DE10202024B4 - Apparatus and method for low-contamination melting of a substance - Google Patents

Abstract

Device (1, 101, 201, 301) for melting a substance, in particular for melting high-purity, aggressive and / or high-melting glass or glass-ceramic, comprising
a melting pot (10),
a transmitting device (30) for electromagnetic radiation, wherein energy can be coupled into a melt (40) which can be arranged in the melting crucible (10) by means of the radiation, and
a mixing device or homogenizing device (50, 150, 250, 350, 350 '), wherein the mixing device or homogenizing device (50, 150, 250, 350, 350') is associated with the melting crucible (10), wherein the mixing device or homogenizing device comprises a device for Introducing gas or gas bubbles (52) into the melt (40) with one or more gas nozzles (50), characterized by means (58) for piercing one of the crucible walls (12, 14) over an outlet opening (56) of the gas nozzle (n) (50) fixed skull layer (42, 42a).

Description

The The invention relates to an apparatus and a method for low-contamination Melting of a substance in general and for melting in particular high purity, aggressive and / or high melting glass or glass ceramic particularly.

In traditional fusion, glass is continuously in one Platinum crucible or melted in refractory tubs. adversely Here is that given by the platinum shares in the melt and the refractory tubs have only short lives. The desired high-purity glass quality can not be achieved here become.

It Methods are also known in which glass in melting tanks continuously is melted and removed. This close to high quality To obtain glass, optionally a Läuterrinne and a homogenizer or trough to the melting tank.

at both methods mentioned, discontinuous or continuous, are the crucible or the melting tank, z. B. with a Burner from the outside heated and the heat is conductively passed on to the melt located inside. There is a direct contact between the melt and the crucible or the tub. This has a number of disadvantages on.

First is the maximum melt temperature through the crucible or tub material limited. Usually Therefore, consist of the crucible or the trough and optionally the lauter trough and the homogenization tray made of platinum, which is a relatively high Melting temperature and relatively good corrosion resistance having.

Further is the platinum crucible or the platinum melting tank, but also the Läuterrinne and the Homogenisierungswanne attacked by the molten glass and corroded.

Indeed causes platinum disadvantageously contaminations or impurities in the glass, which has the optical properties, in particular the Transmission deteriorate, which is why these conductive heating methods for high purity Glasses at most limited are applicable. Such impurities lead to transmission losses in optical fiber transmission systems of up to 200 to 500 dB / km.

This proves especially for the melting of aggressive glasses, z. As zinc silicate or Lanthanboratgläser as highly problematic, since these literally "eat" the crucibles or pans.

Next The above-mentioned conductive heating methods are still Such methods are known in which glass in a so-called Skulltiegel inductively heated and melted.

One Skull crucible typically consists of spaced, meandering arranged water-cooled Metal pipes. The melt inside the scull crucible will over a arranged around the Skulltiegel coil assembly by means of coupling heated by high frequency power in the melt.

By the cooling The skull crucible is created between the skull crucible and the melt a substantially solid layer or crust of inherent material, d. H. in particular of glass. In this respect, impurities are the Melt significantly reduced by the crucible material.

A skull crucible is z. From PETROV YU. Et al., Continuous Casting Glass Melting in a Cold Crucible Induction Furnace, XV. International Congress on Glass 1989, Proceedings,
Vol. 3a, 1989, pages 72 to 77.

In the DE 199 39 780 A1 a Skulltiegel for the melting or refining of glasses and glass ceramics is described, in which the crucible wall is formed from a ring of metal pipes, which are connectable to a cooling medium. The tubes of the ring are short-circuited with a short-circuit ring. By choosing the position of the short-circuit ring, the temperature distribution of the melt in the crucible can be influenced.

The DE 199 39 785 A1 describes a method and apparatus for making colored glasses. The convection currents forming in a skull crucible due to the large temperature gradients are used to rapidly disperse the dye for the glass in the melt.

