Title of Invention

PROCESS FOR OPERATING A GLASS MELTING FURNACE AND A GLASS MELTING FURNACE THEREFOR

Abstract

The invention relates to a process for operating a glass melting furnace, in which a protective radiation barrier (8) is positioned between a melting zone (3) and a refining zone (4) with a refining bench (19); the barrier leaves open - above the melt surface (9) of the glass melt - at least one flow channel (8b,21) for the back flow of at least part of the combustion gases 0from the refining zone (4) into the melting zone (3) in which at least one upward current is produced in the glass melt (10) between the middle of the melting zone (3) and the front face (19a) of the refining bench (19); this current is split - inside the glass melt (10) and before reaching the melt surface (9) -into a first part-current moving upstream into the melting zone (3) and a second part-current moving downstream towards the refining bench (19), whereby the second - downstream - current prevents a back flow of glass melt (10) from the refining zone (4) into the melting zone (3).

Full Text

The invention relates to a process for operating a glass melting furnace, in which a protective radiation barrier is positioned between a melting zone and a refining zone, leaving at least one flow channel clear above the melt surface of the glass melt to permit a backflow of at least part of the combustion gases from the refining zone into the melting zone. A glass melting furnace of this type is known from DE 39 03 016 C2. Its primary purpose is to ensure - by means of intimate heat exchange between the combustion gases on the one hand and the charging material and glass melt on the other - that the glass remains liquid if the production process is interrupted, and that the glass is returned quickly and with maximum efficiency to the required operating temperature when operation is resumed. In order to achieve this there is an initial protective radiation barrier in the melting zone; the bottom edge of this barrier is positioned just above the charging material, and the barrier is a contributory factor in the melting of the charging material by means of the counterflow of the hot combustion gases. However, a flow channel for the combustion gases in a second protective barrier, positioned directly in front of the refining zone, causes no significant exchange of heat, because the lower edge of this flow channel is at a perceptible distance from the glass melt. The known solution has a floor outlet for the glass melt, which is positioned in the centre of the tank and in front of the refining bench, and which is difficult to cool. Floor outlets of this type are considerably narrower than the tank floor, i.e. than the distance between the side walls of the tank, and thus have a small flow cross-section. This causes the flow speed in the floor outlets to be very fast, which leads -to high levels of erosion of the hot walls - made from mineral-based materials - which * surround the outlets. US-A-4 882 736 describes a glass melting furnace in which there are floor electrodes beneath the charging zone and at a considerable distance from the refining zone. These electrodes create an upward current in the glass melt, which feeds additional 1 melting heat from below to the charging material. As the flow indicator arrows show, the rising current at this point not only has no effect on the operations in the refining zone but also slows down the backflow of the glass melt, and has no synergistic reciprocal action with the counterflow of the combustion gases, i.e. the gases are drawn off before they reach the upward current of the glass. This means that the charging material is not heated simultaneously and/or at the same point from above by the combustion gases and from below by the floor electrodes. Nor is there a protective radiation barrier above the floor electrodes, the bottom edge of which could form a flow channel for a counterflow of the combustion gases. From these floor electrodes, the floor of the tank rises gradually, like a long ramp, up to the level of the refining bench, on the top of which there is a step. The step is "mounted" over the angle between the sloping tank floor and the refining bench. The function of the step is therefore to control the rate of flow, and not to reinforce the effect of the floor electrodes, which are situated far away in the charging zone. The surface of the refining bench behind the step must therefore be further away from the melt surface, which counters the effect of the refining bench. Under this prior art, it is the floor of the melting zone which creates a flow pattern by which the hot glass at the surface flows back to the floating charge layer. However, this creates a surface current which constantly moves the hot glass heated by burners out of the refining zone and into the charging zone. This forces opposing currents, which are difficult to control, above the sill because charging material is being constantly fed in, and molten glass has to be removed from the furnace. This has a further, and very important, disadvantage: glass which has already been refined, i.e. purified glass melt, is taken back into the charging and melting zone, where it comes into contact with the charging material and therefore has to be refined again. It is therefore the object of the invention to provide an operating process and a glass melting furnace for this purpose, in which the advantages of the furnace described earlier are retained, but which incorporates precautions to reduce the erosion of the bricks of the tank, to ensure that effectiveness is not reduced by heat utilization but is improved even more where appropriate, to prevent any backflow of refined, very hot glass melt from the refining zone into the melting zone, and to ensure that the charging material is melted as early as possible as it passes through the furnace. 