Classifications

• • 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

Definitions

• the invention relates to electric fusion techniques and relates more particularly to those in which energy is dissipated by the Joule effect in the molten mass from plunging electrodes.
• glass production facilities operating on large quantities were provided with melting furnaces supplied with fossil fuel, such as fuel oil or gas. This was in particular the case for large capacity continuous production plants supplying, for example, flat glass or glass.
• electrical energy when it was used, was mainly used as a local backup to maintain the temperature of the glass in the coolest areas, or outside the oven on its way to the place of transformation or to develop certain convection movements to promote homogenization, refining or transport of the molten material.
• the electrodes are arranged vertically in the bath from the bottom of the oven. In other embodiments, there are also electrodes passing through the side walls of the furnace.
• the immersion of the electrodes also allows a convenient and very uniform supply of the surface of the bath with a composition of raw materials.
• the constitution of a relatively thick layer of composition to be melted, floating on the molten bath, is useful indeed for several reasons. It forms, in contact with the molten bath, the permanent reserve of material necessary for continuous operation. It also protects the molten bath from high heat loss by convection in contact with the atmosphere and especially by radiation.
• ovens of the type described in the aforementioned document find very important industrial applications, they do not necessarily make it possible to best meet all the requirements encountered in practice.
• Such a transformation is not possible when it comes to implanting electrodes in the hearth or in the side walls of the furnace.
• Ovens with submerged electrodes offer limited possibilities for electrode adjustment. If they lead to completely satisfactory performance for a certain regime, they are less suitable for frequent and / or substantial modifications of this operating regime.
• the plunging electrode technique locates the hottest areas at the top of the molten bath and thus alleviates these problems.
• this technique makes it possible to modify the immersion depth of the electrodes and therefore the temperature gradient. This allows changes in the oven temperature without changing the temperature of the hearth and, consequently, the temperature of the glass leaving the oven.
• a usual solution consists in raising the immersing electrodes during a standby phase and in maintaining a sufficient temperature in the bath by submerged electrodes most often placed on the walls.
• This technique is effective but we find the problems associated with immersed electrodes although in the present case, they operate at lower voltages since they only maintain the temperature of the already molten bath.
• submerged electrodes require additional investment costs.
• Such a device most often consists of a wire mesh which prevents employees from accessing the oven.
• certain measures which require the presence of an operator near the bath and therefore of electrode supports put this operator in danger.
• the object of the invention is to provide a device for the electrical melting of a vitrifiable charge which acts either under normal operating conditions or during standby without the intervention of submerged electrodes and without risk for operators.
• a fusion electrode support immersed from the surface of a molten bath, said support comprising a current supply system and having thermal protection on the surface, said surface being isolated from the voltage of the current conductor.
• the current supply system is a cooling system, of the "water-jacket" type conducting electric current.
• This device is then surrounded by an electrical insulator, advantageously made of a material resistant to very high temperatures.
• the insulation which is chosen to withstand high temperatures is advantageously cooled by the circulation of water from the current conducting cooling system.
• the invention advantageously proposes to surround the electrical insulator with a second cooling system of the "water-jacket" type. It is thus possible to choose a material for the electrical insulator resistant to lower temperatures. In addition, such a material generally sees its electrical insulation properties improve at low temperature.
• the electrode support thus proposed therefore comprises two cooling systems.
• the cooling systems are advantageously produced by circulating water.
• the internal system being current conductor electric for supplying the electrode, the invention provides two separate water circulation circuits so that the current-carrying water circulating in the cooling system supplying the electrode does not provide a voltage at the level of the second cooling system which would then no longer have any utility.
• the two cooling systems are supplied by the same water circuit, the water being demineralized so that it does not conduct current.
• the device for supplying water outside the electrode support can thus be limited to a single circuit.
• FIGS. 1, 2 and 3 represent:
• FIG. 1 a section of a partial schematic representation of an oven having electrodes immersed vertically from the surface
• FIG. 2 a diagram of an embodiment according to the invention of an electrode and its support.
• FIG. 1 represents part of a melting furnace associated with plunging electrodes 1.
• the furnace is constituted by a refractory basin composed of the bottom 2 and the side walls 3. Above the basin, the refractory vault 4 is suspended from a metal frame 5 partially shown, said metal frame 5 overlapping the oven.
• Movable refractory walls 6 are provided which, when they are in the low position, that is to say resting on the side walls 3, make it possible to partially isolate the molten bath 7 from the surrounding atmosphere.
• the electrode 1 As regards the electrode 1, it is immersed on the surface of the fusion bath 7 under the layer 9 of raw materials to be melted. This layer 9 which covers the fusion bath 7 in normal operating mode, thermally insulates the basin and makes it possible to avoid heat loss.
• the electrode 1 is fixed to the support 8 which comprises the electrical supply system and a device for cooling the electrode 1, which are not shown in this FIG. 1.
• the support 8 is itself connected to a mechanism, not shown, which makes it possible in particular to remove an electrode 1 from the bath, for example for a change or a repair.
• the electrode 1 and its support 8 are more precisely represented and show the advantages of the invention.
• the electrode 1, usually made of molybdenum, is fixed by means of a current conducting element 10 to the tube 11 which constitutes the electric current conducting cooling device.
• the element 10 is an extension which is fixed to the tube 11 by screwing. At the other end of this extension 10, the electrode 1 is fixed.
• Such an embodiment makes it possible to easily disassemble the set extension 10 / electrode 1 because the place of the screwing never dips in the bath. fusion. Indeed, if the tube 11 was longer and came to soak directly in the bath, it would be possible to directly attach the electrode 1 to it, for example by screwing.
• the extension 10 can be surrounded, at least partially, by a refractory material sufficiently thick to avoid direct contact with raw materials or the molten bath.
• the extension 10 also allows the passage of the coolant to the electrode so that it is cooled.
• Screw fixing is interesting because it allows quick replacement. Electrode replacements can be frequent because they do not only intervene in the event of wear but also make it possible to modify the electrodes and in particular their length so as to modify the level of immersion and therefore the energy intake. in the oven.
• the tube 11 can be made of steel so that it has good rigidity and conduction properties.
• a second tube 12 for example concentric.
• This second tube 12 is for example fixed at different points to the internal surface of the tube 11.
• the association of these two tubes 11 and 12 allows water to circulate and thus constitutes a water-type cooling device. jacket.
• the cooling system being designed so as to cool the electrode 1, the tube 12 crosses the extension 10.
• a supply col ⁇ 13 for example copper itself placed within an insulating formwork 14.
• This collar 13 allows to put the tube 11 at the desired voltage, and the latter being electrically conductive, supplying the electrode 1 with this same voltage.
• an electrical insulating material 15 advantageously made of a refractory material of the type of the electrical insulator sold under the reference MURATHERM 500 M.
• the material 15 is made in the form of one or more sleeves which envelop and are supported on a part of the external surface of the tube 11. This electrical insulating material therefore allows access to the electrode support without any risk of electrocution for operators who must approach the weld pool.
• the material 15 is itself surrounded by a concentric envelope 16 in which circulates a cooling liquid such as water.
• This envelope 16 of the "water-jacket" type comprises an internal sleeve 17 which allows the circulation of water.
• This second cooling device makes it possible on the one hand to avoid overheating of the insulating material even if it is chosen as being able to withstand fairly high temperatures and if it is already partly cooled by the first cooling system .
• the various elements cited 11, 12, 15, 16, 17 constitute tubes, for example, concentric, placed around one another.
• a cooling device of the "water-jacket" type, current conductor consisting of two concentric tubes 18, 19 is surrounded by one or more sleeves 20 made of an electrically insulating material and having good thermal insulation and good temperature resistance.
• Thermal protection of the surface of the electrode support is then obtained on the one hand, by the very nature of the sleeve 20 and on the other hand, by the presence of the cooling device which makes it possible to cool this sleeve 20 .
• the electrical protection is provided by the sleeve 20 which envelops the current conducting tube 19.
• the various pipes allowing the arrival and departure of the cooling water are not shown in the figures.
• the water used for cooling is advantageously demineralized water, which makes it possible to use the same circuits for the two cooling systems without the risk of conduction of the current to the external cooling system, which is also connected To the earth.
• the unnumbered arrows indicate the different circuits followed by the coolant.
• the electrode associated with its support thus described according to the invention allows on the one hand a risk-free use in normal operating mode since no accessible device is energized and on the other hand a use without risk of degradation of the support when the oven is put on hold.
• the device composed of the electrode and of its support according to the invention therefore makes it possible to conserve the various advantages, linked to the electrical fusion by electrode immersed from the surface of the fusion bath, which have been listed previously. These are, for example, good thermal yields, good quality of the molten material despite changes in draft, an increase in the life of the furnace because the refractories are less attacked or because it is easy to change an electrode.
• the device according to the invention makes it possible to avoid the presence of fully submerged electrodes for the pilot light periods or else the full-time presence of a protection system avoiding the presence of operators near the elements continuously. under tension.