Furthermore, in the DE 101 38 109 A1 a method and an apparatus for producing optical glasses described. In order to extract water from the molten glass, it is proposed to introduce chlorine gas or a chlorine-oxygen mixture into the melt with a cooled platinum tube.

However, due to the complex structure, in particular due to the high-frequency technical requirements of an inductively heated Skull-melting device compared to said conductive heating melting devices completely new requirements and problems. Therefore, first, a transfer is due to high Melting temperature and very high throughput per pot volume of many solutions of conductive heating devices on skull melting devices not readily possible.

Basically with a skull melting device high melting rates and thus throughputs realizable. While this is desirable, but on the other hand, this may possibly the quality of the melt and thus the final product, eg. B. suffer from thermal reduction. This too leads to deteriorated transmission properties of the glass.

Further depends on that Coupling rate of high-frequency radiation of various parameters the melt from. Thus, the melting performance is not only by the high-frequency power emitted by the coil arrangement, but also limited by the melt parameters and crucible geometries.

From the DE 199 39 780 A1 is a Skulltiegel for the melting or refining of glasses or glass ceramics known, which is provided with a short-circuit ring. By means of the short-circuit ring, the high-frequency field z. B. pressed into the bottom area, wherein a convection of the melt is generated.

Furthermore, from the DE 199 39 785 A1 a method and an apparatus for producing colored glasses known. Here, the melt is fed in the course of further processing in a scarfing device, in which the melt is subjected to convection. This Skulleinrichtung is located behind a smelting station.

The However, known skull melting devices are particularly in terms of the quality and homogeneity the melt as well as in terms of Melting power or throughput can be further improved.

From the WO 00/32525 For example, there is known a method and apparatus for glazing organic waste, in particular radioactive waste, in which the supply of oxygen serving for the oxidation of the organic substances is carried out both from the surface and from the underside of a crucible. The supply of oxygen is essentially such that it has locally limited influence. As a result, however, the redox state of the melt is changed only locally and does not occur a homogenization of the entire melt.

Therefore It is an object of the present invention to provide a device and a method, in particular a skull melting device or a skull fusion method for melting a substance, in particular glass or glass ceramic available which has improved homogeneity, increased melting performance, one increased Throughput and / or a high substance or glass quality allow.

A Another object of the present invention is known skull melting devices or Skull Fusion continue to develop and the disadvantages of known devices and Avoid or at least mitigate procedures.

The The object of the invention is surprising simple way already by the subject of claims 1 and 20 solved.

The device according to the invention, in particular skull melting device for melting or melting a substance or compound, in particular for melting of high-purity, aggressive and / or high-melting Glass or glass ceramic comprises a, preferably coolable, z. B. water-cooled crucible or Skulltiegel and a transmitting device for electromagnetic radiation, in particular a coil arrangement arranged around the crucible. The transmitting device or coil arrangement emits, in particular high-frequency electromagnetic Radiation, which is in a melt, which is in the crucible, is coupled, so that the melt absorbed by the High frequency power is heated. Further, a mixing or homogenizing device intended for mixing or homogenizing the melt, wherein the Mixing or homogenizing associated with the crucible, z. B. on and / or are arranged in this, so that the mixing or Homogenizing can take place in the crucible or crucible.

Prefers is continuously melted mixture from above approximately in the middle placed on the melt and continuously liquid melt from the crucible taken.

The inventors have found that by mixing and / or homogenizing the melt already in the crucible or skull crucible a surprising multiple benefits can be achieved. First, unmelted mixture, which z. B. falls from above in solid form in the melt, melted faster by increased mixing with the liquid portion of the melt. Surprisingly, the inventors have found that the effective contact area between the melt and the supplied Good greatly increased and thus the melting performance is increased. Second, the temperature distribution of the melt is leveled. Third, a uniform distribution or mixing of different glass components, which z. B. different melting temperatures and / or Hochfrequenzankopplungs coefficients, achieved. Fourth, the redox state of the glass can be adjusted.