2 The solution to this problem is achieved in the process described earlier, according to the invention, by the fact that at least one upward current is created in the glass melt between the centre of the melting zone and the front face of the refining bench; this current splits - within the glass melt and before reaching the melt surface - into a first part-current moving upstream into the melting zone, and a second part-current moving downstream towards the refining bench, this second, downstream, current preventing any backflow of glass melt from the refining zone into the melting zone. The invention also relates to a glass melting furnace having a melting tank with a tank floor and burners for at least partial heating by means of fossil fuel, in which furnace are arranged - between a charging end and an offtake end, and in the direction of movement of the glass - a melting zone having at least one flue for combustion gases, a refining zone with burners and with a refining bench which rises up from the tank floor and which has a front face, and a homogenization zone; between the melting zone and the refining zone, and in front of the latter, there is a protective radiation barrier which leaves open at least one flow channel for a backflow of the combustion gases from the refining zone into the melting zone (3). Under the invention the solution to the problem is achieved, in the case of the glass melting furnace described earlier, in that means are provided - between the centre of the melting zone and the front of the refining bench, in the direction of movement of the glass - by which an upward flow of the glass melt towards the melt surface is created and, on the melt surface, a flow of the glass is created upstream towards the charging end on the one hand, and downstream towards the refining bench on the other. This upward current moves upwards from below, i.e. perpendicular to the overall flow of the glass melt, which moves in a genera! horizontal direction from the charging end to the offtake end, apart from individual, locally-superimposed currents. The overall flow is, therefore, proportional to the throughput of the furnace, taking into account the furnace geometry. The upward current, or a series of upward currents, provides a defined (first) proportion of the surface backflow towards the charging end, and a further defined (second) proportion of the surface forward flow towards the refining 3 zone, but also forms an extremely effective barrier against any backflow of refined, very hot glass melt from the refining zone into the melting zone. Its action in combination with the protective barrier is of crucial importance here; the barrier concentrates the radiant heat from the burner flames in the refining zone within this zone, and ensures that the required high refining temperature is achieved, the exact level of which (like all other temperatures) depends on the type of glass. Nevertheless, the effect of the defined first proportion of the surface backflow towards the charging end still remains, in that the charging material is heated from below and is thus melted more quickly, while at the same time being prevented from moving too far forwards. Depending on the various developments of the invention subject, the means for achieving this effect can consist - either individually or in combination - in the following: a) a features combination consisting of bubblers in the tank floor and a following step, b) a features combination consisting of bubblers and heating electrodes in the tank floor, with no following step, c) a features combination consisting of bubblers in the tank floor and in heating electrodes above the step, d) a step which extends, at a lower level than the surface of the refining bench, from the front face of the latter towards the charging end, e) a features combination consisting of a step and of heating electrodes arranged above it, f) a features combination consisting of a step (17) and of bubblers (18) positioned in it. g) the fact that, where a step is used - positioned in front of the front face of the refining bench and rising up from the floor of the tank - this step g1) extends across the full width of the tank floor (15), g2) has a height which is between 25% and 75% of the height of the refining bench from the tank floor, and 4 g3) extends both against the horizontal direction of flow of the glass melt and underneath the protective barrier. The effect can be increased in that: h) the bottom edge of the protective barrier is submerged in the glass melt, where it leaves free at least one gap-like flow opening for the glass melt above the step which rises up from the tank floor, i) the protective barrier rests on the step by means of at least one support, each support being arranged between two flow openings in such a way that the total width of all the flow openings is, as far as possible, the same as the width of the tank floor, and that the openings are evenly distributed across this width, j) there is - between the rear face of the radiation barrier and the front face of the refining bench - a vertical gap to allow the glass melt to pass through, in which gap at least two heating electrodes are positioned, k) the step extends at least partly under the second protective barrier against the horizontal direction of flow of the glass melt. It is particularly advantageous if there is a further protective radiation barrier inside the melting zone between the flue and the barrier which is in front of the refining zone, this second barrier dividing the melting zone into a first section containing the flue, and a second section, and having a bottom edge which leaves free an additional flow channel, connected in series