US3395237A - Electric resistance furnace - Google Patents

Electric resistance furnace Download PDF

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Publication number
US3395237A
US3395237A US635839A US63583967A US3395237A US 3395237 A US3395237 A US 3395237A US 635839 A US635839 A US 635839A US 63583967 A US63583967 A US 63583967A US 3395237 A US3395237 A US 3395237A
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United States
Prior art keywords
current
circuit
electrodes
furnace
control
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Expired - Lifetime
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US635839A
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English (en)
Inventor
Harold S Orton
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HAROLD S ORTON
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Harold S. Orton
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Priority to US635839A priority Critical patent/US3395237A/en
Priority to GB41386/67A priority patent/GB1161851A/en
Priority to BE704953D priority patent/BE704953A/xx
Priority to DE19671583479 priority patent/DE1583479A1/de
Application granted granted Critical
Publication of US3395237A publication Critical patent/US3395237A/en
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    • 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
    • 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
    • H05B3/0019—Circuit arrangements
    • H05B3/0023—Circuit arrangements for heating by passing the current directly across the material to be heated

Definitions

  • This invention relates to an electric resistance furnace having an even number of vertical electrodes and, for each pair of electrodes, an independent circuit containing a current-control means and a constant voltage source. More specifically, it relates to the use of solid state gated switch controls, particularly silicon controlled rectifiers, as control devices in such furnaces.
  • the electrodes are paired and each pair of electrodes is part of an independent electrode circuit; the current in each circuit is individually controlled.
  • Each circuit is independent in that current cannot flow from one circuit to another circuit except by flowing through the glass, and since the current in each circuit is controlled individually, very little current can flow between circuits by flowing through the glass.
  • control means the ability to maintain the average value of the square of the current at a desired level in spite of variations in the resistance of the melt.
  • FIGURE 1 is a diagrammatic planar view of an electric furnace showing the electrode placement and the basic circuitry.
  • FIGURE 2 is a block diagram of an example of a circuit for actuating gated switch controls, here shown as two silicon controlled rectifiers.
  • My electric furnace may be used to melt any materials which can be resistance melted in an electric furnace.
  • the principal use for my furnace is producing glass, in which case the charge materials are usually mainly sand, soda, and lime plus various minor additives.
  • Detergent base materials such as sodium silicates or metasilicates may also be melted in my furnace.
  • My invention is also applicable to electric booster furnaces, that is, furnaces which are heated with both chemical fuels and electricity. It should be understood that the term electric resistance furnace includes booster furnaces.
  • the electric power used in the furnace must be a1- ternating current; almost any frequency may be used although extremely high or low frequencies should be avoided.
  • My electric resistance furnace is preferably of a square or rectangular design since that design has fewer construction problems and is well-suited for the placement of paired electrodes, although other designs may also be found suitable, as, for example, a circular design.
  • a provision is made for admitting charge materials at one side of the furnace and for tapping the melt at the base of the other side.
  • the electrodes are preferably placed so that a checker board of equal rectangles, preferably squares, is formed.
  • each electrode will be substantially equidistant from at least two other electrodes, which will also be true in other suitable electrode placement schemes.
  • the distance between electrodes will depend upon the characteristics of the compounds being melted and the current supplied to the electrodes.
  • the distance between the furnace walls and the peripheral electrodes should be such that the electrodes are not too close to the walls as the walls will then deteriorate rapidly, and not too far away from the walls as a layer of glass will then solidify on the walls.
  • the closest electrodes should be separated by about 3 feet to 4 feet 6 inches and the peripheral electrodes should be about 2 to 3 feet from the walls.
  • Two electrodes in a circuit need not be adjacent electrodes in the furnace, but they must be close enough for current to flow between them.
  • the electrodes pass through openings in the base of the furnace and are long enough to extend throughout the depth of the melt, but they must not extend into the blanket of charge materials which floats on top of the melt or the electrodes will rapidly deteriorate.
