WO2025238036A1 - Device for producing a glass melt - Google Patents

Abstract

In the device, following an inlet region (1) is arranged in a housing (6), said inlet region being inclined downwards at least partially vertically obliquely in the horizontal direction and being adjoined by a melting region (5) and with a refining region (7) adjoining same. The melting region (5) and the refining region (7) are inclined obliquely downwards in the horizontal direction starting from the inlet region (1). The formed glass melt flows to a bottom outlet (4) as a result of gravitational force. In order to melt the mixture fed into the inlet region (1), at least one microwave source (2) is arranged above the melting region (5) and emits microwaves in the direction of the mixture discharged through the inlet region (1) and the melting region (5). At least one plasma source (3) is arranged on the housing (6) and is oriented in such a way that the glass melt formed in the melting region (5) can be refined to a sufficient extent in the refining region (7) with the plasma and at least one plasma torch formed therewith.

Description

Device for producing a glass melt

The invention relates to a device for producing a glass melt, wherein the glass melt produced in this way can have different consistencies for various types of glass up to and including glass ceramics.

Melting inorganic raw materials, especially in glassmaking, is an energy- and time-consuming process. The traditional radiation-based transfer of the necessary energy into the material-

The melting capacity of a given mixture is small due to the material properties of the raw materials (low thermal conductivity). This means that the material melts very slowly. Conventionally, the melting capacity can therefore only be increased with considerable effort. The invention aims to reduce the time and energy required for melting the raw materials.

At the same time, the refining process, i.e., the expulsion of dissolved gases or bubbles, in the molten glass is also a very slow process, influenced by the redox conditions, the temperature-dependent viscosity, and the solubility of gases. This refining process should also be accelerated. Overall, the amount of energy required to sufficiently melt the respective glass melt should be reduced.

Conventional inclined bed melters are typically heated either by gas burners or electric heating elements. Due to the radiative heat transfer, the melting process is very slow. Atmosphere control is not possible with gas burners, while with purely electric heating, the furnace chamber can be additionally gassed to create a defined atmosphere.

The melting capacity in conventional systems is comparatively low, as it is limited by heat transfer. With gas-heated systems, both flame temperature control and atmosphere control are only possible to a limited extent. Purely electrically heated systems (with heating elements made of, for example, molybdenum disilicide) exhibit a very low melting capacity due to the maximum surface load on the heating elements. Additionally, energy consumption is higher in conventional systems because very high temperatures must already be present in the melting zone.

It is therefore an object of the invention to provide possibilities for the production of glass melts with which a reduction in energy consumption, a reduction in melting time, a reduction in refining time and a reduction in refractory wear can be achieved by reducing the wall temperature and, if possible, also a consistently high glass quality. are reachable.

According to the invention, this problem is solved with a device having the features of claim 1. Advantageous embodiments and configurations can be realized with features contained in dependent claims.

In the device according to the invention for producing a glass melt, a housing contains an inlet area for the mixture that is inclined at least partially vertically downwards in a horizontal direction, to which a melting area and a refining area are connected, wherein the melting area and the refining area are also inclined downwards in a horizontal direction starting from the inlet area and are lined with refractory material, so that the formed glass melt flows due to gravity to a bottom outlet for finished molten glass, and at least one microwave source is arranged above the melting area to melt the mixture introduced into the inlet area, which directs microwaves in the direction of the mixture introduced through the inlet area and the melting area.

Furthermore, at least one plasma source is arranged on the housing and aligned in such a way that the glass melt formed in the melting area can be sufficiently purified in the refining area with the plasma and at least one plasma torch formed therewith.

At least one microwave plasma source can be used as the plasma source(s). Alternatively, at least one arc plasma source can also be used. In any case, a plasma gas is supplied, which can be oxygen, nitrogen, a noble gas, or a gas mixture that may also contain air.

Pure microwave sources that can be used for heating in the melting range should have sufficiently high power to safely melt the glass mixture, bring it to the target temperature, and compensate for energy losses to the environment. Plasma sources used for energy supply in the lautering area should have sufficiently high power to set the lautering temperatures required for the glass types used, to compensate for the required flow viscosity and the energy losses of the device in the lautering area.

The inlet area should be inclined at an angle that ensures the introduced mixture reaches the melting zone in such a way that the mixture has a maximum thickness sufficient for reliable melting using microwave energy. An angle in the range of 40° to 70° can be selected. The required mixture thickness at the entrance to the melting zone can also be achieved through the inlet itself, through which the mixture is introduced. Appropriate dimensions and gap width can be used for this purpose.

The usual raw materials and also crushed waste glass can be used as a mixture, which can be supplied in a form known from the prior art.

To achieve the most uniform possible feed of the mixture through the inlet area into the melting area, vibrations, for example by using a vibrator, can be used to provide support.

The angle at which the melting and lautering area should be inclined relative to the horizontal is significantly smaller than the angle of inclination of the inlet area. It can have a generally accepted value.