above the charging material and the glass melt, for a counterflow of the combustion gases from the second section into the first section and towards the flue. This substantially improves heat utilization. The expression "row(s)" of heating electrodes and bubblers does not necessarily mean that these have uniform horizontal or longitudinal spacing between them. It is also possible - and particularly beneficial - to vary the spacing locally in order to affect the "surface density" of the burners and bubblers in such a way that local thermal balances and flow patterns can be set in the best possible manner. The expression "below the protective radiation barrier" does not necessarily mean a position which is within the vertical projection of the barrier towards the tank floor or 5 the step. On the contrary, this definition can also include the possibility that the "means by which an upward flow can be created within the glass" can extend also upstream and downstream of the said second protective barrier, depending on how this is required by the optimum spacing of the components of this "means". The solution according to the invention is also linked to the following advantages: 1. Avoidance of narrow floor outlets - normally of narrow cross-section and highly susceptible to erosion - and of components for the purpose of intensive cooling, 2. Good preventive effects against: a) infiltration of charging material into the refining zone and b) backflow of melt from the refining zone into the melting zone, 3. Good heat exchange between the flows of gas and glass (counterflow), at the points where these are closest together, and 4. Good pre-heating of the melt before it passes over the refining bench. It is known from FR 2 737 487 Al to arrange a row each of heating electrodes and bubblers in front of a rampart-shaped or trapezoid sill which rises up from the floor of the tank, and a further row of heating electrodes behind the sill, in order to create "flow rollers" in the glass melt which have a barrier effect. However, since the roof of the furnace is flat and has no protective radiation barriers, the joint action of the electrodes and bubblers with a barrier, in accordance with the invention, is necessarily absent. Nor is the sill a refining bench; its upper surface is far too short in the direction of flow for this purpose, and this upper surface is far too far away from the melt surface, as the height of the sill may only be half of the depth of the melt at most The very deep refining zone expressly does not begin until after the sill. The advantages detailed above are therefore not achieved, at least not in total... Embodiments of the invention subject arc described below and shown in Figs. 1 to 7. 6 Fig. 1 shows a longitudinal section through a glass melting furnace with bubblers, heating electrodes, step and refining bench; Fig. 2 shows an enlarged section of Fig. 1; Fig. 3 shows a first variant of the subject as shown in Fig. 2, with bubblers, heating electrodes and refining bench but with no step; Fig. 4 shows a second variant of the subject as shown in Fig. 2, with heating electrodes, step and refining bench but with no bubblers; Fig. 5 shows a third variant of the subject as shown in Fig. 2, with bubblers, step and refining bench, but with no heating electrodes; Fig. 6 shows a partial longitudinal section through a fourth variant of the subject as shown in Fig. 2, with bubblers, step and refining bench, and with heating electrodes on the step, and Fig.7 shows a partial longitudinal section through a fifth variant of the subject as shown in Fig. 2, with no bubblers but with a step and refining bench, and with horizontal heating electrodes above the step. Fig. 1 shows a longitudinal section through a glass melting furnace 1, which has -beginning at a charging end 2 with a charging opening 2a - a melting zone 3, with two sections 3a and 3b, a refining bench 4 and a homogenization zone 5, and which ends at an offtake end 6 with an overflow 6a, which are followed by subsequent stages of processing (not shown). The centre of the melting zone is indicated by a dotted line "M". On the other side of this centre "M." are positioned the means described for the creation of the upward current in the glass melt. In the melting zone 3, and between its sections 3a and 3b, there is a first protective radiation barrier 7, and between the melting zone 3 and the refining zone 4 there is a second protective radiation barrier 8. Both barriers 7 and 8 have bottom edges 7 7a and 8a, which leave spaces "D" open above the melt surface 9 of the glass melt 10; these spaces must not necessarily be the same size. The spaces "D" form flow channels 7b and 8b for the backflow of combustion gases. There are no gaps at the connection to the furnace roof 1a. Burners 11, which generate horizontal flames, are arranged in pairs opposite each other in section 3a, and burners 1 la are arranged in the refining zone 4; the number and spatial arrangement of these is not restricted to that shown in Fig. 1. The hot combustion gases from the burners 11 and 1la flow through the channel 7b, and partly also through the channel 8b, in the direction shown by the arrows towards a flue 12. In the melting zone 3 there is charging material 13 on top of the melt surface 9, the volume of which material per unit of surface area decreases as a result of the melting process as it moves towards the protective barrier 8. This melting process is carried out from above by means of the hot gases from the burners 11 and 11 a, and may be -but need not necessarily be - assisted in section 3a by electrodes 14 in the floor area. The operation of the electrodes 14 can also be carried out for limited periods, e.g. for initial heating up. In the area of the protective radiation barrier 8 there are - in or above the tank floor 15 - a row of bubblers 16, a step 17 with a row of heating electrodes 18, and a refining bench 19. The length "L" of the refining bench 19 is proportionate to the flow speed of the glass melt and to the required length of time the melt has to remain on the refining bench, and is also dependent on the temperature and/or on the composition of the glass (e.g. high- or low-melting glass, vaporization characteristics of components with a low boiling point, etc). The bubblers 16, the step 17 and/or the heating electrodes 18 are all means of creating an upward current of the glass within the glass melt l0 towards the counterflow of the combustion gases below the second protective barrier 8 and towards the refining zone 19. 