MXPA96001686A - Procedure and device for delvid fusion - Google Patents

Abstract

The present invention relates to a melting furnace for producing continuous flat glass, comprising: a) a glass melting compartment having an upstream wall, a downstream wall and opposite side walls connecting the upstream and downstream walls together below, the glass melting compartment adapted to contain a quantity of molten glass, has a top surface extending through the glass melting compartment, the glass melting compartment further having: i) an upstream part adjacent to the glass melting compartment; the upstream wall with at least one upstream supply opening located in the upstream part, and ii) a downstream part adjacent to the downstream wall and having a downstream opening for removing molten glass from the melting compartment of glass; b) at least one training compartment in communication with the downstream opening and connected to the wall downstream of the glass melting compartment to form flat glass: c) a charging device cooperating with at least one of the upstream supply openings for supplying vitrifiable material within the glass melting compartment; d) at least one burner located in a burner passage connected to a predetermined wall of the glass melting compartment for supplying fuel and fuel material to the glass melting compartment at a first level above the upper surface of the molten glass, the fuel requires additional fuel material than that supplied with the fuel in the burner to effect combustion thereof, to produce a flame directed along a path, and e) a plurality of oxygen lances located in oxygen passages connected to the wall; default of the glass melting compartment to supply oxygen in an ac nity of at least 80% of the combustible material necessary to effect combustion of carburan

Description

PROCEDURE AND DEVICE FOR THE FUSION OF GLASS DESCRIPTION The present invention relates to a method and a device for melting glass from vitrifiable materials, a device more commonly known as a melting furnace, for feeding, in continuous with molten glass, forming installations, either flat glass or laminate or float installations, either hollow glass or for glasses, as a plurality of forming machines, either glass for insulation (glass wool, rock wool), or glass for reinforcing fibers or also of special glasses for television screens or others. The invention relates to all types of melting furnaces, which involve production capacities of molten glass which can be counted for example by extruded 10 tons per day, up to 1000 tons per day and more. This type of furnace is customarily composed, in a known manner, of a succession of compartments that flow into each other and each having specific functions and dimensions. Indeed, the furnace must be able to melt vitrifiable materials and ensure the chemical and thermal homogeneity of the glass once it is melted. Ovens can be classified into two broad categories according to the heating medium adopted to melt the vitrifiable materials in the melting compartment: On the one hand, there are electric melting furnaces, called "cold vaults", where the melting is carried out by electrodes that are submerged in the depth of the molten glass, which is known for example by EP-BO 304 371. On the other hand, there are flame ovens, also known as generator ovens, especially known from the US patent. -4,599, 100. In this case, the heating power is provided by two rows of burners that generally operate with a fuel / air mixture, and in alternation; the combustion gases then alternately heat the first and the second of two generators placed in front and on one side and on the other side of the fusion compartment and in communication with it. The combustion gases are thermally terminated through the refractory piles that constitute those refractory generators that then restore the stored heat to the melting compartment. This mode of heating is effective and widely used, although not devoid of certain drawbacks that are inherent. In this way, the energy cost - of the combus-tibie / air burners is relatively high. On the other hand, the operating system of the burners that are "activated" in alternation with cycles of the order of 15 to 60 minutes, is not the simplest to control rigorously and can cause a discontinuity in a continuous production and balance of temperatures is affected by that condition. Its use also leads to introduce a significant amount of air, therefore nitrogen, into the melting compartment, so there is no doubt that the risk of forming a quantity of NO? that will then have to be treated. In addition, the significant amount of special and expensive refractories needed to manufacture regenerators, significantly increases the cost of construction of the furnace. The object of the invention is therefore that of reducing the drawbacks linked to the use of furnaces of flames, proposing a new type of flame heating that greatly reduces the energy cost and the cost of building materials of the furnace, which simplifies the operation mode, guaranteeing at the same time a molten glass of a quality at least as high. Another object of the invention is to reduce the wear of the refractories constituting the walls of the furnace and that of increasing the duration of the furnace., that way. The invention relates to a furnace for the melting of vitrifiable materials, an oven comprising a melting (or fusion / tuning) compartment of the glass provided, at the rear, with at least one opening intended to be fed with vitrifiable materials with the help of devices for introduction into the oven, arranged in front of that opening. In the front part, this melting compartment comprises at least one outlet opening of the molten glass which opens into one or more front compartments intended to convey the molten glass towards the forming zone. According to the invention, the melting of the vitrifiable materials is ensured in the melting compartment, essentially, by means of at least one fuel and / or gas burner.; the oxidizer is formed mostly by pure oxygen, at least 50% of the comburent needed for the desired combustion, and therefore is brought separately by at least one oxygen nozzle. By practically pure, it is understood according to the invention, oxygen of at least 80% and preferably of at least 9.0%. By separate, separate arrival points are understood for the fuel and / or gas, on the one hand, and for oxygen, on the other hand. In the context of the invention, the terms "rear" and "front" refer to the overall direction of a flow of the molten glass through the furnace. By melting compartment, it is meant both the melting compartment and the melting / refining compartment. The selection of a heating mode according to the invention, which combines burners and oxygen nozzles that bring at least 50% of the oxygen separately, has a number of advantages in relation to conventional burners, which mainly operate with an air type comburent, or also in relation to oxygen burners fed with oxygen in stoichiometric quantity. This heating mode with oxygen, authorizes first, the abandonment of operation in traditional "inversion" of the flame ovens; Oxygen burners can keep a steady operating regime over time, which makes the use of the furnace easier; This continuous operation is more regular and authorizes much finer regulations than with an operation in investment. Above all, the presence of regenerators made from refractory piles and that can be worn away can be completely suppressed. In this way, oxygen burners can heat the vault of the fusion compartment and the volume called "laboratory" between that vault and the n.vel of molten glass, continuously and without having to resort to regenerators. The atmosphere that reigns above the level of the glass in the fusion compartment is much more stable and controlled, which may prove important to produce so-called special glasses. On the other hand, the thermal performance of this type of burners, is significantly higher than that of conventional burners that work with an air type comburent, due to the absence of nitrogen that significantly reduces the volume of smoke generated . In this way, considerable reductions in energy costs are obtained globally, and this type of burner also allows for sensible increases in the specific output of the furnace.