Landscapes

• Furnace Details (AREA)
• Vertical, Hearth, Or Arc Furnaces (AREA)
• Resistance Heating (AREA)
• Discharge Heating (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=9451431

Family Applications (1)

Country Status (14)

Families Citing this family (6)

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• 1994
  • 1994-09-15 ZA ZA947131A patent/ZA947131B/xx unknown
  • 1994-09-27 CN CN94190735A patent/CN1054960C/zh not_active Expired - Fee Related
  • 1994-09-27 ES ES94928439T patent/ES2202328T3/es not_active Expired - Lifetime
  • 1994-09-27 US US08/424,526 patent/US5596598A/en not_active Expired - Fee Related
  • 1994-09-27 WO PCT/FR1994/001124 patent/WO1995009518A1/fr active IP Right Grant
  • 1994-09-27 EP EP94928439A patent/EP0671116B1/de not_active Expired - Lifetime
  • 1994-09-27 DE DE69432892T patent/DE69432892T2/de not_active Expired - Lifetime
  • 1994-09-27 JP JP51014595A patent/JP3655308B2/ja not_active Expired - Fee Related
  • 1994-09-27 KR KR1019950702248A patent/KR100391193B1/ko not_active IP Right Cessation
  • 1994-09-27 DK DK94928439T patent/DK0671116T3/da active
  • 1994-09-27 CA CA002150236A patent/CA2150236A1/fr not_active Abandoned
  • 1994-09-27 BR BR9405619-6A patent/BR9405619A/pt not_active IP Right Cessation
• 1995
  • 1995-05-22 NO NO19952020A patent/NO313170B1/no not_active IP Right Cessation
  • 1995-05-29 FI FI952603A patent/FI952603A0/fi unknown

Non-Patent Citations (1)

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