranged slightly deeper, and the external electrode 17' is arranged at Figure 1 , Figure 2 , Figure 2a , Figure 3 and Figure 4 In addition, it should be noted with respect to the convection bands KB3, KB4 and KB5 that these convection bands extend partially into the plane of the drawing, so that Figure 2bThis is not clearly visible in the simulated data shown.

[0098] exist Figure 2b In the simulation, the direction of each arrow indicates the flow direction of the glass melt relative to the corresponding position in the glass melt, and the length of each arrow indicates the magnitude of the velocity. In the melting and fining area 11a, the convection is in the form of convection bands KB1 to KB8, which are very large. Figure 2b It also emerges from the simulation shown that, by comparison, the flow that can be observed in the homogenization chamber 11b (or in its main section below the transition section) is lower. The vertical component of the velocity of the glass melt flowing toward the outlet opening 13a is smaller than or of the same order of magnitude as the buoyancy-related velocity of the gas bubbles contained in the glass melt. This can also be seen from the following table, which contains measured values ​​determined with the aid of the simulation. The measured values ​​are Figure 2c The measurement is performed at a total of 11 different measuring points M1 to M11 in the cross section S2 shown, wherein the measuring points M1 to M11 are Figure 2c Shown in.

[0099]

[0100]

[0101] The simulation with the aid of CFD is based on the following dimensions of the glass melting tank 10': D = 14 m; d = 5.6 m; h = 1.1 m; H = 1.8 m. The first set of electrodes 17 is arranged at a distance of 0.75 m from the hot chamber side of the side wall 13, and the second set of electrodes 18 is arranged at a distance of 0.6 m from the transition wall 16. The glass density (under production conditions) is 2.4 t / m 3 Soda-lime glass was used as the glass type for simulation use.

[0102] Especially in Figure 1 , Figure 5 and Figure 6 The disc-shaped rotating cover 19 shown in the figure seals the inner space 11 of the tank furnace at the top with respect to heat losses, dust and exhaust gases, wherein the dust and exhaust gases are sucked into the filter system. The rotating cover has nine dust-tightly sealed openings 19a, of which four or five are arranged side by side with each other in the radial direction. Negative pressure is generated by means of a suction device. The raw material mixture and / or crushed material are supplied to the inner space 11 of the tank furnace, in particular to the surface of the glass melt 12, through the openings 19a. The rotating cover 19 is designed as a suspended rotating cover, and its top side is rotatably fastened to a steel bracket extending above the top side of the glass melting tank furnace 10, which is Figure 1 , Figure 5 and Figure 6 Not shown in FIG.

[0103] The feed device has a fixed storage container (not shown) with a metering and dispensing device. In addition, a storage container 24 is provided on each side, which rotates with the rotating cover 19. The raw material mixture and / or the crushed material enter the screw conveyor or the vibration guide 27 from each storage container 24 rotating with the rotating cover 19, and are respectively transported through the through opening 19a by means of the smaller vibration guide via the further rotating storage container 28 into the tank furnace interior 11 and onto the surface of the glass melt 12. Since the rotating cover 19 performs a rotational movement around the rotation axis extending approximately in the region of the vertical axis 11e of the melting and refining chamber 11a or the homogenizing chamber 11b, most of the surface of the glass melt 12 located in the tank furnace interior 11 is successively covered by the (cold) cover 12a composed of the raw material mixture and / or crushed material. An approximately annular blanket composed of the raw material mixture and / or crushed material is formed through each opening 19a. In the embodiment shown, each opening 19a in a first group connected via a screw conveyor or a vibrating guide 27 is arranged offset in the radial direction relative to the opening 19a in a second group connected via another screw conveyor or a vibrating guide 27, so as to achieve a uniform distribution of the raw material mixture or crushed material on the surface of the glass melt 12. When each storage container 24 is guided past a fixed storage container (not shown) during the 360° continuous rotation movement of the rotating cover and placed under the fixed container for a predetermined time, each storage container 24 receives further raw material / crushed material from the fixed container. In addition, the metering distribution, in particular to the screw conveyor or the vibrating guide 27, can be designed so that the other storage containers 28 rotating together located further inside receive less raw material than the storage containers 28 rotating together located further outside.