The fact that the burners selected according to the invention introduce a very small, even nil amount of air into the melting / refining compartment, very strongly reduces the possibilities of formation of contaminating gases of the N0? Type, causing at least one lowest cost, of treatment of combustion gases evacuated outside the compartment. In addition, always in relation to conventional burners, the oxygen burners allow to introduce into the melting compartment, a volume of gas much less important and therefore, the volume of gas resulting from combustion, also decreases strongly as already indicated . This means that we can consider reducing the so-called "laboratory" volume mentioned above, especially for example by lowering the vault of the fusion compartment a little, which, here too, tends to reduce at the same time the energy cost and the construction cost of the furnace itself. Therefore, everything in the use of oxygen burners that work without investment, contributes to the obtaining of a more reliable oven, less expensive in its concept and that allows energy savings that can go up to widely of 15% in relation to a conventional flame oven of similar dimensions.

However, when practically pure oxygen is used as an oxidizer in fuel and / or gas burners with so-called stoichiometric amounts, the flame temperature obtained at the level of the burner outlet is higher than the temperature of flame that uses air as an oxidizer. Then, a rapid deterioration of the refractories constituting the walls of the furnace, especially around the nose of the burners, can occur. Therefore, an object of the invention is a process for the melting of the vitrifiable materials in a melting compartment, to feed continuously with molten glass, the glass formation facilities, in which the fusion of the vitrifiable matters is ensured by the combustion of a mixture of fuel and / or gas with practically pure oxygen; the supply of fuel and / or gas in the melting compartment is effected in at least one point with a lack of oxygen in relation to the stoichiometric qualities; at least 50% of the oxygen that corresponds to the total combustion is brought separately in at least one different arrival point. This contribution of at least 50% of the oxygen necessary for the total combustion at least one different arrival point and preferably for several different arrival points, also provides a greater flexibility of regulation of the temperatures in the melting compartment; the o. the zones of the compartment where the oxygen is brought, generally corresponds to some points from which the thermal level is to be controlled. Furthermore, the feeding of the burners with lack of oxygen according to the invention, and the oxygen supply, in combination, by judiciously distributed oxygen nozzles, allows above all to have a controlled flame temperature called "low temperature, low flame". NO?) In addition, the fact of intercalating oxygen between the flame and the walls of the furnace, ensures an oxidizing atmosphere at the level of the walls.The flame is also far from the walls and thus the phenomenon of exudation and attack is diminished. The combination of the oxygen burners fed with lack of oxygen and the oxygen nozzles, provides a better distribution of the flame over the composition and the glass baffle. flame, it allows to lower the temperatures of the vault and to raise the temperatures of hearth.Finally, this allows to consider also increases of the saccade of the hor from 10% to 30%, as indicated above, the supply of oxygen by the burnerson the one hand, and oxygen nozzles, on the other hand, is therefore made at a rate of 0% to 50% only for burners and the complement to 100% of the oxygen necessary for combustion, is made by the oxygen nozzles. Preferably, the oxygen supply is made at a rate of at least 80% separately by the oxygen nozzles. Finally, all the oxygen or practically all the oxygen can advantageously be provided separately. In this way, any incident at the level of the nose of the injector (burner) is avoided in case of soiling or spills, in particular in the case of special glasses. For everything, or practically for all oxygen, it is understood from 100% to 95% approximately of oxygen. According to a feature of the invention, the flame of a burner is supplied by means of oxygen contributions to the flame and at certain places in the furnace, in order to have the desired flame temperature. However, the very favorable result mentioned above would be understood if, contrary to the invention, the entry of air into the fusion compartment coming from the front compartments is not prevented. Otherwise, one is