Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/027—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by passing an electric current between electrodes immersed in the glass bath, i.e. by direct resistance heating
  • C03B5/03—Tank furnaces
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/02—Details
  • H05B3/03—Electrodes
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/08—Bushings, e.g. construction, bushing reinforcement means; Spinnerettes; Nozzles; Nozzle plates
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/027—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by passing an electric current between electrodes immersed in the glass bath, i.e. by direct resistance heating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/027—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by passing an electric current between electrodes immersed in the glass bath, i.e. by direct resistance heating
  • C03B5/03—Tank furnaces
  • C03B5/031—Cold top tank furnaces
• • 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 electric glass melting techniques in which the conductivity of molten glass is used to develop by Joule effect the energy necessary for the melting of raw materials.
• the energy is supplied by means of electrodes totally immersed in the mass of molten glass (hereinafter called the bath), arranged vertically on the bottom of the oven and / or horizontally on the side walls of the oven, the composition to be melted being introduced from above so as to maintain a surface layer constituting both a permanent reserve of raw materials and a protection of the bath against surface heat losses.
• the molten glass bath is the seat of convection movements, due to changes in the density of the glass according to its degree of heating, which participate in the transport of heat to the surface layer where the fusion must take place as well as in the rest of the volume of the bath. These movements are particularly intense along the electrode due to the temperature gradient existing with the neighboring mass of glass.
• ovens of this type comprise a tank made of very deep refractory material, usually of the order of at least 1.5 m, in which a thickness of molten glass of the order of at least 1.2 at 1, 4 m is provided so that the materials which melt under the surface layer have a sufficient residence time in the bath to reach a state of uniform composition and temperature, and thus develop a satisfactory glass.
• the technique of electric fusion has undergone an important modification, consisting in immersing the electrodes in the bath through the free surface of the latter, instead of causing them to spurt out inside the bath from the sole. .
• This made it possible to resolve the delicate problems of replacing worn electrodes and of sealing linked to the passage of the electrodes through the refractory of the sole.
• the wear of the refractories could also be reduced because the use of plunging electrodes eliminates direct heating at the level of the bottom, the hot zones being located in an upper part of the molten bath, and therefore makes it possible to limit the development of currents. convection in contact with the bottom.
• This configuration also made it possible to increase the possibilities of adjusting the production parameters.
• the design of the ovens has not been significantly modified with the use of plunging electrodes, and a minimum depth has hitherto been recommended to properly develop the temperature gradient necessary for establishing the temperature at the bottom.
• relatively low desired the temperature profile in the bath is indeed such that the temperature is higher near the electrode and decreases relatively slowly towards the floor. This minimum depth was also considered necessary for the production of good quality glass.
• the object of the invention is to improve the definition of electric melting furnaces with plunging electrodes, so as to optimize the production conditions in particular by reducing, for equal production, the investment and / or operating cost, for improved profitability. .
• the subject of the invention is an oven for the preparation of glass by electric melting in which the melting energy is dissipated by the Joule effect in the molten mass, comprising means for supplying vitrifiable materials depositing said materials in layer on the surface of a molten glass bath and submerged melting electrodes immersed from the surface of the bath through the layer of melting composition covering the molten bath, characterized in that the height h of the molten bath is less than 800 mm and the ratio of the height h to the surface S of the bath is less than 0.5 m / m 2 .
• the height h of the molten bath actually designates the useful height of the molten bath, namely the height between the upper level of liquid in the tank and the bottom of the oven, or possibly in certain cases where the racking glass is made at a higher level than that of the sole, between the upper level of the liquid in the tank and the lower level of the glass withdrawal orifice.
• the useful height of the molten bath namely the height between the upper level of liquid in the tank and the bottom of the oven, or possibly in certain cases where the racking glass is made at a higher level than that of the sole, between the upper level of the liquid in the tank and the lower level of the glass withdrawal orifice.
• the oven according to the invention has a characteristic aspect ratio with a bath height limited to a value less than 800 mm and low compared to the surface of the bath.
• the height h of molten glass can advantageously be reduced to a value less than 500 mm, in particular less than or equal to 450 mm, with a very significant reduction in the cost of the furnace. Heights less than or equal to 400 mm, in particular of the order of 300 mm or less, are particularly preferred.