  • Each electrode should also be provided with a water cooled electrode block which is gas purged to further preserve the electrode.
  • the electrodes may be made of molybdenum, graphite, or other suitable materials, but molybdenum is preferred.
  • Each circuit for a pair of electrodes must contain a voltage source and a means for controlling the current, or more exactly, the average value of the square of the current.
  • the voltage source in each circuit is of a constant voltage. If a transformer is used the same core should not be used for the secondary windings of other circuits since variations in the current of one circuit would then affect the current available to other circuits.
  • the current-control means is any means which can control the average value of the square of the current by maintaining it at a desired level in spite of changes in the resistance of the melt. This average value may be controlled in at least two waysby introducing a resistance into the circuit and by breaking the circuit.
  • a resistance may be introduced into the circuit, for example, by using a saturable core reactor as a currentcontrol device, but such a reactor displaces the current vectorially which can mean a low power factor. Moreover, any resistance introduced into the circuit generates heat which is a waste of current and must be dissipated by some means.
  • the preferred method of controlling the average value of the square of the current which avoids the difficulties encountered by introducing a resistance into the circuit, is to break the circuit for short periods of time (the average is a continuous average over a period of time which is substantially longer than the time that the circuit is broken).
  • the average value of the square of the current can be maintained at a constant level even though a greater current may fiow during the time that the circuit is closed.
  • phase angle control the current is permitted to flow from phase angles separated by 180 until the end of each half cycle (180 and 360). For example, a current could flow from every 30 to 180 and every 210 to 360.
  • phase angles due to limitations in present-day electronics, it is very difficult to separate by exactly 180 the two phase angles at which the current begins to flow. If the phase angles are not separated by exactly 180, small amounts of direct current will be generated, creating electrolytic reactions in the furnace which wear the electrodes and blister and seed the melt. At some future time this method of control may become sufficiently precise so that no significant amount of direct current is generated; this method of control will then be more suitable for purposes of this invention.
  • Control of the current by breaking the circuit may also be obtained by breaking the circuit for an equal number of positive half-cycles and negative half-cycles, a procedure known as time proportioned cycle control. That is, for example, the circuit can be opened for one entire cycle and closed for the next entire cycle. I have found that present-day electronics are sutficiently precise so that the current may be controlled by this method without generating direct current.
  • One means for breaking the circuit for short periods using time proportioned cycle control is to use solid state gated switch controls in cooperation with control circuits.
  • Such controls include water-cooled germanium rectifiers and silicon controlled rectifiers (SCRs); SCRs are preferred.
  • Gated switch controls do not pass any current unless they are gated, and when gated each control will pass current in only one direction. Thus, by connecting two 4 or more controls back-to-back in parallel, a current having a complete cycle will flow only when the controls are gated.
  • the gate control is so precise that the gate may be opened and closed in mil-lionths of a second. Although at least two controls are needed to pass a complete cycle, almost any number may be used; the number will depend upon the rating of the control and the power requirements of the furnace.
  • control circuit In cooperation with the gated switch control is a control circuit which activates the control.
  • the resistance of the melt at different temperatures is predetermined.
  • the control circuit is then set to activate the gated switch control when the resistance of the melt falls to level in-dicative of an excessive temperature.
  • an electric furnace container 1 is provided with a batch charger 2 for feeding charge materials and a throat 3 for tapping the melt.
  • Sixteen electrodes 4 extend vertically from the base of the furnace.
  • Each pair of electrodes is in an independent circuit formed with wires 5, the secondary windings of transformers 6, and current-control devices 7.
  • the primary windings of transformers 6 are wired in three different ways to the three lead wires 8, the currents of which are out of phase.
  • FIGURE 2 cuurrent flows from transformer 9 through cable 10 to electrode 11.
  • a means for controlling the current in the circuit using time proportioned cycle control is interposed between the other electrode 12 in the electrode circuit and transformer 9.
