DE2056445A1 - Process and equipment manufacturing of glass - Google Patents

Description

65o2

Patent attorneys

Dr.-Ing. Wilhelm Reicliel Dipl-Ing. Wolfgang Reichel

6 Frankfurt a. M. 1 Parking street 13

The General Electric Company Limited London, England

Method and apparatus for making glass

The invention relates to the manufacture of glass by Electric Schipelzen, and more particularly relates to an improved method of stirring the molten glass during the casting process or the refining and the construction of a glass melting furnace to carry out the process according to the invention. The term “glass” is also to be understood below as vitreous silica.

109822/1305

In the method for the production of glass according to the present invention, which includes the melting of the glass-forming constituents by heating, since the passage of electric current is effected, during at least part of the casting and refining process the molten glass is subjected to a magnetic field which is oriented in this way is that it generates a magnetic J ¹ IuU (this also includes linear field components) which is directed essentially at right angles to the direction of flow of the heating current flowing through the glass, the magnitude of the heating current being such that the Y / The interaction of the current with the force generated by the magnetic field is sufficient to affect the stirring of the molten glass.

Normally the glass is heated by the passage of an alternating current, in this case the magnetic field must also be designed so that it oscillates at the same frequency as the heating current when the oscillations of the magnetic field do not necessarily have to be in phase with those of the current.

It is already known that some stirring of the molten glass in a furnace can be achieved by convection currents W which come from a non-uniform

'The glass warms up. Furthermore, it is already known to encourage the stirring of the glass by means of glass bubbles which are passed through the melt. However, both of these known "experienced in stirring" are difficult to control, while the method according to the present invention has the advantage that the stirring achieved thereby is completely controllable. The degree of stirring to be achieved can therefore be controlled by a suitable setting of the strength of the applied magnetic field while the location is controlled in the melt in the stirring should werdfn effected by changing the position of the magnetic polo

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can be, or by using several magnets verv / ends werat-n. Further, the electromagnetic agitation generated can counteract excessive undesirable agitation exercise by convection.

The effect of the electromagnetic forces on the flow lines of a fluid is primarily determined by the magnitude of these forces relative to the convection forces that act simultaneously on the fluid, that is, the buoyancy forces that arise from the thermally generated light gradients. "The ratio of the electromagnetic Forces to the convection forces, related to a small volume element of the fluid, where the electric current and the magnetic Ji ¹ IuB are perpendicular to each other and lie in a horizontal plane, can be expressed in any unified system of units by the following formula:

N ₂ = J3 _

" P g / 3 &

Where J is the current density, 3 is the positive magnetic density, P is the fluid density, g is the acceleration due to gravity, / 3 is the expansion coefficient of the fluid volume and 0 is the temperature difference between the element of the fluid and its surroundings. To achieve an optimal stirring effect, which is generated by the interaction of the electric current with the magnetic field, the value of N _{E is} preferably at least 1, although a useful degree of stirring with values of Ng less than 1 can be achieved. The value of N i is considered here under the initial conditions, and as the electromagnetic stirring progresses, the temperature difference decreases, so that the value of N i increases. The dynamic

Behavior of the molten glass under the influence of electromagnetic and convection forces becomes natural.

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through the balance of these forces and viscosity of the glass determined.

The force generated by the interaction of the heating current and the applied magnetic field is according to the known electromagnetic induction laws into a

iz to the current exerted a direction which is both * and perpendicular to the field. It has been found that when an alternating heating current with a frequency of 50 Hz and a magnetic field at right angles to it, which oscillates at the same frequency, is applied, with magnitudes of the current and the magnetic field such that the root mean square value of the vector product yields a Tesla current of 2.2 amps, the resulting force can assist the movement of a liquid which has an electrical resistance similar to that of the molten glass, which is sufficient to cause a damming head of 30 mm in size. For example, at a flux density of 2oo Gauss,

2, which is perpendicular to a current density of 0.03 cm, in a body made of molten glass one meter in the direction of the magnetic flux, a movement of the glass on a circular path in the right y-angle both to the magnetic flux and to the current at a medium speed of at least 4 cm / seo. can be achieved.