The found mechanisms of action are particularly in connection with the preferably used inductive high-frequency heating relevant because the coupling or coupling of the electromagnetic radiation also of the physical state, the temperature and the respective glass component in dependent on the melt are. In particular, the coupling to unmelted batch constituents is very low.

The inventive device and the method are particularly suitable for high-melting glasses, in which melt temperatures of at least 1500 ° C or 1600 ° C driven become. Furthermore, can also excellent aggressive glasses, z. As zinc silicate or Lanthanboratgläser be melted.

The Mixing or homogenization is preferably carried out without contamination or at least low in contamination, which is especially high purity Glasses of great Advantage is.

Preferably is the melt for mixing or homogenizing targeted or in predetermined way into internal movement or it will be a Encouraged, supported and / or sustained internal movement. In particular, a predefined flow, e.g. B. with predefined flow rate and / or flow direction in the melt excited. It can, for. B. by targeted generation of a Temperature difference in the melt causes a convection flow, or an existing convection flow stimulated, supported or reinforced become.

The Mixing or homogenizing can be done with or without incorporation of material be induced or generated in the melt.

A preferred form of material-introducing mixing comprises introduction of mixtures, which is designed so that alone by introducing z. B. a flow in the melt is excited becomes. For this purpose, z. B. a pelleted and / or sugar-coated Mixture in which in particular gas bubbles are enclosed and / or which releases gas bubbles during melting used. Without these Gas bubbles may also be pelleted, sugar coated and / or otherwise mixed supplied compacted become. For the purposes of the invention is in this case as pelleting the Bringing together a stable solid, for example by means of Pressing understood. As a dragging one with one, for example glassy coating solid-like Structure understood. This is in a particularly advantageous manner both a dusting by feeding granular and fine granular Materials avoided and above addition, the fill rate significantly improved because at the same volume flow a clear increased Material entry can take place in the melt. Furthermore, batch components by fine-grained Substituted material without causing increased dustiness comes, passing it through the fine-grained material by means of shortened Diffusion paths to an optimized melting speed comes.

alternative or in addition is preferably a z. B. shaped rods to bars, which in particular by rotating into the melt, mixing or homogenizing causes hung up. The z. B. propeller-shaped rods define in particular a self-dissolving one Stirrer.

alternative or in addition can also be an external stirring device, in particular of coated metal for mechanical stirring or a immersed in the melt and, for. B. by melting self-dissolving stirrer be provided the melt material.

According to the invention is also a device for introducing gas or gas bubbles by means of a or more gas nozzles provided in the melt. The gas nozzle is preferably cooled, in particular liquid cooled, z. B. water cooled and is preferably located at the bottom of the crucible. The cooling of the gas nozzle can with the cooling of the crucible connected or formed separately.

According to one particularly preferred embodiment sticks out the gas nozzle at least in sections through the bottom of the crucible and extends into the interior of the crucible. In particular, extends a tip of the gas nozzle up to or into the melt, leaving the gas nozzle or Tip escaping gas in the form of gas bubbles rises in the melt. This "bubbling" causes in a particularly simple manner mixing and homogenizing the melt in the crucible.

O ₂ -containing gas is preferably used, which proves to be very advantageous, in particular, for lead silicate glasses. In fact, in these, the lead is thermally reduced at high melt temperature, which is used for a high Aufschmelzleistung. This, in turn, causes transmission degradation of the glass similar to platinum contamination which can lead to severe discoloration affecting the molten glass completely unusable. By introducing oxygen into the melt, the lead is prevented from being reduced so that effective control of the redox state of the glass is achieved via the introduction of gas. This can even z. B. for lead silicate glass melting performance of about 500 kg / day, 800 kg / day, 1000 kg / day or more can be achieved and at the same time a significant transmission deterioration avoided or at least mitigated.