By combining the technologies of "microwave-assisted melting of the raw materials" and "high-temperature plasma torch" with a device known as an "inclined bed melter," the melting process can be accelerated, since microwaves can heat the mixture from the inside out. The energy transfer to the mixture is essentially limited only by the power of the microwave source and can be several orders of magnitude greater than with conventional methods.

By using one or more plasma torches, the temperature in the The temperature in the lautering zone can be continuously regulated while simultaneously controlling the gas composition. This allows for a reduction in lautering time and an improvement in glass quality. The heating technologies mentioned can be supplemented in both the melting and lautering zones by conventional heating methods, such as electric heating using SiC heating rods or gas heating.

Because high furnace temperatures are not necessary in the melting area, the energy consumption of the plant can be reduced compared to conventional plants.

The core of the invention lies in the combination of the three features "inclined bed melter", melting of glass mixtures with microwaves and plasma torch for refining.

By combining microwave and plasma torch heating, significantly faster heating and better atmosphere control can be achieved compared to current technology. In particular, the plasma torch allows for the targeted introduction of gases, vaporized liquids, or particles, thus influencing the glass properties. Furthermore, the proposed technology eliminates the need for a melting tank, thereby accelerating the refining process compared to current methods.

The invention enables a separation between the melting area with microwaves and the refining area with plasma torch(s), thereby allowing targeted application of energy according to energy form.

An inclined bed melter within the meaning of this invention is a furnace formed with a housing and an internal structure that forms a furnace chamber separated from the surroundings by walls, in which energy transfer takes place, in which the raw materials forming the respective mixture or at least partially a glass mixture can be continuously heated and melted.

The oven chamber is conveniently divided into two areas. Solutions A single, continuous furnace chamber or multiple compartments are also conceivable. The melting process takes place in one compartment, while purification and conditioning occur in another. At least one compartment of the apparatus is mounted or tilted horizontally, and it is advantageous to be able to tilt the plasma source(s) and the microwave source(s) simultaneously. The two compartments can be atmospherically separated by a movable and height-adjustable skimmer made of a suitable material (e.g., AZS). A permanently installed separation is also conceivable.

The melting area is primarily supplied with heat energy by one or more microwave sources and should be large enough to allow a microwave port (for example, in the form of a waveguide or horn antenna) to be directed from the top onto the mixture and any molten glass that has already formed. The waveguide should be positioned and oriented in such a way that it cannot penetrate the top layer of the mixture and that a large portion of the microwave radiation is absorbed by the mixture.

All other areas, and at least the lautering section, are heated with plasma and one or more plasma torches. The hot gas and plasma from these torches should be introduced parallel to the melt through appropriately shaped and suitable refractory bricks above the melt. Depending on the size of the system, the plasma torch(s) can be positioned perpendicular to or parallel to the flow direction. The plasma-heated area is at least long and wide enough to allow the hot gases from the plasma torch(s) to spread in a flame-like pattern, thus utilizing the heat content of the gases without damaging the refractory lining. A plasma torch should facilitate a U-shaped flow pattern. This can be achieved by positioning the plasma inlet and exhaust gas outlet in the same wall. Positioning them at the same height or at different heights is possible.

Both the melting area and the refining area are lined with suitable refractory material that is suitable for both the temperatures and the expected chemical attack from the molten glass. The housing or oven can be insulated with suitable thermal insulation material so that the external wall temperatures meet technological, normative and legislative requirements.

The heating system should be dimensioned to continuously melt the desired mass flow of glass mixture. The microwave source(s) should be capable of supplying all the necessary energy. Supplementary heating using conventional electric heaters, e.g., made of SiC, is possible in both the melting and refining stages.

The plasma source(s) should be selected to generate a sufficiently hot gas flow while simultaneously supplying enough energy to the system to compensate for heat losses through the walls and exhaust gas flow. Overall, the combined heating system should be capable of supplying enough energy to the furnace to maintain a continuous melting process.

The glass mixture used as starting material can be introduced via a microwave-tight feed directly next to a microwave source, such as a waveguide, in such a way that a cone of material that is as flat as possible is created, with which a maximum thickness of the mixture can be achieved that is suitable to be completely penetrated by the microwaves in order to achieve the most energy-efficient melting possible.

The molten glass can be removed from the end of the lautering section and any conditioning zone through a bottom outlet. The bottom outlet can be regulated with a plunger for better control of the bath height.

Exhaust gases can be directed into an exhaust system through a suitable outlet.

Temperature monitoring should be provided at least in the lautering area; for safety reasons, further measuring points, e.g., at any additional heating system, in the melting area and in the exhaust gas line, can also be equipped with suitable temperature sensors. The melting zone should allow for lower temperatures at the top of the housing during continuous operation, as the layer of melted glass covers and thermally insulates the already molten glass. For this to happen, the melting process and the feed of melted glass should be continuous and in balance with the outflow into the melting zone. This can be achieved by adjusting the feed rate, the skimmer, and the microwave power.

A skimmer is a barrier made of refractory material, such as AZS, which extends from above into the molten glass. The skimmer can be adjusted so that only molten glass from the melting zone can flow into the refining zone, and so that as little hot gas as possible from the refining zone can enter the melting zone.