8 The same reference numbers are used in Fig. 2. The step 17, which rises up from the tank floor 15, extends across the entire width of the tank floor 15, and is of a height "H1", which is between 25% and 75% of the height "H2" of the refining bench 19 from the tank floor 15. Its right-angled edge, pointing upstream, extends to below the front edge 8e of the second protective barrier 8. The flow components which are thus caused are indicated by arrows. As already stated, the expression "beneath the protective radiation barrier" does not necessarily mean a location within the vertical projection of the barrier 8 on to the tank floor 15 or on to the step 17. Instead, the definition includes the possibility that the "means" of creating an upward current in the glass melt, as specified, can also extend upstream and downstream of the said second barrier 8, depending on the requirements of the optimum spacing of the components of these "means". In the embodiment shown in Fig. 3, the step has been omitted, i.e. the means of creating the upward current of the glass consist, in this case, of a row of bubblers 16 and heating electrodes 18, which are arranged in the tank floor and which are positioned in front of the vertical front face 19a of the refining bench 19. The flow components thus created are indicated by arrows. In the embodiment shown in Fig. 4, the row of bubblers has been omitted, i.e. the means of creating the upward current of the glass consist, in this case, of the step 17 with a row of heating electrodes 18, which are arranged on the step 17 and in front of the vertical front face 19a of the refining bench 19, the height of which bench is reduced by the step 17. The flow components thus created are indicated by arrows. In the embodiment shown in Fig. 5, the row of heating electrodes has been omitted, i.e. the means of creating the upward current of the glass consist, in this case, of the step.17 with a row of bubblers 16; which are arranged in the step 17 and in front of the vertical front face 19a of the refining bench 19, the height of which bench is reduced by the step 17. The flow components thus created are indicated by arrows. As already described, the subject of the invention causes a surface backflow of hot glass melt from the area of the bubblers and/or electrodes towards the charging end 2, 9 directly below the charging material, which is moving in the opposite direction. This causes the charging material to be heated very effectively from both sides: from above by the counterflow of the hot combustion gases, and from below by the counterflow of hot glass melt. This ensures that no unmelted material - either glass batch or refuse glass, or a mixture - reaches the refining zone. Fig. 6 shows another variant, in which the protective barrier 8, which is fitted with a cooling device 8c, is submerged in the glass melt 10, leaving open below its bottom edge several horizontal gap-like flow openings 8d, which are distributed evenly across the entire width of the tank, interspersed with supports. As in the examples described earlier, the overall flow of the glass is from left to right "downstream", and the overall flow of the combustion gases is from right to left, i.e. "upstream" in relation to the glass flow. Here, also, a step 17 is positioned in front of the refining bench 19 in the refining zone 4, beneath the barrier 8 and rising up from the tank floor 15, and in front of this step there is a row of bubblers 16 running at right angles to the tank. This causes the formation, on both sides of and within a bubble curtain 16a, of a superimposed upward current of the roller type as indicated by the arrows shown at this point. This causes an upstream flow component - i.e. towards the charging end, not shown here -which heats the charging material 13 from below, but at the same time prevents the material from crossing the bubbler area. Any possible backflows in the tank floor area are indicated by the dotted arrows. An upward flow of the glass melt 10 is also created by the front face 17a of the step 17, which front face is, in this case, sloping. Between the submerged part of the protective barrier 8 and the front face of the refining bench 19, a vertical gap 20 is formed, which likewise extends across the full width of the tank, and in which there is a row of heating electrodes 18 at right angles to the tank. These augment the upward current of the glass melt 10, as indicated by the flow arrows shown at this point. This prevents a backflow of the refined glass melt 10 from the refining zone 4 into the melting zone 3, i.e. it prevents already-refined glass melt, which has the highest temperature above the refining bench 19, from being mixed with still unrefined, and relatively cooler, glass melt. 10 The combustion gases from the burners 1 la in the refining zone 4, of which burners only one is shown, flow in this case through an upper flow channel 21, approximately in the direction of the arrow 22, and join up in the melting zone 3 with the combustion gases from the burners 11 in that zone. The