• the h / S ratio defined above is moreover less than or equal to 0.05, for example of the order of 0.03 or less. According to preferred variants where the oven has a large surface area for a high production capacity, the h / S ratio can even be less than or equal to
• the height of the tank will advantageously be limited accordingly, preferably to a value greater than the height of the bath from 100 to 200 mm, in particular of the order of 150 mm.
• the invention therefore has the remarkable feature that it makes it possible to process the same quantity of materials as a traditional oven with the same specific draft, but in an oven of reduced height: in fact, if the electrodes provide the same quantity of energy, they transmit it to a lower bath volume.
• the temperature profile in the bath is such that it is established in the mass of molten glass of the glass circulation currents conducive to the development of a homogeneous glass.
• the furnace is characterized by a bath height of less than 800 mm, in particular less than 500 mm, in particular less than 450 mm, and by an exchange surface between the electrodes and the molten glass (this surface being constituted by the lateral electrode surface immersed under the upper level of liquid present in the tank, per unit of bath volume) greater than 0.075 m 2 of electrode per m 3 of glass.
• the mass of glass has a higher energy exchange surface than usual. There is therefore a quantity greater relative glass exposure to electrodes than in traditional ovens.
• the electrode surface per unit volume of bath is advantageously greater than 0.1 m 2 per m 3 , preferably greater than or equal to 0.15 m 2 per m 3 , in particular of the order of 0.2 m 2 per m 3 or more.
• the depth of immersion of the electrodes in the molten bath is necessarily limited to a value less than the height of the bath to avoid contact between the electrode and the bottom. This immersion depth must however be sufficient to provide the exchange surface necessary to dissipate the desired power.
• the immersed length of the electrodes is less than or equal to two thirds of the height of the bath, preferably at half the height of the bath, the depth of immersion also depends on the height of the bath. This makes it possible to locate the hottest areas in the vicinity of the surface of the bath, the fusion energy being dissipated where it is most needed. This precaution also proves to be favorable for a circulation of the molten materials along a path allowing the rapid production and homogenization of the glass within the shallow bath.
• the shape of the electrodes can be adapted so that they have a very high lateral surface for a minimum of length.
• Electrodes in particular of substantially cylindrical outline, whose dimensions are such that their lateral surface S e , and their submerged length I are in a ratio S é , / I greater than or equal to 0.45, advantageously 0, will therefore be advantageously used. , 6.
• At least one electrode can comprise at least one substantially planar conducting element.
• such an electrode may have the form of a plate or comprise several plates associated with one another.
• a substantially planar conducting element may nevertheless also have the form of a ribbon or be composed of a plurality of juxtaposed wires.
• such plates are square or rectangular, in particular for reasons of ease of manufacture, although any other shape of plate also makes it possible to supply the glass bath with electric current for the creation of a Joule effect.
• the cylindrical type electrodes are in fact less preferred according to the invention as soon as the depth of the glass bath becomes increasingly shallow since, to obtain a sufficient lateral exchange surface with a short submerged length, it is necessary to use a large diameter cylinder, therefore relatively heavy.
• One solution may consist in using a hollow cylinder, since only the lateral surface of the electrode participates in the electrical exchange, the internal part being completely inert in this respect.
• This solution is however of no economic interest in the current state of the technology of materials capable of constituting the electrodes (such as molybdenum) because a hollow cylinder can only be manufactured by milling, the material eliminated, lost, entering all the same cost of manufacturing such a hollow electrode.
• the dimensions of the plates are chosen as a function of the desired exchange surface, the thickness being chosen to ensure that the electrode has sufficient longevity as a function of the wear kinetics by consumption of the conductive material constituting the electrode under the conditions the oven.
• the electrode comprises at least one plate, in particular rectangular, arranged in such a way that its larger side is oriented in a substantially horizontal direction.
• the support element is connected to the larger dimension side of the plate or plates.
• the thickness of the plate can be chosen to ensure a resistant fixing when the support element enters the plate in particular by screwing. It is possible to combine conductive plates in a wide variety of configurations:
• - three square or rectangular plates can be arranged in a U; - four square or rectangular plates can be arranged to form a hollow parallelepipedal electrode.
• the associated plates for example as above are assembled together, in particular by screwing or any other means.