exposed to the risk of re-creating a certain amount of N0X-type pollutant gases in the melting compartment and the economy on the energy level is significantly reduced at the level of that compartment. This arrival of air can be prevented, with the aid of sealing means in relation to the gases of the melting / tuning compartment in relation to the rest of the furnace. This or these sealing means "isolate" in this way, the atmosphere that prevails above the molten glass in the fusion compartment, of the atmosphere of the adjacent successive compartments or front compartments. These "front" compartments are used to condition the glass, that is to say, they are practically intended to gradually cool it to reach its formation temperature, to improve or even to improve its chemical and thermal homogeneity and to eliminate it, the foreign bodies of the type non-melted or particles of refractory material. This thermal conditioning can be carried out in one or the other of those so-called front compartments, in a known way; the alternative or combined use of the heating means, for example conventional fuel / air burners, and cooling means, introduce the air in a large quantity at room temperature in those compartments. Therefore, it is necessary to prevent these types of gases from "going back up" into the melting / tuning compartment, so as not to disturb their very controlled atmosphere. Of course, if the front compartment or compartments are designed, for example, in order to use cooling means without introducing air, and in presenting an atmosphere not composed of air, those means for returning sealed, no longer seem to be indispensable. According to an embodiment of the device according to the invention, the burners or injectors are distributed in alternating lines with the oxygen nozzles in the rear sprocket and / or the front sprocket, and / or the side walls parallel to the glass bath with a number and an inclination of + 5 ° to -15 °, depending on the structure and dimensions of the oven, and the position in relation to the glass bath. The oxygen burners open into the melting / tuning compartment through the over-structure walls whose sections can be very small and do not alter the thermal insulation of the assembly. The burners can be independent or associated in groups of burners whose heating power is regulated independently from one group to the other. The groups are arranged practically perpendicular to the axis of the furnace on the walls and practically parallel to the furnace on the front or rear front walls, with the possibility each time of orientation from 0 to 20 ° in relation to those axes and to the horizontal plane. The heating can be optimally modulated and regulated in any melting / tuning compartment and reach all desired temperature profiles, depending on the types of molten glass and manufacturing. Of course, other arrangements and oxygen nozzles are possible. Provision can be made in the melting / tuning compartment for mechanical means of the boiler type for accelerating convection or auxiliary heating means of the electrode type immersed in the glass in order to adjust or correct the temperature profile. The fact of having deleted the recuperator or the regenerators, reduces the number of openings, frees the access and the place around the furnace, which allows to isolate it better and facilitates its maintenance. In order to fully recover the thermal units of the fumes that come from the combustion of the burners in the melting compartment, the evacuation openings are preferably placed behind the feed openings with vitrifiable materials; the fumes then follow a trajectory from the center of the oven towards the walls (making a screen between the flame and the walls), to return from front to back, to penetrate above the entrance area to the furnace where the vitrifiable materials supernate they can advantageously be preheated in this way. Several placements can be adapted for the feed opening (s) with vitrifiable materials. These can be practiced, on the one hand, on one or both side walls and, on the other hand, on the front wall of the fusion compartment. An advantageous solution can be two symmetrical openings in front of one or the other of the side walls. It is possible to provide smoke evacuation openings, either in the rear front wall, or in the side walls of the fusion / tuning laboratory. Once they have left the furnace laboratory, these fumes are still relatively hot and it can be foreseen to take them in devices for recovering heat or preheating the vitrifiable materials before they are introduced into the furnace. These fumes can also serve to preheat oxygen.