full volume of the combustion gases thus provides additional heat from above to the charging material 13, although it must be admitted that the predominant source of the heating from above of the melt and/or the charging material is the gas radiation from the burner flames. In this case, the combined effects of bubblers 16, step 17, electrodes 18, barrier 8 and front face of the refining bench 19 bring about a distinct separation of the processes in the melting zone and the refining zone; moreover, the energy of the radiant heat is concentrated by the protective radiation barrier 8 in the refining zone 4 and the homogenizing zone 5. Fig. 7 shows yet another variant, in which the protective barrier 8 is not submerged in the glass melt but terminates in a curved bottom edge 8a above the melt surface 9, leaving free a flow channel 8b for part of the combustion gases from the refining zone 4 and the homogenization zone 5. As in the examples described earlier, the overall flow of the glass is from left to right "downstream", and that of the combustion gases from right to left, i.e. "upstream" in relation to the glass flow. Here, also, a step 17 which rises up from the tank floor 15 is positioned in front of the refining bench 19 below the barrier 8. Above the step are a number of electrodes 18, of which only one is visible and which - as shown in Fig. 7 - are arranged in pairs in the form of horizontal wall electrodes (perpendicular to the projection plane of the drawing); the electrodes can also rise vertically from the step (and parallel to the projection plane of the drawing, as shown in Fig. 6). This creates, on both sides of the electrodes, a superimposed roller-type upward current, as indicated by the arrows at this point. This causes, among other effects, an upstream (i.e. towards the charging end, not shown here) flow component, which heats the charging material 13 from below, but at the same time prevents the material from crossing the electrode area. An upward flow of the glass melt 10 is also caused by the front face 17a of the step 17, which front face is, in this case, vertical. 11 This also prevents any backflow of refined glass melt 10 from the refining zone 4 to the melting zone 3, i.e. it prevents already-refined glass melt, which has the highest temperature above the refining bench 19, from being mixed with still unrefined, and relatively cooler, glass melt. The combustion gases from the burners 1 la in the refining zone 4, of which only two are shown, additionally flow through an upper flow channel 21 approximately in the direction of the arrow 22, joining up in the melting zone 3 with the combustion gases from the burners 11 in that zone. The full volume of the combustion gases thus provides additional heat from above to the charging material, although it must be admitted that the heating from above of the glass melt and/or the charging material provided by the gas radiation from the burner flames is far greater than the convective heat transmission. In this case, the combined effects of the step 17, the electrodes 18, the protective barrier 8 and the front face 19a of the refining bench 19 bring about a distinct separation of the processes in the melting zone and the refining zone; moreover, the energy of the radiant heat is concentrated by the protective radiation barrier 8 in the refining zone 4 and the homogenizing zone 5. It is not strictly necessary for the burners 11 and 1 la to be arranged in pairs opposite each other.. They can also be arranged in an offset manner along the tank. 12 Reference numbers 1 glass melting furnace la furnace roof 2 charging end 2a charging opening 3 melting zone 3 a section 3b section 4 refining zone 5 homogenization zone 6 offtake end 6a overflow 7 first protective radiation barrier 7a bottom edge 7b flow channel 8 second protective radiation barrier 8a bottom edge 8b flow channel 8c cooling device 8d flow opening 8e front face 9 rnelt surface 10 glass melt 11 burner 11a burner 12 flue 13 charging material 14 electrodes 15 tank floor 16 bubbler 16a bubble curtain 17 step 17a front face 13 18 heating electrodes 19 refining bench 19a front face 20 gap 21 flow channel 22 arrow spaces "D" length "L" height "H1" height "H2" 14 WE CLAIM 1- Process for operating a glass melting furnace, in which a protective radiation barrier (8) is positioned between a melting zone (3) and a refining zone (4) with a refining bench ( 19): the barrier leaves open - above the melt surface (9) of the glass melt - at least one flow channel (8b,21) for the back flow of at least part of the combustion gases from the refining zone (4) into the melting zone (3), in which at least one upward current is produced in the glass melt (10) between the middle of the melting zone (3) and the front face (19a) of the refining bench (19) : this current is split - inside the glass melt (10) and before reaching the melt surface 2. Glass melting furnace having a melting tank with a tank floor (1S) and burners (11,11a) for at least partial heating by means of fossil fuels, in which are arranged - between a charging and (2) and a removal end (6) and in the direction of movement of the glass - a melting zone (3) having at least one extraction vent (12) for combustion glasses, a refining zone (4) having 15 burners (11a) and a refining bench (19) with a front face (19a) which protrudes from the base (15) of the tank, and a hoinogenizing zone (3), whereby - between the melting zone (3) and the refining zone (4) - a radiation protection barrier (8) is positioned in front of the latter, this barrier leaving open above the glass melt (10) at least one flow channel (8b,21) for a counterflow of the combustion gases from the refining zone (4) into the melting zone (3), in which means (16,17 18) are provided, between the middle of the melting zone (3) and the front face (19a) of the refining bench (19) in the direction of movement of the glass melt (10), which can produce an upward current of the glass melt (10) towards the malt surface (9) and - on the surface of the glass melt (10) - a) an upstream movement of the glass towards the charging end and b) a downstream movement towards the the refining bench (19). 