  • This means is two SCRs 13 and 14 wired back-to-back in parallel and a control circuit for activating the SCRs.
  • Auto manual control 15 is set for the current desired in the electrode circuit.
  • a signal proportional to the setting is sent to time proportioning amplifier 16 via mixer amplifier 17.
  • Time proportioning amplifier 16 sends pulses back to the mixer amplifier, the number of pulses per second being proportional to the signal from the auto manual control.
  • the mixer amplifier also receives a signal from current transformer 18 which is first rectified by current feedback amplifier 19; this signal is proportional to the current flowing in the electrode circuit.
  • the mixer amplifier mixes the signal from the time proportioning amplifier and the rectified signal from the current transformer using the magnetic flux in the core of a transformer. The resultant signal is then sent to pulse circuit amplifier 20 which splits the signal into two pulsed signals out of phase.
  • Example A furnace of the design shown in FIGURE 1 and having the basic circuitry illustrated by FIGURE 2 was constructed for use with a 2300 volt delta primary three phase voltage source. Eight transformers supplied 120 volts to each independent circuit and the current was controlled with eight pairs of SCRs per circuit. The furnace melted 51 /2 tons of soda-lime container glass every 24 hours. The production was uneventful and melt was unblistered, unseeded, and of good quality.
  • this invention is for. an electric resistance furnace having an even number of vertical electrodes where each pair of electrodes is in an independent circuit which includes a means for controlling the current.
  • An electric resistance furnace comprising:
  • (D) means for controlling the current in each circuit.
  • said means for controlling the current includes at least two solid state gated switch controls wired back-to-back in parallel.
  • said means for controlling the current includes at least two silicon controlled rectifiers wired back-to-back in parallel.
  • An electric resistance furnace comprising:
  • said means for opening and closing said circuits includes at least two solid state gated switch controls wired back-to-back in parallel.
  • said means for opening and closing said circuits includes at least two silicon controlled rectifiers wired back-to-back in parallel.
  • An electric resistance furnace comprising:
  • said electrical means includes at least two solid state gated switch controls wired back-to-back in parallel.
  • said electrical means includes at least two silicon controlled rectifiers wired back-to-back in parallel.
  • An electric resistance furnace including its electrical system, for use with a three phase power source of 0 a substantially constant voltage comprising:
  • each second electrical circuit including the primary windings of a transformer the secondary windings of which are a part of the corresponding independent electrical circuit, and electrical connections to a selected two of the three phases of said power source, said selected two phases being selected for different circuits in a total of three different ways.
  • said means for controlling said current is at least two silicon controlled rectifiers wired back-to-back in parallel.
  • An electric resistance furnace including its electrical system, for use with a three phase power source of a substantially constant voltage comprising:
  • each second electrical circuit including the primary windings of a transformer the secondary windings of which are a part of a corresponding independent electrical circuit, and electrical connections to a selected two of the three phases of said power source, said selected two phases being 7 selected for different circuits in a total of three different ways, each way being selected as nearly as possible the same number of times that each other way is selected.
  • An electric resistance furnace including its electrical system, for use with a three phase power source of a substantially constant voltage comprising:
  • each second electrical circuit including the primary windings of a transformer the secondary windings of which are a part of a corresponding independent electrical circuit, and electrical connections to a selected two of the three phases of said power source, said selected two phases being selected for different circuits in a total of three different ways, each way being selected as nearly as possible the same number of times that each other way is selected.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Furnace Details (AREA)
  • Control Of Resistance Heating (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Glass Melting And Manufacturing (AREA)
US635839A 1967-05-03 1967-05-03 Electric resistance furnace Expired - Lifetime US3395237A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US635839A US3395237A (en) 1967-05-03 1967-05-03 Electric resistance furnace
GB41386/67A GB1161851A (en) 1967-05-03 1967-09-11 Improvements in or relating to Electric Resistance Furnaces.
BE704953D BE704953A (d) 1967-05-03 1967-10-11
DE19671583479 DE1583479A1 (de) 1967-05-03 1967-10-26 Elektrischer Widerstandsofen