Preferably, the portion of the nozzle which projects into the melt, so z. B. the tip of low-contamination material, eg. B. a light metal, in particular aluminum, magnesium or beryllium or is coated at least with such a material. A coating with polytetrafluoroethylene ( ^Teflon® ) also appears possible.

Around after a "freezing" of the gas nozzle, d. H. after formation of a solid substance or glass layer over the gas nozzle, to open these or to make them free again, the gas nozzle includes a Device for puncturing a solid substance or skull layer. This device is to pierce especially as a needle, z. B. of high temperature resistant material, like tungsten or similar Metal, made. Preferably, the needle is in the center of the gas nozzle, preferably longitudinal displacement arranged.

in the The invention is based on preferred embodiments and with reference to the figures, wherein like reference numerals same or similar Designate elements.

Brief description of the figures

It demonstrate:

1 a schematic sectional view of a first embodiment of the device according to the invention with a gas nozzle,

2 a schematic plan view from above of a section of the crucible bottom according to the first embodiment of the invention,

3 a schematic sectional view of a section of the crucible bottom along the section line AA in 2 .

4 a schematic sectional view of an upper portion of the gas nozzle according to the first embodiment of the invention,

5 a longitudinal section of the gas nozzle according to the first embodiment of the invention,

6 a cross section of the gas nozzle along the section line BB in 5 .

7 a schematic sectional view of a second embodiment of the invention,

8th a schematic sectional view of a third embodiment of the invention,

9 a schematic sectional view of a fourth embodiment of the invention and

10 a schematic perspective view of a self-resolving stirrer according to a fifth embodiment of the invention and

11 a schematic sectional view of the first embodiment of the invention with a Läuterrinne and a Homogenisierungswanne.

Detailed description of the invention

1 shows a first embodiment of the device according to the invention 1 for melting glass with a cooled, z. As water-cooled crucible or crucible 10 , To the crucible 10 is a transmitting device for electromagnetic radiation in the form of a coil arrangement 30 arranged. By means of the coil arrangement, high-frequency power is converted into a melt 40 z. B. from lead silicate glass and thus the melt 40 heated. It is operated at a high frequency of about 250 kHz to about 400 kHz with a transmission power of about 200 kW to about 300 kW or higher. The temperature of the melt is in the range of 1200 ° C to 2000 ° C.

The crucible 10 includes a water-cooled annular wall section 12 and a water-cooled floor 14 , The wall section 12 and the ground 14 together form the chilled wall of the crucible 10 and each comprise meandering and spaced metal tubes 16 how best in the 2 and 3 you can see. The metal pipes 16 have a cross section of about 2 cm and 5 mm gaps between the tubes 16 on, so that the crucible wall with unfilled crucible 10 initially liquid permeable.

By cooling the wall section 12 and the soil 14 , So the crucible wall is formed in the contact area of the melt 40 and the crucible wall a tight closed skull layer 42 made of material of inherent material, ie in this embodiment of glass, whereby the arrangement of the crucible 10 and the solid skull layer 42 becomes liquid-tight. 1 shows a schematic representation of the crucible, the individual tubes 16 and the skull layer 42 Not.

Further referring to 1 it is noted that the melter is operated continuously so that blends through a generally central orifice regularly occur 20 in a cover 18 of the crucible 10 is placed on the melt. Furthermore, there is continuous melt over an outlet opening 22 of the crucible 10 taken.

A cooled bridge 24 dives near the outlet 22 at least about 3 cm to 5 cm deep in the melt 40 one to unmelted or undissolved batch ingredients from the outlet port 22 keep.

The device 1 further includes two burners 26 . 28 passing through openings in the cover 18 Flames 27 . 29 on the crucible contents or a surface 41 the melt 40 judge. This serves the burner 26 for initial melting of the crucible contents when starting the device 1 , z. B. after a crucible change and the burner 28 for continuous reheating of the melt 40 in the outlet opening 22 ,

On the ground 14 of the crucible 10 is a mixing or homogenizing device in the form of a gas nozzle 50 arranged. The gas nozzle 50 projects sectionwise into the crucible, and passes the gas into the melt 40 one.