The glass mixture is introduced into the inclined bed melter through the inlet area. Beneath the waveguide, the mixture forms a continuous blanket, ensuring that it does not touch the microwave sources, such as the waveguide itself. In the melting zone, the glass mixture is directly melted by the microwave radiation and flows continuously due to the incline of the melter. The microwave source(s) (e.g., a tuner) can be controlled to couple the microwave radiation directly into the mixture. The molten glass then flows through the refining zone, where the plasma torch(s) act. The plasma torch(s) should be oriented so that it does not directly sweep over the molten glass to prevent the formation of hotspots. Furthermore, its flow pattern should be designed to create an egg-shaped flow pattern with the gas jet.

By regulating the plasma torch(s), the average gas temperature of the plasma torch(s) can be adjusted so that it reaches and maintains the target temperature of the lautering section. Finally, the glass is discharged from the inclined bed melter through the bottom outlet. The flow rate can be adjusted by changing the inclination of the inclined bed melter. A plunger can be used to control the outflow and to control the melt bath height in the lautering area.

Additional conventional electric heating can be used to improve heating and holding processes, and can also support the melting process. All heating systems should be coordinated.

The invention can also be used wherever small quantities of glass with high purity requirements need to be melted quickly, for example, to meet changing production demands. Examples include the production of optical glass for lenses or glass production and processing laboratories. Additionally, its use in the production of dental glass ceramics is conceivable.

The invention will be further explained below by way of example.

Figure 1 shows a sectional view of an example of a device according to the invention.

The illustrated example features a housing 6 that should enclose all other parts of the device. It should only have an inlet opening 1.1 for the mixture, a bottom outlet 4 for the finished glass melt, and an exhaust outlet opening (not shown) to the outside.

The inlet opening 1.1 is followed by an inlet section 1, inclined downwards in the horizontal direction, through which the mixture can be fed in solid form. In this example, the angle of inclination relative to the horizontal is 32°. The mixture introduced there can then be melted at the end of the inlet section 1 and in the melting section 5 using the energy of a microwave source 2. The microwaves are emitted towards the mixture for this purpose.

Due to the inclination at a smaller angle than that of the inlet area 1, the molten glass formed can flow into the refining area 7, which is located downstream of the melting area 5. Melting area 5 The lautering area 7 can be easily separated from each other using a skimmer positioned above the glass melt.

The molten glass is then heated with the energy of at least one plasma torch and the plasma itself, both of which are generated by at least one plasma source 3. The plasma is generated with supplied plasma gas. This also means that a plasma torch can extend as far as the lautering stage 7.

At the end of the lautering section 7, the bottom outlet 4 can be located, through which the finished glass melt can be fed to further processing. ```

Claims

Patent claims 1. Device for producing a glass melt, in which a housing (6) is connected to an inlet region (1) inclined at least partially vertically downwards in a horizontal direction, to which a melting region (5) and a refining region (7) are connected, wherein the melting region (5) and the refining region (7) are also inclined downwards in a horizontal direction starting from the inlet region (1), and the melting region (5) and refining region (7) are lined with refractory material, so that the formed glass melt flows by gravity to a bottom outlet (4) for finished molten glass, wherein at least one microwave source (2) is arranged above the melting region (5) to melt the mixture introduced into the inlet region (1), which emits microwaves in the direction of the mixture discharged through the inlet region (1) and the melting region (5), characterized in that at least one plasma source (3) is arranged on the housing (6) and thus is designed so that the glass melt formed in the melting area (5) can be sufficiently purified in the refining area (7) with the plasma and at least one plasma torch formed therewith. 2. Device according to claim 1, characterized in that the inlet area (1) is inclined at an angle which ensures that the introduced mixture reaches the melting area (5) in such a way that the mixture has a maximum thickness with which safe melting of the supplied mixture by means of microwave energy can be achieved. 3. Device according to one of the preceding claims, characterized in that the inlet area (1) is inclined or tiltable at an angle in the range of 30° to 40° with respect to the horizontal. 4. Device according to one of the preceding claims, characterized in that the microwave source(s) (2) and the plasma source(s) (3) are designed and aligned such that the microwave source(s) (2) and the plasma torch(s) do not have direct physical contact with the mixture or the formed glass melt. 5. Device according to one of the preceding claims, characterized in that the melting area (5) and the lautering area (7) are separated from each other by a skimmer in such a way that the penetration of the mixture and of gases into the lautering area (7) from the lautering area (7) into the melting area (5) is prevented. 6. Device according to one of the preceding claims, characterized in that different gases, vapors and/or particles can be introduced into the lautering area (7) by means of the plasma torch. 7. Device according to one of the preceding claims, characterized in that the flow guidance of the gases over the plasma torch and the exhaust gas opening in the lautering area (7) is designed in such a way that a U-shaped flow guidance is achieved. 8. Device according to one of the preceding claims, characterized in that conventional heating elements are provided for heating the melting area (5) and the purifying area (7). 9. Device according to one of the preceding claims, characterized in that different operating temperatures can be set in the melting zone (5) and in the lautering zone (7). ...