In order to be able to apply a magnetic field to the molten glass according to the method according to the invention, at least one magnet is suitably arranged in or on the glass melting furnace. The core of the electromagnet, which can consist of normal, ferromagnetic material such as laminated iron and / or of a suitable Perritzueammensetzung, is attached to the outside of a glass melting tank or another form of a GIaβ furnace chamber, the magnetic core being designed so that it adapts to the geometry of the furnace chamber ". The poles of the magnet are in relation to the

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Melting furnace chamber located electrodes, zv / ischen which the heating current flows through the glass, arranged so that the magnetic flux generated within the glass when the electromagnet is excited is essentially perpendicular to the flow of the nucleus flow through the glass. Of the The cross-section of the magnetic core is advantageously Y / eise at least i / 7o of the inner cross-section of the glass furnace chamber in the plane which forms right angles to the direction of the generated llagnetflusses.

Palis it is necessary can while the molten glass one or during all of the various stages of the casting process and the refining are subjected to the action of a magnetic field, the magnetic core or the Cores around the appropriate part or part of the furnace are arranged.

If necessary, multiple electromagnets, which can be energized separately, can be used to generate desired magnetic streamlines in a furnace chamber. For example, in the case of a furnace chamber having an elongated shape, some electromagnets may be placed at intervals along the length of the arms and operated so as to produce a nearly uniform agitation of the whole portion of the molten glass within the chamber, or so that they produce a Generate the desired variety of different glass streamlines one after the other. The construction and the arrangement of the magnet or magnets can alternatively or additionally be such that the position of the Aiagnetpole can be changed in order to achieve a variety of glass streamlines. The glass current lines can also be changed by changing the phase relationship between the electric current and the magnetic field,. and by the direction of the by the magnet or the . Magnets generated Lagnetstrom is reversed. The switching

-6-

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circuit arrangement for actuating the electrodes and the or the liagneten can be programmed to run on a continuous basis To achieve a switching cycle and to generate a circular run of the glass streamlines, the circular frequency can be so be designed to be uniform or changeable if necessary.

An arrangement in which one or more electromagnets are used to carry out the method according to the invention can be designed so that it can be actuated by either a single-phase or a polyphase alternating current source. In both cases, a conventional. Circuitry as well as used to actuate the magnet or magnets' for powering the electrodes in the Schmelzofenkarnmer. -

For a more detailed explanation of the invention, some special designs of glass melting furnace are shown with reference to the drawing indicated, with which the method according to the invention can be carried out. Here show:

Fig. 1 in a partial cross-sectional side view of the pre-chamber a glass melting furnace, which is provided with two solenoids and which are designed so that they can be operated from a single-phase Wschselstromqutlle,

Pig. _t 2 shows a section along the line II-II. Pig. 1, ,

Pig. 3 a circuit used to operate the in the Pig. 1 and 2 is the embodiment shown,

Pig. 4, 5, 6 and 7 streamlines in the melted gins,

the one with the one in Pig. 1 and 2 ·· ^x Torrn under different operating conditions

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be told

Pig. 8 is a partial sectional view of a rectangular one Gas melting tank furnace with. a single electromagnet, which can be operated from a single-phase AC source,

Pig. 9 shows a section along the line IX-IX according to FIG. 8,

Fig. 1o is a partial sectional view of a hexagonal glass melting tank furnace with electrodes and an electromagnet that can be operated from a three-phase source and

11 is a perspective view of an alternative embodiment for three-phase operation in FIG a hexagonal tank.

In Figs. 1 and 2, the refractory walls of the antechamber are denoted by 1, in which three electrodes 2, 3 and 4 are shown, and which are equipped with two electromagnets, of which the cores 5 and 6 around the lower part of the chamber are arranged, and the pole parts 7, 8, 7a (not shown) and 8a are partially embedded in the side walls of the comb 1; The exciter coils 9 and 1o 'd'er magnets are wound around the central legs of the corresponding cores. If necessary, means not shown here can be used for water cooling of the pole part of the ... magnets.

The circuit of Fig. 3 shows in which way the elec trodes 2, 3 and 4 and the magnetic excitation coils 9 and 1o bit of a single-phase AC power source 11 are connected. The coils 9 and 1o are arranged so that they are sueinsnder and 'to the central electrode 3 in series and the Ua-

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pole switches 12 and 13 are provided to change the direction of the Current flow through the coils 9 and 1o, depending on how it is necessary to change accordingly. The Y / i resistances 14 and 15 represent the molten glass in which the electrodes are immersed and through which the heating current flows.

