Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
  • C03B17/04—Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

• the present invention relates to a method for drawing a quartz glass cylinder from a crucible, which comprises a crucible interior, which extends in the direction of a crucible center axis and is bounded by a side wall and a bottom, by feeding the crucible SiO 2 grain, softened into a viscous quartz glass mass and this deducted by means of a first extraction device through a provided in the bottom of the crucible first die as a cylindrical quartz glass strand vertically downwards and from the quartz glass cylinder is cut to length.
• the invention relates to a device for drawing a Quarzglaszy- Linders, with a crucible for receiving SiO 2 grain, which comprises a crucible interior, which extends in the direction of a crucible center axis and is bounded by a side wall and a bottom, with a heating device for softening the SiO 2 grain, as well as with a first die nozzle provided in the bottom of the crucible, and with a first removal device for drawing off a quartz glass strand through the first die.
• Quartz glass melt a relatively high-viscosity quartz glass mass
• a funnel is usually provided, which protrudes into the crucible, and whose lower end ends above the surface of the viscous quartz glass mass.
• a bulk cone forms from the granular SiO 2 raw material which floats on the surface of the melt.
• the SiO 2 -Körnungsteichen on the direct line connecting the Schüttkegelmitte and the die of the crucible a comparatively lower residence time in the melt and a correspondingly lower temperature exposure.
• This effect is further enhanced by the fact that the axial temperature profile along the crucible center axis by up to 50 0 C lower temperatures than at the edge, which can go so far that SiO 2 grain is not completely melted in the center of the crucible and disturbances in the withdrawn glass strand leads.
• the "silo flow" is unfavorably noticeable especially in the case of small die dimensions and requires an extension of the mean residence times for the SiO 2 grain in total and limits the efficiency of the melt throughput.
• a method of this kind describes the DE 1 596 664 A, from which a device of the type mentioned is known.
• a tungsten nozzle is used, which spans a circular opening into which protrudes from above a mandrel which is held on a hollow shaft of tungsten hanging in the quartz glass melt. The position of the cathedral is changeable.
• the mandrel has an upper part with a bulge in the form of an hourglass, which is connected via an intermediate ring with a frusto-conical lower part which extends into the nozzle opening while leaving an annular gap which can be changed in its width.
• the geometry of the upper part deflects the central, colder melt streams and thus homogenizes the temperature within the quartz glass melt.
• the device used in the known drawing method is relatively complicated in its construction and handling and the method proves to be relatively sensitive to temperature fluctuations in the interior of the crucible.
• the present invention is therefore based on the object of specifying a method which allows the production of homogeneous quartz glass cylinder with high productivity.
• the invention has for its object to provide a structurally simple and easy-to-use device for performing the method.
• this object is achieved on the basis of the above-mentioned method according to the invention in that at least one second quartz glass strand is drawn off by at least one further second die nozzle provided in the bottom of the crucible, the first die and the second die being spaced apart from each other and eccentric to the crucible. Center axis are arranged.
• the aim of the invention is to avoid a pronounced silo flow in the center of the crucible, accompanied by an immediate entry of small homogenized quartz glass mass into the die, and at the same time to increase the productivity of the drawing process.
• the interaction of several measures is crucial for this:
• the at least two drawing nozzles generate individual flows which are partially coupled to one another and which interact with one another. This results in a certain mixing effect, which contributes to a homogenization of the quartz glass mass.
• the same product-specific standard melt performance results in an increase in the residence time in the crucible and, consequently, a higher quality of the withdrawn quartz glass, and vice versa, while maintaining the customary residence times customary hitherto, there is an attributable increase in the melting performance.
• Quartz glass strand improves or - with constant homogeneity - the temperature load of the crucible can be reduced. These measures also indirectly affect productivity, as explained above.
• first die and the further, second die have a distance of at least 20 mm, preferably at least 50 mm from each other.
• the distance is not understood to be the distance of the center axes of adjacent drawing nozzles, but the smallest distance of the respective nozzle openings. The distance thus describes the remaining between the nozzle openings minimum web width in the crucible bottom.
• the eccentric disposition of the dies with respect to the crucible centerline also includes a technique in which one of the die orifices intersects the crucible centerline. In a particularly preferred procedure, however, it is provided that the drawing nozzles are arranged distributed uniformly around the crucible center axis.
• a procedure is preferred in which a quartz glass strand is drawn off with a first mass flow through the first die, and a quartz glass strand is withdrawn through the second die with a second mass flow, wherein the first and second mass flow are maximally 100% (based on the smaller of the mass flows).
• the mass flows are as small as possible. It has proved to be advantageous if the opening cross section of the first and second die is a maximum of 50 cm 2 each.
• the extraction device is provided for simultaneous removal of several quartz glass strands from the drawing dies.
• this requires the same geometry of the die openings and the deducted quartz glass strands.
• the two quartz glass strands can be deducted independently of each other and regulated to their nominal dimensions.
• the first extraction device preferably has a first roller tractor, which extends over a first extension section along the crucible center axis
• the second extraction device has a second roller tractor, which extends over a second extension section along the crucible center axis, such that the extension sections of the first and second roller tugs do not overlap.