3. Glass melting furnace as claimed in claim 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass melt (10) - are selected from the element combination of bubblers (16) in the flow of the tank (15) and a following step (17). 4. Glass melting furnace as claimed in claim 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass 16, melt (10) - are selected from the element combination of bubblers (16) and heating electrodes (18) in the floor tank (15) without a following step (17). 5- Glass melting furnace as claimed in claim 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass melt (10) - are selected from the element combination of bubblers (16) in the floor of the tank (15) and heating electrodes above a following step (17). 6. Glass melting furnace as claimed in claim 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass melt (10) - are selected from the element combination of a step (17) which is lower in height than the refining bench (19) and which reaches from the front face (19a) of same towards the charging end (2). 7. Glass melting furnace as claimed in 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass melt (10) - are selected from the element combination of step (17) with heating electrodes (18) arranged above it. 8. Glass melting furnace as claimed in claim 2, wherein the means for producing the upward current of the glass melt - at right angles to the process-determined overall flow of the glass 17. melt (10) - are selected from the element combination of step (17) with bubblers (18) arranged inside it. 9. Glass melting furnace as claimed in claim 2, wherein where a step (17) is used which is positioned in front of the front face (19a) of the refining bench (19) and which protrudes from the tank floor (15), the step a) aktends across the whole width of the tank floor (15) b) is of a height ("H1") which is between 25% and 75% of the height ("H2") of the refining bench (19) from the tank floor (15) c) Is positioned against the horizontal flow direction of the glass melt (10) and extends to beneath the radiation protection barrier (8). 10. Glass melting furnace as claimed in at least one of claims 2 to 9 wherein a further radiation protection barrier (7) is positioned within the melting zone (3) between the extraction vent (12) and the protection barrier (8) which is in front of the refining zone (4); this second barrier divides in the melting son(c) (3) into a first section (3a) containing the extraction vent (12) and a second section (3b), and has a lower edge (7a) which leaves free a flow channel (7b) above the furnace charge material (13) arid the glass melt (10) to permit a back flow of the combustion gases from the second auction (3b) to the first section (3a) and to the extraction vent (12), 18. 11• Glass melting furnace as claimed in claim 2, wherein the lower part of the radiation protection barrier (8) leaves free at least one flow channel (21), through which at least part of the combustion gases from the burners (11a) can pass from the refining zone (4) to the melting zone (3). 12. Glass melting furnace as claimed in claim 11, wherein the radiation protection barrier (8) has a lower edge (8a) which leaves free a flow channel (8b) immediately above the melt surface (9) through which at least part of the combustion gases from the burners (11a) can pass from the refining zone (4) to the melting zone (3). 13. Glass melting furnace as claimed in claim 11, wherein the lower edge (8a) of the radiation protection barrier (8) is immersed in the glass melt (10), leaving free, above the step (17) which protrudes from the tank floor (15), at least one gap-shaped flow opening (8d) for the glass melt. 14. Glass melting furnace as claimed in claim 13, wherein the radiation protection barrier (8) on the step (17) rests on at least one support, each of which is positioned between two flaw openings (8d) in such a way that the total width of all the flow openings (8d) is, as far as possible, the same as the width of . the tank floor (15) and that the flow openings (8d) are distributed evenly across this width. 19. 15. Glass melting furnace as claimed in claim 13, wherein there is a verticl gap (20) between the back of the radiation protection barrier (8) and the front face (19a) of the refining bench (19) to allow the throughflow of the glass melt (10), in which gap (20) are arranged at least two heating electrodes (18). Dated this 12th day of March 1999 OF L.S.DAVAR & CO APPLICANTS' A6ENT 20- The invention relates to a process for operating a glass melting furnace, in which a protective radiation barrier (8) is positioned between a melting zone (3) and a refining zone (4) with a refining bench (19); the barrier leaves open - above the melt surface (9) of the glass melt - at least one flow channel (8b,21) for the back flow of at least part of the combustion gases 0from the refining zone (4) into the melting zone (3) in which at least one upward current is produced in the glass melt (10) between the middle of the melting zone (3) and the front face (19a) of the refining bench (19); this current is split - inside the glass melt (10) and before reaching the melt surface (9) -into a first part-current moving upstream into the melting zone (3) and a second part-current moving downstream towards the refining bench (19), whereby the second - downstream - current prevents a back flow of glass melt (10) from the refining zone (4) into the melting zone (3).