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US635839A US3395237A (en) 1967-05-03 1967-05-03 Electric resistance furnace

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US3395237A true US3395237A (en) 1968-07-30

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US635839A Expired - Lifetime US3395237A (en) 1967-05-03 1967-05-03 Electric resistance furnace

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BE (1) BE704953A (d)
DE (1) DE1583479A1 (d)
GB (1) GB1161851A (d)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2003945A1 (de) * 1969-02-03 1970-08-06 Ver E Stahlwerke Ag Anlage zum Elektroschlackenumschmelzen von Metallen,insbesondere von Staehlen
US3619464A (en) * 1970-02-03 1971-11-09 Boehler & Co Ag Geb Apparatus for electroslag remelting of metals and in particular steel
US3806621A (en) * 1971-05-17 1974-04-23 Owens Corning Fiberglass Corp Electric furnace
US3818112A (en) * 1973-04-30 1974-06-18 Corhart Refractories Co Electrical furnace for melting glass
US3836689A (en) * 1972-07-19 1974-09-17 Owens Corning Fiberglass Corp Electric glass furnace with zone temperature control
US3888650A (en) * 1971-10-02 1975-06-10 Elemelt Ltd Glass melting furnaces
US3967046A (en) * 1975-02-18 1976-06-29 Owens-Corning Fiberglas Corporation Apparatus and method for increasing furnace life in an electric furnace for thermoplastic materials
US4025713A (en) * 1974-12-20 1977-05-24 Statni Vyzkumny Ustav Sklarsky Electric glass-melting furnaces
US4049899A (en) * 1975-06-17 1977-09-20 Nippon Electric Glass Company, Limited Apparatus for uniformly heating molten glass
EP0014873A1 (en) * 1979-02-19 1980-09-03 Elettromeccanica Tironi S.r.l. Method of melting vitreous materials and use of the suitable device for the accomplishment of the method
US4324942A (en) * 1980-12-22 1982-04-13 Owens-Corning Fiberglas Corporation Electric glass melting furnace
US4528013A (en) * 1982-08-06 1985-07-09 Owens-Corning Fiberglas Corporation Melting furnaces
US4531218A (en) * 1983-06-17 1985-07-23 Owens-Corning Fiberglas Corporation Glass melting furnace
WO2020023218A1 (en) * 2018-07-27 2020-01-30 Corning Incorporated Methods for heating a metallic vessel in a glass making process
EP4570763A1 (en) * 2023-12-12 2025-06-18 Schott Ag Method and vessel for electrically heating a glass melt
WO2025125354A1 (en) * 2023-12-12 2025-06-19 Schott Ag Method and vessel for electrically heating a glass melt

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2523030A (en) * 1948-10-30 1950-09-19 Glass Fibers Inc Electric glass furnace
US2636913A (en) * 1943-07-01 1953-04-28 Saint Gobain Method and apparatus for the manufacture of glass by electric heating
US2749378A (en) * 1954-01-08 1956-06-05 Harvey L Penberthy Method and apparatus for glass production
US2761890A (en) * 1952-03-15 1956-09-04 Saint Gobain Method and arrangement in the heating of electric furnaces
US2993079A (en) * 1957-04-15 1961-07-18 Owens Illinois Glass Co Electric heating method and apparatus for uniformly heating glass
US3047647A (en) * 1959-10-26 1962-07-31 Hagan Chemicals & Controls Inc Control systems and components thereof
US3182112A (en) * 1962-07-05 1965-05-04 Owens Illinois Glass Co Current balancing means for multiple electrodes in electrically heated glass meltingunits