Further, the gas nozzle 50 eccentric, in this embodiment approximately centrally between the center and the edge of the round crucible 10 and opposite the outlet opening 22 arranged. This position has proved to be very advantageous, since a temperature difference in the melt anyway present centrally of a hot core 43 ascending and descending convective flow 54 supported and at the same time centrally through the opening 20 Applied mixture by means of gas bubbles 52 from the cold crucible wall 12 kept away. The substantially annular flow 54 advantageously causes effective mixing and homogenization of the melt and thus ensures a temperature balance and a uniform distribution of material in the melt.

In this example, the gas bubbles contain O ₂ to simultaneously lead in the lead silicate glass melt 40 to oxidize.

2 shows a schematic view from above on the bottom of the crucible 14 with the gas nozzle 50 which is in an opening 15 or recess in the crucible bottom 14 between the meandering metal pipes 16 is arranged.

As in further 3 is shown, the Skullschicht forms 42 not only on the cooled floor 14 of the crucible, but also on the cooled gas nozzle 50 out. The escaping gas bubbles 52 However, ensure that an opening of the gas nozzle is kept permanently.

Nevertheless, it can, for. B. by an interruption of the gas supply come to the fact that the solid Skullschicht 42 above an outlet opening 56 the gas nozzle 50 closes, leaving no gas from the nozzle 50 can escape. This condition is in 4 shown. Around the opening 56 To free up again, the gas nozzle comprises a needle 58 pointing in the direction of the arrow 59 longitudinally displaceable within a channel 60 is arranged in the center of the gas nozzle. With a tip 62 the needle 58 thus one can over the gas outlet opening 56 lying section 42a the skull layer 42 pierced, and so the gas outlet opening 56 be released again.

The inventors have found that an upper section 51 the gas nozzle 50 which is in the crucible 10 protrudes and at least partially in direct contact with the skull layer 42 is preferably made of nichtkontaminierendem or at least low contamination material. For the purposes of the invention, such materials are considered to be low in contamination and do not affect the glass quality substantially or only slightly. These are in particular light metals, such as. As aluminum. Although aluminum enters the melt, aluminum ions or aluminum compounds have essentially no or little negative effect on the optical properties, in particular the transmission of the glass. The cooling of the gas nozzle 50 on the other hand ensures that the gas nozzle 50 the high temperatures in the crucible 10 withstand.

Furthermore, the use of a high melting point metal, e.g. B. higher than 2000 ° C, in particular molybdenum, iridium, tungsten or a tungsten compound as advantageous for the needle 58 proved.

5 shows the gas nozzle 50 in a longitudinal section. The gas nozzle 50 includes the gas outlet opening 56 and the gas channel 60 in which the needle 58 runs and is guided. By means of a displacement device 64 can the needle 58 parallel to the channel 60 inside the gas nozzle 50 be moved. The gas nozzle 50 further includes a gas inlet 66 and a seal 68 for the needle 58 , The upper section 51 the gas nozzle 50 includes aluminum or an aluminum-containing alloy, with a lower section 53 the gas nozzle 50 made of brass. The upper and lower sections 51 . 53 are through seals 70 fluid-tight sealed against each other. In the lower section 53 there is a cooling water inlet 72 and a cooling water outlet 74 , so that the gas nozzle by means of water flow can be effectively cooled.

Referring to 6 showing a cross section of the nozzle, it is shown that the lower section 53 parallel to a longitudinal axis L of the gas nozzle 50 in two halves 53a . 53b , which are electrically isolated from each other, divides.