Another advantage of the invention that uses the combination of burners (or injectors) of gas and / or fuel, fed with lack of oxygen, this lack can be total, and with oxygen nozzles, is a more flexible regulation of the flame and above all a regulation of its position in relation to the glass composition; the flame is attracted to the place of oxygen supply. This advantage makes it possible in particular to design variants of the device according to the invention in the arrangement of burners and oxygen nozzles. By separate oxygen supply, it is generally understood according to the invention, an oxygen supply at one or several points distant from at least 5 cm and preferably at least 10 cm from the point of contribution of the fuel and / or gas, is say of the nose of the burner. The oxygen can advantageously be brought to two points arranged around each burner, and preferably at a level below the level of the arrival of the fuel and / or gas. In this way, the invention also provides an assembly that can be used in the heating system combining a burner with oxygen nozzles, according to the invention. This assembly comprises a refractory block provided with a passage for housing a burner; this passage is flared mainly in the form of a truncated cone, towards the face intended to be oriented towards the inside of the oven, and with two passages arranged at equal distances and more than 5 cm and preferably more than 10 cm from the axis of the burner; those two passages that are intended for the accommodation of the two nozzles are also located at a level below the level of the burner. The assembly can be equipped with a burner and the two oxygen nozzles. This arrangement of the oxygen nozzles in relation to the burner, allows a very good regulation of the flame, while avoiding, above all, an exaggerated over-heating of the refractory in the place of the nose of the burner. Other features and advantages of the invention will become apparent in the description below with the help of the figures that they represent: Figure 1: a longitudinal sectional view of an oven according to the invention; Figure 2: a plan view of that furnace; Figure 3: a possible operation of an oven according to the invention; Figures 4 and 5: an assembly comprising a refractory block and a burner / oxygen nozzle combination, according to the invention.

Figures 1 and 2 schematically represent the fusion / tuning compartment 1 of the melting furnace according to the invention. That compartment is delimited by a hearth 2, a vault 3, rear walls 4, front 5 and sides 6 and 7. The level of the molten glass is indicated in figure 1 with the horizontal line X. The glass flows towards the front compartment by the narrow passage 18. This furnace comprises 2 main areas: - the melting zone 8 where the vitrifiable materials 9 which superimpose on the molten glass are introduced; - melting / tuning zone 10: this zone is delimited by a lower vault 3, which allows above all a refractory gain. In zone 8, a lateral introduction of the vitrifiable mixture is provided in this embodiment. Of course, other embodiments according to the invention may be used such as a front introduction mode. The feeding opening shown in FIGS. 1 and 2 is constituted by two symmetrical openings 11 and 12 connecting the melting compartment to two appendices 19 and 20, in which the change of vitrifiable material is effected, on both sides, in this example.