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636913A (en) * 1943-07-01 1953-04-28 Saint Gobain Method and apparatus for the manufacture of glass by electric heating
US2523030A (en) * 1948-10-30 1950-09-19 Glass Fibers Inc Electric glass furnace
US2761890A (en) * 1952-03-15 1956-09-04 Saint Gobain Method and arrangement in the heating of electric furnaces
US2749378A (en) * 1954-01-08 1956-06-05 Harvey L Penberthy Method and apparatus for glass production
US2993079A (en) * 1957-04-15 1961-07-18 Owens Illinois Glass Co Electric heating method and apparatus for uniformly heating glass
US3047647A (en) * 1959-10-26 1962-07-31 Hagan Chemicals & Controls Inc Control systems and components thereof
US3182112A (en) * 1962-07-05 1965-05-04 Owens Illinois Glass Co Current balancing means for multiple electrodes in electrically heated glass meltingunits

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2003945A1 (de) * 1969-02-03 1970-08-06 Ver E Stahlwerke Ag Anlage zum Elektroschlackenumschmelzen von Metallen,insbesondere von Staehlen
US3619464A (en) * 1970-02-03 1971-11-09 Boehler & Co Ag Geb Apparatus for electroslag remelting of metals and in particular steel
US3806621A (en) * 1971-05-17 1974-04-23 Owens Corning Fiberglass Corp Electric furnace
US3888650A (en) * 1971-10-02 1975-06-10 Elemelt Ltd Glass melting furnaces
US3836689A (en) * 1972-07-19 1974-09-17 Owens Corning Fiberglass Corp Electric glass furnace with zone temperature control
US3818112A (en) * 1973-04-30 1974-06-18 Corhart Refractories Co Electrical furnace for melting glass
JPS5013939A (d) * 1973-04-30 1975-02-13
US4025713A (en) * 1974-12-20 1977-05-24 Statni Vyzkumny Ustav Sklarsky Electric glass-melting furnaces
US3967046A (en) * 1975-02-18 1976-06-29 Owens-Corning Fiberglas Corporation Apparatus and method for increasing furnace life in an electric furnace for thermoplastic materials
US4049899A (en) * 1975-06-17 1977-09-20 Nippon Electric Glass Company, Limited Apparatus for uniformly heating molten glass
EP0014873A1 (en) * 1979-02-19 1980-09-03 Elettromeccanica Tironi S.r.l. Method of melting vitreous materials and use of the suitable device for the accomplishment of the method
US4412334A (en) * 1979-02-19 1983-10-25 Elettromeccanica Tironi S.R.L. Method of melting vitreous materials and use of the suitable device for the accomplishment of the method
US4324942A (en) * 1980-12-22 1982-04-13 Owens-Corning Fiberglas Corporation Electric glass melting furnace
US4528013A (en) * 1982-08-06 1985-07-09 Owens-Corning Fiberglas Corporation Melting furnaces
US4531218A (en) * 1983-06-17 1985-07-23 Owens-Corning Fiberglas Corporation Glass melting furnace
WO2020023218A1 (en) * 2018-07-27 2020-01-30 Corning Incorporated Methods for heating a metallic vessel in a glass making process
CN112638831A (zh) * 2018-07-27 2021-04-09 康宁公司 用于在玻璃制作过程中加热金属容器的方法
CN112638831B (zh) * 2018-07-27 2022-11-04 康宁公司 用于在玻璃制作过程中加热金属容器的方法
TWI812761B (zh) * 2018-07-27 2023-08-21 美商康寧公司 用於在玻璃製作過程中加熱金屬容器的方法
US12043565B2 (en) 2018-07-27 2024-07-23 Corning Incorporated Methods for heating a metallic vessel in a glass making process
TWI856761B (zh) * 2018-07-27 2024-09-21 美商康寧公司 用於在玻璃製作過程中加熱金屬容器的方法
EP4570763A1 (en) * 2023-12-12 2025-06-18 Schott Ag Method and vessel for electrically heating a glass melt
WO2025125354A1 (en) * 2023-12-12 2025-06-19 Schott Ag Method and vessel for electrically heating a glass melt

Also Published As

Publication number Publication date
BE704953A (d) 1968-04-11
GB1161851A (en) 1969-08-20
DE1583479A1 (de) 1970-08-20

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