7 shows a second embodiment of the device according to the invention 101 with an alternative device 150 for mixing and homogenizing the melt 40 , About a conveyor belt 154 becomes pellets, dragées and / or balls 156 shaped glass batch through the opening 20 in the melt 40 brought in. The glass balls 156 include an outer edge area 158 and an inner core area 160 , The border area 158 essentially comprises glass of the composition of the melt 40 , The core area 160 comprises a substance which in the melt is a gas or gas bubbles 152 releases when the edge area 158 is melted. The substance in the core area 160 may be a gas, a liquid, eg. As water or a solid material, for. B. include a salt, which in cooperation with the hot melt 40 the gas bubbles 152 release.

By lowering the glass balls 156 in a left section 40a the melt and an increase of the gas bubbles 152 in a right section 40b the melt 40 becomes a substantially annular flow within the melt 40 generated or induced. But it can also, as in 1 is shown, an already existing convection flow are supported.

8th shows a third embodiment of the device according to the invention 201 in which by means of a mixing and homogenizing device 250 rod-shaped pressed mixture body 256 in the melt 40 be introduced. The rod-shaped body 256 are z. B. of propeller-like shape and rotate when descending within the melt 40 with simultaneous melting of the body 256 and thereby generate flow processes in the melt 40 ,

9 shows a fourth embodiment of the device according to the invention 301 with a stirrer 350 which is the melt 40 in the melting pot 10 mechanically rotated by rotating motion.

10 shows a preferred embodiment of an elongated agitator 350 ' , The stirrer 350 ' is essentially made of glass, for. B. pressed, which is also the melt 40 forms. The stirrer 350 ' becomes along its longitudinal axis 352 z. B. similar to the stirrer 350 in 9 from above into the melt 40 introduced and around its axis 352 turned. The stirrer 350 ' comprises three stirring arms extending away from the center and dissolves itself by melting in the melt 40 on. To ensure continuous glass addition and stirring, the stirrer becomes 350 ' accordingly continuously tracked from above.

11 shows the first embodiment of the device according to the invention 1 with an attached lauter trough 80 and an additional external homogenizer 90 , It is continuously liquid glass from the crucible 10 along the arrow 82 into the lauter trough 80 and from there along the arrow 84 further into the external homogenizer 90 guided. The external homogenizer 90 includes a glass outlet 92 for casting, z. B. in a form and / or for further or finishing of the glass to a glass product or glass ceramic product.

By refining the glass in the lautering channel 80 and post-homogenizing in the external homogenizer 90 the quality of the glass is further improved. However, the glass quality achieved with the device according to the invention can already be so high that the Läuterrinne 80 and / or the homogenizing device are not necessary, so that the molten glass 40 already at the outlet opening 22 is available for further or final processing.

It It will be apparent to those skilled in the art that the invention is not limited to the above described embodiments limited is and in more diverse Way can be varied without departing from the spirit of the invention.

Claims (18)