The openings 13 and 14 are provided for the evacuation of the combustion fumes, behind the feed openings 11 and 12. In this way, the fumes are forced to follow an evacuation path from the center of the furnace, going along the walls and the vault and passing above the vitrifiable materials not yet melted, which improves the energy efficiency of the oven. The fumes can then be used to feed any heat recovery device, or in a pre-heating system for vitrifiable materials. It is also possible to provide auxiliary openings 16 for evacuating the fumes in the front and side walls. In all the walls, front, side, front, there are small openings to introduce the injectors 15 or burners that are represented in the figures with an arrow in solid lines, and the oxygen nozzles 17 that are represented with an arrow in lines discontinuous The burners and oxygen nozzles are arranged above the level of the glass, so as to form groups, or individually to mark a hot spot, and reach an optimal distribution of heat exchange between the flames and the glass bath; Each group of independent burners can be regulated in heating power independently, which allows to obtain the desired temperature profile at any point and at any time. On the other hand, the oxygen nozzles are arranged in various places on the walls in order to accompany the flame and to act in such a way that, over the path of the flames, there is no over-oxygenation which gives a too hot flame, or on the contrary there is no lack of oxygen that gives a reductive flame. In fact, in both cases, premature wear of the tower refractories can occur. The use of burners and oxygen nozzles that work continuously, ensures a thermal performance significantly higher than that of conventional burners, using a reduced volume of comburent in relation to air, which gives a reduced volume of smoke of 80% approximately. The concept of the fusion / tuning laboratory can be reduced in volume, without counter-indication for the operation of the furnace, which results in an economy of construction materials of the furnace. Also, the burners and oxygen nozzles do not introduce air, therefore they do not introduce nitrogen into the furnace, which prevents the formation of NO type? The oxygen supply of the burners separately, avoids a deterioration of the refractories especially at the level of the nose of the burners. To guarantee the advantages of any oxygen, it is necessary to eliminate any introduction of air into the fusion / tuning compartment. It is necessary that all openings between the laboratory and the exterior are closed (expansion joints, registers or hatches, etc.). In addition, the exit (s) of the glass from the fusion / tuning compartment, towards the training compartments, are made in such a way that there are no recirculating belts of the molten glass between the melting / tuning zones and the feeding zones of the working compartments, nor an exchange of atmosphere. To do this, known feeding means are used: throat and channel feed, channel feed with suspended or submerged barrier, channel feed with suspended screen and barrier. The heating system according to the invention makes the exploitation of the furnace more reliable with a lower manufacturing cost. It seeks a constancy of the atmosphere of the fusion compartment which, with suitable refractories, allows to increase the life of the furnace. In fact, thermal variations are one of the causes of refractory wear. On the other hand, air pollution decreases very significantly. Thus, for example, the heating system according to the invention allows the furnace vault temperature to be lowered, from approximately 50 ° C to 80 ° C and to increase its hearth temperature from about 10 ° C to about 20 ° C, in relation to the known systems for a given melting temperature. In addition, the temperature at the level of the nose of an oxygen burner decreases approximately 60 ° C, thanks to the separate supply of oxygen. Figure 3 schematically represents the operation of a heating system according to the invention, for a circuit furnace. A burner 21 fed with fuel and / or gas, but practically without oxygen, is arranged in the rear sprocket 22 of the furnace 23. A part of the oxygen necessary for combustion is brought by the oxygen nozzles 24 arranged around the burner 21 on the rear sprocket. The amount of oxygen brought by these two nozzles corresponds to approximately 20% to 40% of the oxygen needed for combustion. Other oxygen nozzles 25 are arranged in the walls of the furnace. Four pairs of nozzles 25 are represented here. Each of those pairs brings approximately 15% to 20% of the oxygen needed. That way, the oxygen is brought accompanying the flame 26 along its route, so as to have a flame, neither too hot, nor too cold. When it is desired to increase the draft of the furnace, other burners 27 can be placed between the pairs of oxygen nozzles 25 and also increase the oxygen supply by those nozzles and / or by other supplementary nozzles. The molten glass is evacuated through the outlet 42 to the front compartment. Figures 4 and 5 represent an assembly 28 which is advantageously used for the heating according to the invention, combining a burner and oxygen nozzles. This assembly comprises a refractory block 29 provided with a central passage 30 which ends up elongating in the shape of a truncated cone 31 whose axis 32 is inclined approximately 15 ° downwards in relation to the horizontal. That passage 30 flared toward the face 41 which is intended to be oriented towards the interior of the honor, extends the opening 33 provided in a composite plate 34 for mounting the burner 35 (not shown in figure 5) with the help of a cylindrical sleeve 36 .