[0104] The side walls 13 and the transition wall 16 are formed by stacked and side-by-side arranged grid elements. Figure 1 In the sectional view of FIG. 1 , a small shoulder 13e is arranged above the side wall 13 in the region where the opening 13d for the external electrode 17 is arranged, which is formed by horizontally extending grid elements. During the production of the glass melting tank furnace 10, these grid elements are arranged side by side or stacked, fastened to or beside the raised bottom section 14 or to or beside the homogenizing bottom section 15, as shown in the figure, and are held by steel brackets 36 and steel brackets 38, as described above.

[0105] The following will be based on Fig.34 The interconnection of the outer electrodes 17 and the inner electrodes 18 is explained. As explained above, in the furnace inner space 11, twelve pairs of top electrodes 17 are arranged in the region adjacent to the side walls 13 and six pairs of bottom electrodes 18 are arranged in the region adjacent to the transition wall 16.

[0106] In this embodiment, there is provided Figure 1 , which has three transformers for supplying a total of 36 electrodes 17, 18. The 36 electrodes are divided into three groups of 6 electrode pairs each, each group being assigned a transformer, wherein an open three-phase system is used. The two transformers are connected in a delta connection on the primary side (offset by 60°, the first delta connection at Fig.14 The first connection is indicated by a dotted line in the figure and the second delta connection is indicated by a dashed line), wherein the delta connection in each case comprises an opposing inner electrode (pair) 18 and an outer electrode (pair) 17. In addition, one transformer is implemented as a star circuit (see the interconnection indicated by a dotted line), wherein the star circuit comprises only the outer electrode (pair). Since the geometrical / mechanical arrangement of the electrodes in the glass melting tank furnace follows the position of the pointer in the electrical phasor diagram, a uniform current load is obtained for all electrodes. In addition, since the paths between the associated electrodes / "heating pairs" are not too long, manageable values ​​for the operating voltage / secondary voltage are obtained.

[0107] In the above embodiment (and all other embodiments described below), in order not to exceed the above limits of the electrode current density and the electrode current of each bottom electrode or top electrode, an installation mode in which every two top electrodes or bottom electrodes are arranged closely side by side and electrically connected in parallel is adopted. Thus, a higher number of electrodes is achieved. It can be said that the top electrodes arranged closely side by side and connected in parallel electrically form a "virtual electrode" with a uniform and continuous load to a certain extent. Alternatively, a single electrode can be used for each electrode pair.

[0108] Further embodiments and design variants are described below. Here, the differences from the first embodiment and other embodiments are particularly mentioned. Since the glass melting tank furnace has basically the same structure, not all elements in each embodiment are described. The same elements have the same reference marks in the tens and ones of the corresponding digits of the reference marks, where the reference marks of different embodiments differ by a whole hundred. For example, the external electrode has the reference mark 18 in the first embodiment, the reference mark 118 in the second embodiment, and the reference mark 218 in the third embodiment, and so on. Please refer to the first embodiment mentioned above for the description of the individual elements.

[0109] Figure 7 and Figure 8The second embodiment of the glass melting tank furnace 110 shown has an average diameter D of 11m above the raised bottom section 114. Correspondingly, the average diameter d in the region of the homogenizing chamber is about 5.4m. The channel 111c connecting the homogenizing chamber with the outlet opening 113a in the region of the side wall 113 has a channel-shaped recess 111d, which makes the lower end of the outlet opening 113a located below the homogenizing bottom section 115. The recess 111d extends into the homogenizing bottom section 115. This is conducive to pulling out a well-homogenized glass melt. The width of the recess 111d in the horizontal direction is, for example, 400mm.

[0110] The third embodiment of the glass melting tank furnace 210 corresponds to the second embodiment, wherein the width of the raised bottom section 214 in the horizontal direction is implemented to be larger than in the case of the second embodiment. The diameter d in the region of the homogenization chamber is about 3.6 m, so the width is increased from 2.8 m (the width of the raised bottom section 114 of the second embodiment) to 3.7 m. As a result, the internal electrodes 18 are closer together, and the flow in the melting and refining chamber becomes uniform, which has a positive effect on the glass quality.