Contraption ( 1 . 101 . 201 . 301 ) for melting a substance, in particular for melting high-purity, aggressive and / or high-melting glass or glass ceramic, comprising a melting crucible ( 10 ), a transmitting device ( 30 ) for electromagnetic radiation, whereby by means of the radiation energy in a, in the melting pot ( 10 ) can be arranged melt ( 40 ) and a mixing device or homogenizing device ( 50 . 150 . 250 . 350 . 350 ' ), wherein the mixing device or homogenizing device ( 50 . 150 . 250 . 350 . 350 ' ) the melting pot ( 10 ), wherein the mixing device or homogenizing device comprises a device for introducing gas or gas bubbles ( 52 ) in the melt ( 40 ) with one or more gas nozzles ( 50 ), characterized by a device ( 58 ) for piercing one on the crucible wall ( 12 . 14 ) above an outlet opening ( 56 ) of the gas nozzle (s) ( 50 ) fixed skull layer ( 42 . 42a ). Contraption ( 1 . 101 . 201 . 301 ) according to claim 1, characterized in that the crucible ( 10 ) an outflow opening ( 22 ) for the melt ( 40 ) and a, in particular cooled bridge ( 24 ), which in the melt ( 40 ), wherein by means of the bridge ( 24 ) unmelted batch portions from the outflow opening ( 22 ) are kept away. Contraption ( 301 ) according to one of the two preceding claims, characterized in that the device comprises a stirring device ( 350 . 350 ' ), which the melting pot ( 10 ) assigned. Contraption ( 301 ) according to one of the preceding claims, characterized in that a stirrer ( 350 ' ), which in the melt ( 40 ) dissolvable or meltable. Contraption ( 1 ) according to one of the preceding claims, characterized in that the gas nozzle (s) ( 50 ) is cooled, in particular liquid-cooled (are). Contraption ( 1 ) according to one of the preceding claims, characterized in that the gas nozzle ( 50 ) on the ground ( 14 ) of the melting pot ( 10 ) is arranged. Contraption ( 1 ) according to one of the preceding claims, characterized in that at least a first section ( 51 ) of the gas nozzle ( 50 ) into the interior of the melting pot ( 10 ) and / or the first section ( 51 ) Contaminationsarmes material, in particular light metal, z. B. aluminum includes. Contraption ( 1 ) according to one of the preceding claims, characterized in that the needle ( 58 ) in the center of the gas nozzle ( 50 ) is arranged. Method for melting a substance, in particular for melting highly pure, aggressive and / or high-melting glass or glass ceramic, in particular for operating the device ( 1 . 101 . 201 . 301 ) according to one of the preceding claims, the method comprising providing a melting crucible ( 10 ), Providing a transmitting device ( 30 ) for electromagnetic radiation, in particular cooling of the melting crucible ( 10 ), Heating a melt contained in the crucible by means of electromagnetic radiation, which from the transmitting device ( 30 ) and mixing or homogenizing the melt ( 40 ), characterized in that the mixing or homogenization of the melt ( 40 ) in the crucible ( 10 ) and for mixing or homogenizing via one or more gas nozzles ( 50 ) a gas or gas bubbles ( 52 ) are introduced into the melt, with one at the crucible ( 12 . 14 ) over an outlet opening 56 the gas nozzle (s) ( 50 ) is a solid skull layer ( 42 . 42a ) by means of a device ( 58 ) is pierced. A method according to claim 9, characterized in that for mixing or homogenizing the melt ( 40 ) is purposefully put into internal movement. Method according to one of the preceding method claims, characterized in that for mixing or homogenizing a flow in the melt ( 40 ) is excited in a predetermined manner. Method according to one of the preceding method claims, characterized in that for mixing or homogenizing a first material ( 52 . 156 . 256 ) is introduced into the melt, wherein the first material ( 52 . 156 . 256 ) a substantially predefined flow movement in the melt ( 40 ) or at least stimulates. Method according to one of the preceding method claims, characterized in that a crucible ( 10 ) with an outflow opening ( 22 ) for the melt ( 40 ) and a, in particular cooled bridge ( 24 ), which in the melt ( 40 ) is provided, whereby by means of the bridge ( 24 ) unmelted batch portions from the outflow opening ( 22 ) are kept away. Method according to one of the preceding method claims, characterized in that a mixture ( 156 . 256 ) in the melt ( 40 ), the composition of the mixture ( 156 . 256 ) or the form of batch ingredients are designed such that the introduction of the batch ( 156 . 256 ) in the melt ( 40 ) mixing or homogenizing the melt ( 40 ) causes. Method according to one of the preceding method claims, characterized in that a pelleted and / or sugar-coated mixture ( 156 . 256 ) in the melt ( 40 ) is introduced. Method according to one of the preceding method claims, characterized in that a mixture ( 156 ) in the melt ( 40 ) is introduced, which on melting a gas or gas bubbles ( 152 ) releases. Method according to one of the preceding method claims, characterized that the melt ( 40 ) is stirred for mixing or homogenizing. Method according to one of the preceding method claims, characterized in that a self-dissolving stirrer ( 350 ' ) in the melt ( 40 ) is introduced.