The direction of the flow of electric current during the operation going into the pig. 1, 2 and 3 is indicated for a half-wave by the arrows in l ⁽¹ ig. 3 and by the arrows with broken lines 16 in FIG broken lines 17 in Fig. 2. It can be seen that the current ^u 9 is horizontal in each case and that they are directed perpendicular to one another, both reversing during the alternating half-waves Glass is exercised is directed vertically and downwardly, as indicated by arrow 18 in Fig. 2, whereby a vertically directed stirring of the glass results.

FIG. A ₁ 5, 6 and 7 show power lines that are 3 due to the interaction dee electric current with the magnetic flux in the different operations stages generated in the molten glass in the embodiment according to Fig. 1, and wherein the effect of the Convection currents have been omitted for the sake of simplicity. Each of these figures shows the same view of the antechamber of FIG. 1, the position of the electrodes being indicated by 2, 3 and 4 and that of the positional poles by 7 and 6, and the streamlines of the glass are in each case indicated by the lines Arrows indicated within chamber 1. The flow dea electrical current through the molten

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Glass runs for each pail as shown in Fig. 1, the formation of the Stromi'lussee between the electrodes 2 and 3 in. Each half-wave is the reverse of that between electrodes 3 and 4.

Pig. 4 shows the state that exists when the heating current flows through the glass alone, ie when there is no magnetic flux; In this space the glass flows straight through the antechamber without stirring taking place (except for that which is generated by convection and which, as already explained above, is not taken into account). Pig. 5 shows the streamlines that arise due to the interaction of the heating current with the magnetic flux generated by the excitation of the two electromagnets, the plus between the poles of the corresponding magnets, as indicated by the plus and minus signs, in run in the opposite direction and .this operating state is achieved if the circuit is as in Pig. 3 is shown switched. The relative direction of the magnetic flux generated by the two magnets and the phase relationship between the electric current and the magnetic field can be determined by a corresponding actuation of the reversing switches 12 and 13, which are located in the circuit according to Pig. 3 are to be changed. The Pig. 6 shows the flow lines that are generated in the molten glaA when the magnetic flux eraeugt by the two magnets having the same direction and Yig. 7 shows the streamlines that are generated when the magnetic flux of the two magnets is reversed in the same sense as that according to Pig. Runs 6, wherein the magnetic field is phase-shifted with respect to the current elektrieohen to 18o °.

The execution form of the in the Pig. 8 and 9 shown invention has a rectangular GIa aeohmeletank 19 with

¹ ·

Electrodes 2o and 21, by the corresponding

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End walls are inserted so that an alternating current flows through the glass that is in the tank can flow. An electromagnet that is designed to operate from a single phase AC power source is arranged vertically around the outside of the heat-resistant Y / end of the tank, namely transversely to the longitudinal direction of the tank. The magnetic core 22 terminates in two pole pieces 2 $ and 24 of aene one on each side of the tank and partially embedded in the tank wall, and a third pole 251 which is located under the bottom of the tank, namely midway between the two outer poles 23 and 24 and two excitation coils 26 and 27 are around the legs of the core wound between the central pole and each outer pole.

"Liese arrangement of the electromagnet which is actuated in connection with the passage of the ^ eizstromes through the glass, a horizontal agitation generated the glass. The current flow between the electrodes is shown for a ^{£ i} albwelle by the broken lines 28 in Fig. 8 , while the lines of magnetic flux in Fig. 9 are designated 29, and the resulting force on the glass and the streamlines generated are shown respectively by arrow 3o and circles and ellipses 31 in each Fig. For operation with a Single-phase source, the two windings 26 and 27 are connected to one another, and are linked in the circuit in such a way that the generated magnetic field and the heating current are in phase.

Wtnn tin tiniiger electromagnet, which in relation to Fig. and 9 is used, it is horraalerweiat around the central area of the Olaaechmelztanks, like shown arranged. However, the magnet is fixed movably in advance, so that it is close to the tank Wunaoh can be moved in both directions, around the circumference of the molten GIasee in different areas dta tanka au steer.