[0111] Figures 11 to 14 The fourth embodiment of the glass melting tank furnace 310 shown differs from the first embodiment in that, due to the corresponding design of the transition wall 316 and the raised bottom section 314, the homogenization chamber has the shape of a six-sided prism. The width B of the melting and refining chamber above the raised bottom section 314 is, for example, 14 m, and the average diameter d of the homogenization chamber is, for example, 7 m. In addition, the height difference h=1.8 m is greater than in the first embodiment. This also achieves better homogenization of the glass melt 12. In this embodiment, the outlet opening 313a is arranged at the lower end of the transition wall 316. As Fig.13 As shown, the raised bottom section 314 extends completely around the homogenization chamber (i.e., without being interrupted by the passage). In addition, a rotating storage container for the raw material mixture and / or the crushed material is arranged in the center of the glass melting tank furnace 310 above the screw conveyor or the vibration guide 327. Correspondingly, the fixed storage container is also centrally located above the glass melting tank furnace 310.

[0112] Fig.15 and Fig.17 The fifth embodiment of the glass melting tank furnace 410 shown differs from the fourth embodiment in that the diameter d of the homogenization chamber is smaller (here 4.7 m), and therefore the width of the raised bottom section 414 is larger (b=4.7 m). The dynamic processes in the melting and refining chambers can be balanced by the more uniform electrode arrangement caused by the widening of the raised bottom section 414.

[0113] exist Figures 17 to 21, a sixth embodiment of a glass melting tank kiln 510 is shown. The sixth embodiment differs from the third embodiment in the shape of a channel 511c, which extends from the homogenization chamber to the outlet opening 513a and is used to discharge the homogenized glass melt. In this embodiment, the width of the channel 511c in the horizontal direction corresponds to the average diameter d (d=3.6m) of the homogenization chamber. This reduces the wear of the refractory material in the region of the channel 511c and can be simply implemented. However, the area of ​​the raised bottom section 514 opened by the channel 511c is thereby reduced. Therefore, the internal electrode 518 arranged next to the channel 511c must be slightly shifted, because the electrode 518 should be arranged at a certain distance from the channel 511c in the horizontal direction. The glass melting tank kiln 510 also has a feeding device for supplying a raw material mixture and / or glass scraps similar to the fourth embodiment.

[0114] Figure 22 to Figure 26 The seventh embodiment of the glass melting tank furnace shown is very similar to the first embodiment. The difference from the first embodiment is that the seventh embodiment has two outlet openings 613a, which are arranged oppositely at the bottom of the side wall 613 along the circumferential direction. Thereby, uniform discharge of homogenized molten glass is achieved. Accordingly, two channels 611c are arranged oppositely, and the two channels guide the molten glass to the corresponding outlet openings 613a.

[0115] For glass with higher quality requirements, such as Fig. 27 In the eighth embodiment of the glass melting tank furnace shown, a flange 716a may be provided at the transition wall 716, the flange having a height of about 100 mm measured from the raised bottom section 714 in the vertical direction and a width of 150 mm in the horizontal direction, for example. The flange is integrated into the region of the inner edge in the raised bottom section and only a raised structure is formed on the bottom section. The flange 716a prevents bubbles from flowing directly to the outlet opening 713a.

[0116] Finally, based on Fig.33 The ninth embodiment of the glass melting tank furnace 810 is shown to explain the structure of the glass melting tank furnace with respect to the steel support in more detail. Fig.33 In the illustrated embodiment, three through openings 819a are arranged in the rotary cover 819, and these through openings are used to supply the raw material mixture and / or the scraps. Apart from this, the glass melting tank furnace 810 has the structure of the first embodiment.

[0117] The side wall 813 has an outer steel bracket 36, which holds and fastens the bar elements of the side wall 813. A circular guide 36a is provided on the upper end face of the outer steel bracket 36, on which the roller 819c is guided, so that the rotating cover can rotate 360° in a first rotation direction and in the opposite rotation direction. The roller 819c is connected to the steel bracket 38 of the rotating cover 819. In addition, the steel bracket 38 of the rotating cover 819 has an annular sealing skirt 819d with a sealing edge, wherein each sealing skirt 819d is respectively guided in a circular sealing guide groove 36b with sand for sealing. The sealing guide groove 36b is arranged on the upper end side of the side wall 813.

[0118] The above-mentioned design examples and other variants of the glass melting tank furnace are summarized below based on the following table. There are 12 examples in total. The design of the glass melting tank furnace is derived on the basis of simulations, wherein the dimensions are always measured with respect to the corresponding hot chamber side.