• Electrodes of different configurations can be used in combination in the same oven to provide a particular distribution of current lines. It is thus possible to install, in an oven for example, both cylindrical electrodes and plate-shaped electrodes, or else both L-shaped and U-shaped electrodes.
• the electrodes made up of plate (s) can also be provided with means for adjusting the orientation of the electrical exchange surfaces, in particular by pivoting around at least one axis, in particular a horizontal axis and / or a vertical axis, so as to adjust the distribution of the current lines in the molten glass bath.
• an essential feature of the melting technique according to the invention is the short average residence time of the molten materials in the oven in the bath, relative to the rate of production which is generally expressed by the specific draw T spec which is the quantity of glass (in tonnes) drawn from the oven per day compared to an oven surface of 1 m 2 .
• T spec which is the quantity of glass (in tonnes) drawn from the oven per day compared to an oven surface of 1 m 2 .
• the subject of the invention is also a process for the electrical melting of glass in which the energy is dissipated by the Joule effect in the molten mass from plunging electrodes, comprising the steps consisting in distributing the materials constituting the composition to melt in a layer on the surface of the bath, immerse the electrodes from the surface of the bath through said layer of composition to be melted, supply the electrodes with an electric current, the materials melting and combining in the bath to form the glass and withdraw the molten glass with a flow rate expressed by the specific draw T spec
• the average residence time of the materials in the bath between the surface layer and the withdrawal zone is less than or equal to 0.7 days, advantageously 0.5 days, for example of the order of 0.25 to 0.4 days, for a specific pulling of the order of 3 t / m 2 / d.
• the oven according to the invention proves to be particularly advantageous for the production of “opaque” glasses with infrared radiation, such as for example glasses containing a relatively high proportion of iron oxide (for example of the order of at least 0 , 60% Fe 2 O 3 , up to 10 - 12% or more) in which the radiation develops in a limited way.
• the low conductivity of the radiation creates marked temperature differences between the zones of the bath, with in particular relatively cold zones at the bottom of the bath where the glass tends to devitrify. Because of its shallow depth, the oven according to the invention allows the establishment of a thermal gradient avoiding the creation of these cold zones and limiting the risks of devitrification of these particular glasses.
• the melting technique according to the invention makes it possible to produce, with less expensive apparatus and under more economical operating conditions, good quality glass usable for very numerous applications with results as satisfactory as glass produced in traditional ovens.
• the molten glass according to the invention can be transformed into glass wool, in particular for the production of insulating products, of quality equivalent to existing wools.
• the invention also relates to an installation for manufacturing glass wool comprising a glass melting furnace, a fiberizing device and means for supplying the fiberizing device with glass. melt produced in said furnace, characterized in that the furnace is a furnace with plunging electrodes of shallow depth as described above.
• FIG. 1 shows schematically an installation for manufacturing glass wool using an electric oven according to the invention
• FIG. 2 shows a schematic view in longitudinal section along the axis ll-ll of the oven of Figure 1;
• - Figure 3 shows a schematic view in longitudinal section along the axis III-III of the oven of Figure 1;
• FIG. 4 shows a side view in partial section of a plate-shaped electrode usable in an oven according to the invention
• FIG. 6 shows a side view in partial section of an electrode consisting of an assembly of plates usable in an oven according to the invention
• FIG. 7 shows an elevational view of the plate assembly shown in Figure 6.
• the installation shown in Figure 1 is intended to produce glass wool for the production of thermal insulation materials. It essentially comprises a glass melting furnace 1 supplied with a mixture of vitrifiable materials by a supply system 2, a channel 3 for transporting the molten glass produced in the furnace 1 and a fiberizing machine 4 supplied with molten glass by the channel 3.
• the molten glass falls into a fiberizing plate 5, the side wall of which is pierced with a multitude of orifices, rotated around a vertical axis 6, so as to eject centrifugally the glass melted through said orifices in the form of glass filaments 7 solidifying by cooling.
• the constitution of the furnace 1 appears in detail in the two sectional views of FIGS. 2 and 3.
• the furnace comprises a tank 8 made of refractory material constituted by a hearth 9 and vertical walls 10, and surmounted by a vault 11.
• the tank shown has a horizontal sole 9.
• the tank 8 of the oven according to the invention can take any traditional general shape, but is distinguished from traditional ovens by the low height of the walls 10.