Other passages 37 are provided which are arranged symmetrically, under the axis of the burner, and outside the truncated cone 31, for assembly with the help of cylindrical sleeves 38 of two oxygen nozzles (not shown). The axes of these two passages 37 are located at a distance greater than 10 cm from the axis 39 of the nose of the burner 35. Fixing means 40 are provided for fixing the composite plate 34 on the refractory block 29. This heating assembly Above all, it allows a very good regulation of the flame temperature, neither too hot nor too cold. In particular, it prevents the nose of the burner from getting dirty, and also prevents rapid deterioration of the refractory near the nose of the burner.

Claims (13)

1. NOVELTY OF THE INVENTION Having described the invention, we consider it as a novelty and, therefore, claim as our property, what is contained in the following clauses. 1. Furnace for fusing vitrifiable materials comprising a glass melting compartment; at its rear part, the compartment is provided with an opening intended to be fed with vitrifiable materials with the help of an introduction device placed in front, and in the front of an outlet opening of the molten glass that opens into a compartment a front that is intended to conduct the molten glass towards the formation zone, characterized in that the fusion of the vitrifiable materials is ensured in the fusion compartment, for the essential part, by at least one fuel and / or gas burner; the oxidizer is formed mostly by practically pure oxygen; at least 50% of the oxygen required for the desired combustion is brought separately by at least one oxygen nozzle.
2. 2. Furnace according to clause 1, characterized in that at least 80% of the oxygen necessary for combustion is brought separately.
3. 3. Oven according to clauses 1 or 2, characterized in that all or practically all the oxygen is brought separately by means of at least one oxygen nozzle and preferably by several oxygen nozzles arranged on the path of the flame.
4. 4. Furnace according to any of clauses 1 to 3, characterized in that it is equipped with at least one means for making the part between the fusion compartment and the front compartment watertight in relation to the gases.
5. 5. Furnace according to any of clauses 1 to 4, characterized in that at least a part of the burners is distributed in relation to two rows, which open into the melting compartment through the side walls thereof, being alternated with oxygen nozzles.
6. 6. Furnace according to any of clauses 1 to 5, characterized in that the burners are divided into a plurality of groups whose heating power is regulated autonomously from one group to the other.
7. 7. Furnace according to any of clauses 1 to 6, characterized in that heating means are provided in the melting compartment, especially in the form of electrodes submerged in the depth of the molten glass.
8. 8.- Procedure for fusing vitrifiable matter in a melting compartment, to feed continuously with molten glass, in glass formation facilities, in which the fusion of the vitrifiable materials is ensured by the essential, by the combustion of a mixture of fuel - and / or gas with practically pure oxygen, characterized in that the supply of fuel and / or gas in the melting compartment is effected at least one point of arrival with a lack of oxygen in relation to the desired quantities that correspond practically to the stoichiometric quantities and total combustion; at least 50% of the oxygen that corresponds to the total combustion is brought, separately at least at a different point of arrival.
9. 9. Procedure according to clause 8, characterized in that at least 80% of the oxygen is brought separately.
10. 10. Process according to any of clauses 8 or 9, characterized in that all or practically all the oxygen is brought separately, preferably at several points of arrival.
11. 11.- Procedure according to any of clauses 8 to 10, characterized in that the temperatures and the position of the zones from which it is desired to control the thermal level in the melting compartment, by a contribution separately, by a part, of the essential oxygen necessary for combustion and, on the other hand, fuel and / or gas.
12. 12. Method according to any of clauses 8 to 11, characterized in that the flame of a burner is fed, by means of successive contributions and at different points, with the oxygen necessary for combustion.
13. 13.- Heating assembly equipped or not with a burner and oxygen nozzles, which can be used for the implementation of the procedure according to any of clauses 8 to 12, characterized in that it comprises a refractory block 28 provided with a passage 30 that corresponds to the housing of a burner; that passage is flared towards the face 41 which is intended to be oriented towards the interior of the oven, and of two passages 37 for receiving oxygen nozzles arranged outside the flared passageway 30, for the burner and at a level below the axis of that passage .