[0119]

[0120]

[0121]

[0122] Here, D is the diameter above the raised bottom section, the area A1 is the size of the melt surface, and H is the height of the side wall above the raised bottom section (see Figure 2 and Figure 3 ), DEG1 is the diameter of the horizontal circle / line in which the first set of electrodes (in the case where these electrodes are top electrodes or bottom electrodes) are arranged, d is the diameter of the homogenization chamber, A2 is the cross-sectional area of ​​the homogenization chamber, h is the height of the homogenization chamber or the height difference between the raised bottom section and the homogenizing bottom section, DEG2 is the diameter of the horizontal circle / line in which the second set of electrodes are arranged, DEG2 / DEG1 is the ratio of the diameters DEG2 and DEG1, is the ratio of the width of the raised bottom section to the radius of the melting and refining chamber, V is the volume of the glass melt arranged in the corresponding glass melting tank furnace, B is the width of the raised bottom section, the output is related to the surface of the glass melt and to the day, T is the daily output, and spVP is the specific volume load (spezifische Volumenbelastung) as the output related to the melt volume and to the day.

[0123] With regard to the above-mentioned new design of the glass melting tank furnace with a circumferentially raised bottom section and a homogenizing bottom section and the described electrode arrangement, it has been shown by means of simulation that an average output (80 tons / day to 450 tons / day, in particular 220 tons / day to 350 tons / day) can be achieved, which means that the output is significantly increased compared to conventional all-electric glass melting tank furnaces. The model predicts a good glass quality of significantly less than 10 bubbles per 100 grams. The compactness of the device is also conducive to its use. With regard to high glass quality, it seems particularly advantageous to realize a wide raised bottom section and a deep homogenizing chamber. Therefore, the present invention enables a range of output that was previously unachievable for all-electric heating. Compared to conventional glass melting tank furnaces, the realization of such a glass melting tank furnace is not too complicated.

Claims

1. A glass melting tank furnace for fully electrically heating a glass melt arranged in an inner space of the tank furnace under production operation conditions, the glass melting tank furnace having a stepped bottom and side walls, wherein the inner space of the tank furnace is defined downward by the bottom, and the side walls surround the inner space of the tank furnace on the sides, wherein in the production operation condition, the glass melt is arranged in the inner space of the tank furnace, wherein the side walls substantially form a polygon, a circle or an ellipse with at least five sides in a horizontal cross section on the hot chamber side above the raised bottom section, wherein the bottom has the raised bottom section surrounding at least 70% of the circumference of the inner space of the tank furnace and a homogenized bottom section surrounded by the raised bottom section and having a deeper center relative to the raised bottom section, wherein the raised bottom section extends laterally from the hot chamber side of the side walls toward the inner space of the tank furnace and has a width (B) greater than or equal to 0.25×D, wherein D is the average diameter of the inner space of the tank furnace above the raised bottom section, wherein A transition wall extending vertically or almost vertically relative to the surface of the glass melt is formed at the transition from the raised bottom section to the homogenizing bottom section, wherein the glass melting tank furnace has a plurality of electrodes, and the plurality of electrodes heat the glass melt arranged in a melting and refining chamber in the production operation state, wherein in the production operation state, the surface of the glass melt is located above the raised bottom section, and a first group of the plurality of electrodes is in the area adjacent to the side wall above the raised bottom section or extends from the raised bottom section into the glass melt, and a second group of the plurality of electrodes is arranged in the area adjacent to the transition wall in the raised bottom section and extends from the raised bottom section into the glass melt, so that for the glass melt in the internal space of the tank furnace, a melting and refining chamber is formed above the level of the raised bottom section and a homogenizing chamber is formed below the level, wherein the homogenizing chamber is surrounded by the transition wall on the sides and by the homogenizing bottom section on the bottom.

2. The glass melting tank furnace according to claim 1, characterized in that: The inner space of the tank kiln is covered from above by a cover, which closes the inner space of the tank kiln in an almost completely dust-tight manner.

3. A glass melting tank furnace according to any one of the preceding claims, characterized in that The cover is designed as a rotating cover, the rotating cover substantially has the shape of a disk, and the rotating cover is preferably designed as a suspended rotating cover.

4. A glass melting tank furnace according to any one of the preceding claims, characterized in that The glass melting tank furnace is designed such that it can be operated according to the cold top principle.