Documents:

00214-cal-1999-abstract.pdf

00214-cal-1999-claims.pdf

00214-cal-1999-correspondence.pdf

00214-cal-1999-description(complete).pdf

00214-cal-1999-drawings.pdf

00214-cal-1999-form-1.pdf

00214-cal-1999-form-2.pdf

00214-cal-1999-form-3.pdf

00214-cal-1999-form-5.pdf

00214-cal-1999-p.a.pdf

00214-cal-1999-priority document others.pdf

00214-cal-1999-priority document.pdf

214-CAL-1999-FORM 27-1.1.pdf

214-CAL-1999-FORM 27.pdf

214-cal-1999-granted-abstract.pdf

214-cal-1999-granted-claims.pdf

214-cal-1999-granted-correspondence.pdf

214-cal-1999-granted-description (complete).pdf

214-cal-1999-granted-drawings.pdf

214-cal-1999-granted-examination report.pdf

214-cal-1999-granted-form 1.pdf

214-cal-1999-granted-form 2.pdf

214-cal-1999-granted-form 3.pdf

214-cal-1999-granted-form 5.pdf

214-cal-1999-granted-letter patent.pdf

214-cal-1999-granted-pa.pdf

214-cal-1999-granted-priority document.pdf

214-cal-1999-granted-reply to examination report.pdf

214-cal-1999-granted-specification.pdf

214-cal-1999-granted-translated copy of priority document.pdf