CA1048273A - Electrically-heated melting furnace with a cooling trough - Google Patents
Electrically-heated melting furnace with a cooling troughInfo
- Publication number
- CA1048273A CA1048273A CA75218380A CA218380A CA1048273A CA 1048273 A CA1048273 A CA 1048273A CA 75218380 A CA75218380 A CA 75218380A CA 218380 A CA218380 A CA 218380A CA 1048273 A CA1048273 A CA 1048273A
- Authority
- CA
- Canada
- Prior art keywords
- trough
- furnace
- tank
- molten material
- cooling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
Landscapes
- Glass Melting And Manufacturing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electronically-heated, glass melting furnace with a cooling trough and with cooling means for the trough is provided.
The furnace is heated by means of electrodes immersed in molted glass in the furnace; particularly as the throughput of the furnace increases, the molten glass becomes hotter. To overcome this, the cooling trough is provided in a portion of the furnace bottom, extending beyond a throat to a riser, with the bottom and the side walls of the trough being exposed to ambient temperatures below the furnace. The resulting heat loss aids in cooling the glass flowing out of the furnace to overcome the inherent heat rise at high throughputs. Cooling means are also provided extending along the trough, with the rate of cooling achieved thereby being capable of selective control. Specifically, an air duct extends along the cooling trough and has outlets spaced therealong directed at the trough bottom to supply cooling air in heat exchanges relationship with the bottom. Electrodes also can extend upwardly through the trough bottom into the trough, the electrodes serving to further cool the trough by providing heat conductive paths from the trough to the ambient conditions below the furnace. The trough electrodes, if desired, can also be heated by an emergency power supply to prevent glass from solidifying in the trough in the event that a major power failure should occur and power to the main heating electrodes is off.
An electronically-heated, glass melting furnace with a cooling trough and with cooling means for the trough is provided.
The furnace is heated by means of electrodes immersed in molted glass in the furnace; particularly as the throughput of the furnace increases, the molten glass becomes hotter. To overcome this, the cooling trough is provided in a portion of the furnace bottom, extending beyond a throat to a riser, with the bottom and the side walls of the trough being exposed to ambient temperatures below the furnace. The resulting heat loss aids in cooling the glass flowing out of the furnace to overcome the inherent heat rise at high throughputs. Cooling means are also provided extending along the trough, with the rate of cooling achieved thereby being capable of selective control. Specifically, an air duct extends along the cooling trough and has outlets spaced therealong directed at the trough bottom to supply cooling air in heat exchanges relationship with the bottom. Electrodes also can extend upwardly through the trough bottom into the trough, the electrodes serving to further cool the trough by providing heat conductive paths from the trough to the ambient conditions below the furnace. The trough electrodes, if desired, can also be heated by an emergency power supply to prevent glass from solidifying in the trough in the event that a major power failure should occur and power to the main heating electrodes is off.
Description
~ 8~73 This invention relates to an electrically-heated, melting furnace having a cooling trough located in the bottom thereof.
Electrically-heated, glass melting furnaces have been known in the art to a limited extent since the early 1900's.
One problem with the earlier furnaces was the lack of effective electrodes by means of which the electric heating could be accomplished. More recently, satisfactory electrodes have been developed. At the same time, electric heating of glass melting lQ furnaces has become more desirable since the electrically-heated furnaces have a particular advantage in substantially eliminating pollution at the glass melting site~ An additional advantage results when the electric power is generated by coal or nuclear fuel, in contrast to burners in conventional glass melting furnaces utilizing relatively scarce gas or oil as the fuel. However, the electric heat also has other advantages, including making it possible to obtain higher quality glass and a hlgh degree of melting efficiency. Better control over the final glass composition can also be achieved, especially when there are more volatiles in the glass batch.
With conventional glass melting furnaces employing combustion burners firing over the molten glass, as the through-put of the furnace increases, the temperature of the glass tends to decrease. With electrically-heated furnaces, however, with the electrodes immersed in the molten glass, an increase in the throughput has been Eound -to result in an increase in the temperature of the molten glass exiting from the furnace.
This invention seeks to provide an electrically-heated glass melting furnace which facilitates achieving a more uniform temperature of the exiting glass even under conditions of varying throughput.
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Accordinc3 to one aspect of this invention there i~
provided a furnace for melting a heat-softenable material, the furnace comprising a tank for holding molten material formed by a bottom, side walls, and end walls, means for supplying batch material over molten material in the tank, means extending into the molten material below the batch material for supplying heat to the molten material, wall means forming a cooling trough centrally located in the bottom of the tank and extending beyond an end wall theréof to discharge molten material from the tank, the wall means being exposed to ambient conditions below the bottom of the tank to dissipate heat from molten material in the trough.
According to another aspect of this invention there is provided a method of operating an electrically~heated melting furnace for melting a heat-softenable material, comprising establishing a pool of molten material in a tank, supplying batch material onto the surface of the pool to ~ :~
establish a layer of batch thereover, heating the molten material below the batch layer, collecting molten material ;~
in a trough in the bottom of the tank, directing the molten material in the trough toward a location beyond the pool, and cooling the molten material in the trough.
A furnace in accordance with an embodiment of the invention has a cooling trough centrally located in the bottom of the furnace .