5. A glass melting tank furnace according to any one of the preceding claims, characterized in that The raw material mixture and / or crushed material are supplied into the glass melting tank furnace from above through at least one corresponding dust-sealed opening in the cover, so that the raw material mixture and / or crushed material are placed continuously and over a large area onto the surface of the glass melt, for example in the form of one or more annular strips.

6. A glass melting tank furnace according to any one of the preceding claims, characterized in that The height difference h between the raised bottom section and the homogenizing bottom section, i.e. the vertical height of the homogenizing chamber, is at least 0.5 m and / or the average diameter D of the melting and refining chamber is at least 5 m.

7. A glass melting tank furnace according to any one of the preceding claims, characterized in that A collar which is at least 50 mm high and / or at least 50 mm wide is arranged at the transition wall in the region of the raised base section.

8. A glass melting tank furnace according to any one of the preceding claims, characterized in that The glass melting tank has at least one outlet opening which is arranged in the region of the homogenizing bottom section, in the region of the lower end of the transition wall and / or in the region of the lower end of the side wall.

9. The glass melting tank furnace according to any one of claims 3 to 8, characterized in that: The feed device and the rotary cover are designed so that the raw material mixture and / or the crushed material are supplied into the glass melting tank furnace through a plurality of dust-tight openings in the rotary cover.

10. A glass melting tank furnace according to any one of the preceding claims, characterized in that Each electrode of the first group is designed so that each electrode extends into the glass melt obliquely from above at a vertical direction or at a small angle to the vertical direction relative to the surface of the glass melt in the production operation state, and / or each electrode of the second group is designed so that each electrode extends into the glass melt obliquely from the bottom section of the protrusion at a vertical direction or at a small angle to the vertical direction relative to the surface of the glass melt in the production operation state.

11. A glass melting tank furnace according to any one of the preceding claims, characterized in that Each electrode of the first group is designed to be pivotable in and out of the inner space of the tank kiln, and / or each electrode of the second group is designed to be pushed into the inner space of the tank kiln.

12. A glass melting tank furnace according to any one of the preceding claims, characterized in that The energy supply and diameter of the plurality of electrodes are determined based on the melting and refining energy required for a predetermined glass production volume.

13. A glass melting device, which has a glass melting tank furnace according to any one of claims 1 to 12, wherein the glass melting device also has a feeding system for supplying a raw material mixture and / or glass scraps and an energy supply device for the multiple electrodes, wherein the energy supply device is connected to each electrode.

14. A method for manufacturing a glass melting tank furnace according to any one of claims 1 to 12, the method comprising the following steps: providing the side walls of the glass melting tank with first grid elements and the transition wall with second grid elements, and providing a bottom plate, The first grid element and the second grid element are arranged and fixed at or on the raised bottom section of the glass melting tank furnace and the bottom plate is arranged and fixed in the area of ​​the bottom so that the side wall on the hot chamber side above the raised bottom section basically forms a polygon, circle or ellipse with at least five sides in a horizontal cross section, wherein the bottom has the raised bottom section surrounding at least 70% of the circumference of the inner space of the tank furnace and a homogenizing bottom section surrounded by the raised bottom section and deeper in the center relative to the raised bottom section, wherein the raised bottom section extends laterally from the hot chamber side of the side wall toward the inner space of the tank furnace and has a width (B) greater than or equal to 0.25×D, wherein D is the average diameter of the inner space of the tank furnace above the raised bottom section, wherein a transition wall extending vertically or almost vertically relative to the surface of the glass melt is formed at the transition from the raised bottom section to the homogenizing bottom section, and A plurality of electrodes are arranged, which heat the glass melt in the production operation state, wherein in the production operation state, the surface of the glass melt is located above the raised bottom section, so that a first group of the plurality of electrodes is in an area above the raised bottom section adjacent to the side wall or extends from the raised bottom section into the glass melt, and a second group of the plurality of electrodes is arranged in an area adjacent to the transition wall in the raised bottom section and extends from the raised bottom section into the glass melt, so that for the glass melt in the internal space of the pool furnace, a melting and refining chamber is formed above the level of the raised bottom section and a homogenizing chamber is formed below the level, wherein the homogenizing chamber is surrounded by the transition wall on the side and by the homogenizing bottom section on the bottom.

15. The method according to claim 14, characterized in that The cover is arranged above the interior of the kiln tank so that the interior of the kiln tank is covered from above by the cover, thereby closing the interior of the kiln tank in an almost completely dust-tight manner.

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