• a roller tractor comprises a plurality of tow rollers distributed around the glass strand to be drawn, which are opposite to the glass strand to be drawn off and exert on them a force which is suitable for removing the glass strand.
• the trigger in the form of a roller tractor allows continuous pulling the glass strand with relatively little design effort.
• it is preferred that the roller tractors of the first and second extraction device are arranged on different height levels.
• the above-mentioned object starting from a pulling device of the type mentioned is achieved in that in the bottom of the crucible at least one further, second die is provided, and that first die and second die spaced from each other and arranged eccentrically to the crucible center axis are.
• the aim of the invention with respect to the device is to avoid a pronounced silo flow in the center of the crucible by means of simple constructional means, and at the same time to increase the productivity of the drawing process.
• the interaction of several measures is crucial for this:
• the at least two drawing nozzles generate individual flows, which are partially coupled with each other and act on each other. This results in a certain mixing effect, which contributes to a homogenization of the quartz glass mass and thus also to a reduction of Matehalausschuss.
• the same product-specific standard melt performance results in an increase in the residence time in the crucible and, consequently, a higher quality of the withdrawn quartz glass, and vice versa, while maintaining the customary residence times customary hitherto, there is an attributable increase in the melting performance.
• Figure 1 shows an embodiment of a melting furnace according to the invention with a crucible with a plurality of dies in a side view and as a sectional view, and
• FIG. 2 is a plan view of the underside of the bottom of the crucible of FIG. 1.
• the drawing furnace according to FIG. 1 comprises a crucible 1 made of tungsten into which SiO 2 grains 3 are continuously introduced from above via a feed neck 2 .
• the crucible 1 is surrounded by a water-cooled furnace shell 14 to form a protective gas space 10 purged with protective gas, within which a porous insulation layer 8 of oxidic insulation material and a resistance heater 13 for heating the SiO 2 grain 3 are deposited. were brought.
• the inert gas chamber 10 is open at the bottom and otherwise sealed with a bottom plate 15 and a cover plate 16 to the outside.
• the crucible 1 encloses a cylindrical crucible interior 5 with an inner diameter of 400 mm, whose cylinder longitudinal axis is coaxial with the crucible center axis 6.
• the crucible interior 5 is also sealed from the environment by means of a cover 18 and a sealing element 19.
• Through the cover 18 protrude an inlet 22 and an outlet 21 for a crucible interior gas in the form of pure hydrogen.
• the inert gas chamber 10 is provided in the upper region with a gas inlet 23 for pure hydrogen.
• drawing nozzles 4a and 4b are used eccentrically to the central axis 6, each with a circular opening, which also consist of tungsten components 17.
• the drawing nozzles 4a, 4b are identical in construction and taper from top to bottom first to a minimum inside diameter of 40 mm before they expand again to 70 mm in the region of the lower nozzle opening.
• the soft quartz glass mass 9 exits via the drawing dies 4a, 4b and is drawn off vertically in the direction of the crucible center axis 6 in the form of two solid cylinder strands 11a, 11b, each with a diameter of 70 mm, by means of roller towers 12a, 12b.
• the roller tractors 12a, 12b are arranged offset from one another via the height and in each case connected to a control and regulating device (not shown in the figure) for regulating the diameter of the respective solid cylinder section 11a, 11b. Pieces of the desired length are cut to length from the two full-cylinder strands.
• the quartz glass mass 9 is exposed in the near-edge region of the crucible 1 on average higher temperature than in the central region, it is better homogenized in the two near-edge main mass flows than would be the case for a given crucible temperature in the central region. Silo flow through the central crucible region comprising the crucible centerline 6 is thus completely avoided and the productivity of the draw process is doubled.
• the SiO 2 grain 3 is heated in the crucible 1 to a temperature of about 2050 0 C to 2150 0 C, ie about 50 0 C less than in Example 1.
• the quartz glass mass 9 in the main mass flows 20a, 20b is exposed to approximately a temperature load, such as the "silo flow" in a conventional drawing process, and the solid cylinder strands 11a thus obtained, 11 b thus have approximately the same homogeneity as the central strand produced in the conventional drawing process.
• a temperature load such as the "silo flow" in a conventional drawing process
• the solid cylinder strands 11a thus obtained, 11 b thus have approximately the same homogeneity as the central strand produced in the conventional drawing process.
• the temperature load of the crucible wall 1 and the crucible bottom 7 is lower, there is less input of abrasion from the crucible and other impurities into the softened quartz glass mass and a longer service life of the crucible. The scrap is thus lower and the maintenance interval greater, resulting in higher productivity.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Glass Melting And Manufacturing (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2009
  • 2009-06-26 DE DE102009030852A patent/DE102009030852B3/de not_active Expired - Fee Related
• 2010
  • 2010-06-15 WO PCT/EP2010/058359 patent/WO2010149530A1/de active Application Filing
  • 2010-06-15 US US13/381,050 patent/US20120174629A1/en not_active Abandoned
  • 2010-06-15 CN CN201080029079.0A patent/CN102471118B/zh active Active
  • 2010-06-15 EP EP10724515A patent/EP2445843A1/de not_active Withdrawn
  • 2010-06-15 JP JP2012516637A patent/JP5538533B2/ja not_active Expired - Fee Related

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