• the tank shown has an area of approximately 10 m 2 for a 0.4 m high.
• the tank 8 contains a mass of molten glass 12 constituting the melt, covered with a layer 13 of solid raw materials distributed continuously by the supply system 2.
• This layer as uniform as possible may be more or less thick depending on the operating regime.
• a thickness of at least 100 mm is preferably maintained to thermally isolate the molten bath from the atmosphere.
• this thickness should not exceed approximately 300 mm since this does not provide any advantage for the melting and would therefore unnecessarily overload the surface of the bath.
• the height h of the bath is calculated by measuring the difference between the level of free glass in the transport channel 3 and the level of the floor 9. In the mode shown, it is approximately 300 mm; the h / S ratio is therefore 0.03 (in m / m 2 ).
• the molten material is discharged through a groove 14 located on one side of the tank 8 and at the same level as the floor 9, this groove communicating with the channel 3.
• Fusion electrodes 15, six in number in this example, are arranged in the upper part of the oven, carried by supports 16 of the traditional type. Their arrangement, of the type described in EP-A-0 140 745, is more particularly suitable for a three-phase current supply, the distribution of the phases (R, S, T) being as indicated in FIG. 3. This arrangement allows good phase balancing. Any other usual feeding method can however be envisaged in the context of the invention.
• the electrodes 15 pass through the surface layer of raw materials and enter the molten bath.
• the lowest possible immersion depth is preferred, provided that the necessary exchange surface is provided.
• an immersion depth less than 2/3 the height of the bath and even preferably half this height will generally be advantageous.
• the electrodes are cylindrical in shape, short but of relatively large diameter to provide a large exchange surface.
• the lateral exchange surface S é is approximately 0.095 m 2 per electrode and the ratio S é , / I is 0.63.
• the electrodes are immersed over their entire useful length 150 mm, that is to say half the height of the bath, the exchange surface per unit volume of bath therefore being 0.190 m 2 per m 3 of bath.
• this oven can be supplied with a current density on the electrode of the order of 1 to 3 A / cm 2 .
• the furnace supplied with a current density of 2 to 2.5 A / cm 2 makes it possible to produce glass with a specific draw on the order of 3 t / d / m 2 , i.e. total drawdown of 30 t / d: with a glass whose density is 2.4 t / m 3 , the volume of glass produced is 12.5 m 3 per day. Knowing that the volume of the bath is 3 m 3 , the residence time of the materials in the bath is about 0.25 day with a floor temperature in the usual range.
• FIGS. 4 and 5 represent an electrode 19 in the form of a plate usable in the furnace 1 in place of at least one of the cylindrical electrodes 15.
• the actual electrode consists of a rectangular molybdenum plate 20 connected to a steel extension 21 by screwing.
• the plate 20 is provided with a thread 22 formed in the thickness of the plate in the middle of the side of greatest dimension (length).
• the extension 22 is provided with a corresponding threaded end 23.
• the extension 21 is the connection means between the electrode and the support arm of the assembly: its function is to support the electrode and to bring the electric current to the electrode. In operation, it passes through the layer 13 of raw materials surmounting the bath, the lower portion with the thread 23 inserted in the plate 20 being approximately at a level corresponding to half the thickness of the surface layer 13.
• a cooling system 24 of the "water-jacket" type integrated in the extension 21 To avoid melting of the fixing between the electrode and the steel extension, and to avoid wear of the molybdenum in the fixing zone in the upper part of the plate 20, a cooling system 24 of the "water-jacket" type integrated in the extension 21.
• This system comprises a circuit 25 for circulating cooling water inside the extension between an inlet orifice 26 and an outlet orifice 27.
• the extension 21 provided with the cooling system 24 is equipped with a plate 28 for connection to a support element (arm) not shown penetrating through the side walls of the oven.
• a plate electrode 19 functionally equivalent to the cylindrical electrode 15 described above has a length of 300 mm, a height of 150 mm and a thickness of 45 mm.
• the diameter of the tapping 22 should preferably be as large as possible in order to have the strongest possible attachment of the electrode. This furthermore results in better cooling of the entire supported electrode area since the threaded end 23 of the extension 21 enclosing the end of the cooling system 24 provides a higher water flow rate.
• the shoulder 29 on the extension 21 is such that it projects beyond the thickness of the plate 20.