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The one in Pig. 1o illustrated electromagnet assembly is designed for operation with a three-phase AC power source, and is suitable for use with a glass melting furnace with a regular polygonal or circular cross-section, which is provided with an electrode system for operating from a three-phase source so that a heating current can flow through the glass can.- The particular embodiment shown in the drawing has a regular hexagonal shape of the glass melting chamber 32, which is provided with three electrodes 33, 34 and 35, which are inserted through the three different walls of the hexagon so that they are equidistant from one another . The electromagnet has a horizontal circular core 36 with three poles 37, 38, and 39 which extend through and are partially embedded in the three walls of the hexagonal tank, alternating with those walls which support the electrodes, and three excitation coils 40, 41 and 42 wound around the three legs of the core between the poles. For operation, each solenoid is connected to a different phase of the source and the adjacent electrode for phase synchronization between the electric current and the magnetic field. This arrangement produces a vertical stirring process in the glass, whereby the relative directions of the streamlines can be changed by reversing the polarity of the connections of one or more coils , so that the direction dta current flows through the coil and therefore the inward direction dta generated magnetic fluxes in each Half-wave is reversed *

If ea is required, the arrangement shown in FIG. 10 can be doubled by placing a second electromagnet of the type described above the first together with a wide Sntg electrodes, and by placing the arrangement doubled by 60 ° on a vertical axis the hexagonal GIaaschmelztank is rotated · This doubled arrangement results in a three-dimensional three-haired tray star and creates a thorough stirring of the · glass in the

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The alternative arrangement for a three-phase operation of a bexagomile Gloaschrnelztnnks, which is shown in 1- ¹ I ^. 11, is designed so that it creates horizontal flow lines in the gel. The hexagonal tank 43 is provided with three electrodes 44, 45 and 46 which are passed through the alternating ends of the hexagon. The electromagnet core has three vertical legs 47, 48 and 49, which run parallel to the tank walls, which alternate with those carrying the electrodes, with upper horizontally extending legs ending in poles 50, 51 and 52, which are partly in eten Tiinkwhnen are embedded, and are arranged above the level of the electrodes, and lower horizontally extending legs, which reach below the tank and together end in a fourth pole 53, which is arranged in the middle of the tank bottom. Each of the vertically extending legs of the magnetic core carries an excitation coil 54, 55 and 56, which is respectively connected to a phase of the source and to the electrode, which is passed through the opposite wound of the tank as shown. Similar to the Pail of the arrangement shown in Fig. 10, the stirring process generated in the glass can be changed during operation by reversing the polarity of the connections of one or more coils.

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Claims (1)