• this front contact surface it is on this front contact surface that the electrical contact supplying the electrode. It is therefore advantageous for this contact surface to be as large as possible in order to avoid excessive current densities on this connection surface of the electrode.
• the weight of the plate 20 is only about 21 kg instead of
• the plate electrode 19 is more than twice as heavy as the cylindrical electrode 15.
• This electrode 19 was tested under the same operating conditions as those described above with the electrode 15 with a current density at the electrode of approximately 2 A / cm 2 .
• the fusion has the same qualities with the two types of electrodes. While the cylindrical electrode 15 wears with a loss of 3.1 grams of molybdenum per tonne of glass produced, the electrode 19 wears with a loss of 2.9 grams of molybdenum per tonne of glass produced. Thanks to the cooling of the threaded end of the extension 21, the wear of the plate takes place from the external rectangular faces without prejudice to the electrical contact. The thickness of 45 mm of the plate 20 is sufficient to ensure satisfactory longevity of the electrode. This could be explained in particular by the fact that, with equal loss of mass, the surface of a plate would decrease less quickly than the surface of a cylinder.
• Figures 6 and 7 show a hollow electrode 30 with square section, consisting of the assembly of four plates 31, 32, 33, 34 of molybdenum fixed to a support plate 35 of molybdenum by screws 36 also of molybdenum.
• the support plate 35 is provided with a thread 37 making it possible to fix the electrode on an extension not shown, which may be of structure similar to the extension 21 provided with a cooling system.
• the square electrode 30 allows the diffusion of electric current in four perpendicular directions instead of two opposite directions.
• the dimensions of the plates 31, 32, 33 and 34 are such that each face of the electrode measures 160 mm wide by 150 mm high, which gives a total lateral exchange surface of 0.096 m 2 , that is to say of the order of that of electrode 15.
• the electrode 30 is also twice as efficient as the cylindrical electrode 15.
• the electrodes 19 and 30 can be provided with means for adjusting their orientation, in particular by pivoting about a vertical axis or a horizontal axis, to adjust the distribution of the current lines in the molten bath.
• the electrode 19 includes such means of orientation around a vertical axis, in the form of the union fitting 40 between the extension 21 and the support 28.
• the glass produced in the oven 1, once led to the fiberizing machine 4, is transformed into glass wool with a proportion of fiber-like materials as low as with the glasses obtained from traditional ovens.
• the step of transporting the molten glass to the processing device can advantageously be used to homogenize and refine the glass.
• the routing conditions were not optimal or if the glass produced in oven 1 was not sufficiently homogeneous or refined due to uncontrolled variations in production parameters, it was observed that the fiber product nevertheless exhibits satisfactory qualities.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Glass Melting And Manufacturing (AREA)
• Furnace Details (AREA)
• Resistance Heating (AREA)
• Surface Treatment Of Glass Fibres Or Filaments (AREA)

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• 1998
  • 1998-07-21 EP EP98939727A patent/EP0944555A1/de not_active Withdrawn
  • 1998-07-21 CZ CZ991010A patent/CZ101099A3/cs unknown
  • 1998-07-21 CN CN98801038A patent/CN1234784A/zh active Pending
  • 1998-07-21 BR BR9806062-7A patent/BR9806062A/pt not_active Application Discontinuation
  • 1998-07-21 CA CA002266648A patent/CA2266648A1/fr not_active Abandoned
  • 1998-07-21 JP JP11509415A patent/JP2001501167A/ja active Pending
  • 1998-07-21 PL PL98332381A patent/PL332381A1/xx unknown
  • 1998-07-21 AU AU88139/98A patent/AU746124C/en not_active Expired
  • 1998-07-21 WO PCT/FR1998/001597 patent/WO1999005068A1/fr active IP Right Grant
  • 1998-07-21 KR KR1019997002403A patent/KR20000068601A/ko not_active Application Discontinuation
  • 1998-07-21 TR TR1999/00631T patent/TR199900631T1/xx unknown
  • 1998-07-21 US US09/147,854 patent/US6125658A/en not_active Expired - Fee Related
  • 1998-07-22 AR ARP980103583A patent/AR016528A1/es not_active Application Discontinuation
• 1999
  • 1999-03-10 IS IS4994A patent/IS4994A/is unknown
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