Claims Process for the production of glass by melting the glass-forming constituents with the aid of heating, which is effected by the passage of an electric current, characterized in that at least during part of the casting and refining process, the molten glass is exposed to a magnetic field which is directed such that a magnetic flux is generated in the glass which is substantially perpendicular to the direction "'dee through the glass flowing heating current is directed, and its size in relation to the heating current is such that that by the interaction of the current with the magnetic field The force generated is sufficient to affect the stirring of the molten gas. 2. The method according to claim!, Characterized in that ζ e ^ i ο h η e. t that the heating of the glass is effected by the passage of an alternating current, and that the magnetic field is so designed that ee oscillates at the same frequency as the heating current. 3 «The method according to claim 1 or 2, characterized in eic h. η e t, that the magnitude of the magnetic field is such that the ratio of the electromagnetic forces to the contraction forces in the glass is at least 1 . . Glass melting furnace for the production of glass according to the method according to claim 1, 2 or 3, characterized in that the melting furnace (1) has at least one Electromagnet (5,6.), The core of which is arranged in the outer dtr Glaeechmelzofenkamraer (1), and its. Poles (7,7a, 8,8a) in relation to the electrodes (2,3,4), between which the heating current flows through the glass. ■ • V. 109822/1306 V-- C '■' BATH ^{1 ORlGiNAL} forms lind that the inside of the glass when the Electromagnet (5,6) generated magnetic flux runs almost at right angles to the direction of the heating current flowing through the glass. Glass melting furnace according to claim 4, characterized in that the cross section of the magnetic core (5, 6) at least i / 7o of the inner cross-section of the glass melting furnace chamber (1) in the plane which corresponds to the direction of the A: magnetic flux generated by energizing the electromagnet is at right angles. 6. Glass melting furnace according to claim 4 or 5, which is supplied by a single-phase AC power source, and the one Has glass melting chamber with a rectangular cross-section, and has at least three electrodes, which through the Walls of the chamber are used in such a way that they are immersed in the molten glass during operation of the furnace and a heating current through the glass between the electrodes. flows, characterized in that the Furnace has at least two electromagnets (5,6) which alternate with the electrodes (2,3,4) along the chamber (1) are arranged and each electromagnet has a core which is transverse to the exterior of the chamber walls * Length of the chamber is arranged with two poles (7,7a; 8.8a) partly in opposite side walls of the Chamber (1) in the middle between the two electrodes (2,3 baw., 3,4) are embedded and an excitation coil ■ · (1 ο) around the Core is wound in the middle between the poles, and the coils are designed so that they are to each other and can be connected in series to the electrodes for operating the melting furnace. -3- 109822/1305 Glass melting furnace according to claim 4 or 5, which can be operated from a single phase AC power source, which has a glass melting chamber with a rectangular cross-section, and two electrodes through the respective end walls the chamber are inserted in such a way that they are immersed in the molten glass during operation of the furnace and a heating current flows through the glass between the electrodes, characterized in that the furnace (19) comprises an electromagnet (22) having a core which extends around the exterior of the chamber walls transverse to the length the chamber is arranged in the middle between the electrodes (2o) with two poles (23 »24) partially opposite one another Walls of the chamber are embedded, and a third pole (25) is located under the chamber floor in the pipe between the two outer poles (23,24) and two excitation coils (26,27) around the corresponding legs of the core are wound between each outer and the central * pole, wherein the coils are arranged for the operation of the furnace so that they are linked to each other, and in the Power supply circuits so connected to the electrodes can be that the magnetic field ereeugte when the electromagnet is excited is in phase with the heating current. 8. A glass melting furnace according to claim 7 _t characterized in that the electromagnet is movably mounted so that it can be moved along the chamber in both directions. 9 · Glass melting furnace still claim 4 or 5 »which is operated by a three-phase alternating current source and which has a glass melting chamber with a hexagonal cross-section, characterized in that the furnace has three electrodes (53 * 34,35) which are correspondingly alternately passed through three walls of the Hexagons are led, * o that 109822/1305 * - ORIGINAL away they are equidistant from each other, immerse in the molten gloss when the furnace is in operation and the heating current between the electrodes (33,34,35) is designed so that it can flow through the glass, so that an electromagnet creates a horizontally circular core (36) which is arranged around the exterior of the walls of the hexagonal chamber, with three poles (37,38,39) from the core up to. extend to the three wounds of the hexagonal chamber and are partially embedded in it, which alternate with those wounds through which the electrodes are passed, so that three excitation coils (40, 41, 42) are wound around the three legs of the core between the poles, and that for operating the furnace the three coils are arranged so that they can be connected to the corresponding three phases of the source and that each coil is arranged so that it can be connected in series with the adjacent electrode. ίο. A furnace according to claim 4 or 5, which is supplied from a three-phase alternating current source and which has a glass melting chamber with a hexagonal cross-section, characterized in that the furnace has three electrodes (44, 45, 46), which are provided by three corresponding alternating walls of the hexagon, in such a way that β ie 'are equidistant from one another, and that they dip into the molten glass during operation of the furnace, the heating current flowing between the electrodes being adapted so that it can flow through the glass, so that an electromagnet has a core having three vertical legs (47,48,49) which are arranged outside and parallel to the walls of the chamber, which alternate with those walls through which the electrodes (44,45,46) are inserted, and that integral with each vertically extending limb, an upper horizontal limb ends in a pole (5o, 51,52) which is partially embedded in the wall of sorrow, and above depending on the height of the electrodes ** " 1098 22/1305 "bad original 2Ö56A45 (44,45,46) is arranged, and a lower horizontal Leg extends under the chamber and. together with the two other lower horizontal legs in one fourth pole (53) ends, which is arranged in the vitte of the chamber floor, and that the electromagnet 3 excitation coils (54,55,56), corresponding to. the three vertical legs of the core are wound, and that for operation of the furnace the three coils are arranged in such a way that they are correspondingly connected to the three phases of the source and that each coil is arranged to be connected in series with the electrode can, which through the wall of the chamber opposite that of the vertical core leg, which carries the coil, is adjacent, is used. 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