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~)4~3 tank and extending beyond a discharge end wall of the furnace to a riser. The cooling trough is designed so as to project below the main bottom of the tank, whereby both the sides and bottom oE the trough are exposed -to ambient conditions below the glass melting furnace. The cooling trough thereby presents a substantial surface area from which heat can be dissipated. The cooling trough preferably has a width not exceeding about one~
fourth the width of the furnace bottom, and preferably has a depth at least equal to the wldth to assure substantial protru-sion of the trough below the hottom o~ the tank and a corres-; pondingly substantial degree of heat loss. The trough preferably extends not more than about one-half the distance between the end walls of the tank since the glass near the forward end of the tank has a minimal convection current, and a cooling trough at this portion of the tank would be less effective. The extra length of such a trough would increase the cost of the tank and increase general heat loss without having any real benefit on the cooling of the exiting glass through the trough at the dis-charge end of the tank.
Cooli~g means also extend along the cooling trough and provide a cooling medium in heat exchange relationship with the outer surfaces of the trough. More specifically, the cool-ing means can be in the form of an air duct extending along the trough and having a plurality of outlets directing air into con-tact with an outer surface of the cooling trough. The volume of air then can be controlled to control the extent of cooling of the trough. Temperature-sensing means can be located down~
stream in the trough to sense the temperature of the glass ~,'~ ?, .~ , 1~)41~;~73 flowing therethrough, with a control unit controlling the air volume in response to the temperature. Hence, as the throughput increases and the glass temperature rises, the volume of the cool-ing medium can be increased to correspondingly increase the amount of heat dissipated from -the surfac~sof the trough.
Short electrodes can also be provided for the cooling trough with these electrodes extending through a wall of the trough, preferably the bottom, and having exposed portions below the furnace. The electrodes, being heat conducting, can thereby conduct heat from the molten glass in the trough to the ambient conditions below the furnace. The extent to which the electrodes protrude into the trough can also be controlled, with the degree of cooling by the electrodes there~y regulated. If desired, a power supply, preferably an emergency power supply, can be pro-vided for the trough electrodes. In the event of a main power failure, power can then be supplied to the electrodes to heat the glass in the trough and prevent solidification.
The invention, its objects, and its advantages will be further understood from the following detailed description of a ;~ `
preferred embodiment thereof, reference being made to the accom~
panying drawings, in which:
Fig. 1 is a schematic, fragmentary view in longitudinal cross section of a furnace embodying the invention;
Fig. 2 is a schematic, fragmentary, plan view of the furnace of Fig. 1, without glass in the furnace;
Fig. 3 is a schematic view in transverse cross section taken through the furnace of Figs. 1 and 2; and Fig. 4 is a greatly enlarged view of a portion of the furnace of Fig. 3, and showing certain additional details.
Referring to the drawings, and particularly to Figs. 1 and 2, an overall melting furnace embodying the invention is s, ,~
indicated at 10. The furnace is illustrated in connection with glass melting operations, although the furnace according to the invention can also be used to advantage in the melting of other materials. The furnace supplies molten ylass to a riser 12, located beyond the discharge end, and to a conditioning chamber 14 and a forehearth 16. From the forehearth, the molten glass can be supplied through openin~s 18 to suitable fiber-for~ing devices 20 located therebelow. Of coursel the furnace according to the invention is not limited to supplying glass for fiber-forming operations.
The furnace 10 includes a glass melting tank 22 formedby side walls 24, a foxward end wall 28, a rear or dis-charge end wall 30, and a main bottom 32. A suitable roof tnot shown) can be supported above the tank 22. Heating means for melting glass or other batch in the furnace 10 include a plural-ity of electrodes 34 extending upwardly into the tank 22 from a lower level through the bottom 32. The electrodes 34 are preferably positioned in a symmetrical manner with respect to a center line extending longitudinally through the tank 22, with electrodes toward the forward half of the tank being substan-tially uniformly spaced apart, and with those toward the dis-charge half of the tank being spaced farther apart at the center of the tank than at the sides. The portions of the electrodes 34 exposed below the tank bottom 32 can be protected by suitable sleeves containing an inert gas, and the electrodes can also be water cooled, as is well known in the art. Power is supplied to the electrodes 34 through suitable leads from a suitable power source (not shown).
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The portions of the electrodes 34 within the tank 22 are totally immersed in a pool of molten glass 36, with the upper ends of the electrodes typically being about ten inches below the surface of the molten glass 36. Additional glass batch is c~n~
tinually supplied over the molten glass 36 to form a batch layer 38 thereon which also serves as an effective in~ulating layer on the molten glass. The batch can be supplied ~rom a batch car-riage 40 which extends across the entire wldth of the tank 22 between the side walls 24 and is reciprocated back and forth substantially over the length of the tank. A carriage of this nature is disclosed more full~ in U.~ patent No.3,877,917 issued April 15, 1975 in the name of Charles M. Hohman. The car-riage can include one or more vibratory feeders to regulate the rate of feed of the batch from the carriage 40 to the layer 38.
When the output of the fiber-forming units 20 or other glass forming devices is increased, the throughput of the furnace 10 also must be increased. To accomplish this, more electrical power is supplied to the electrodes 34 and a larger : . . . .
quantity of batch is fed from the carriage 40. Since the 20- heating means or electrodes are entirely immersed within the molten glass 36, the increased throughput with the increased power to the electrodes 34 results in a higher temperature in the molten glass supplied to the forehearth 16. This can be detrimental to the fiber-forming operation or other operation, particularly where the forehearth glass temperature is critical, as is true of fiber-forming operations. To achieve a more uni-form glass temperature in the forehearth 16, in spite of increased glass pull or throughput, a cooling trough 42 in accordance with the invention is provided in the bottom of the B ::
tank 22. The trough 42 is formed by wall means indicated at 44 protruding below the bottom 32 of the tank 22, the wall means 44 constituting two side walls 46 and 48 (see ~igs. 3 and 4) and a bottom wall 50. These walls present three surfaces exposed to ambient conditions below the tank 22 to provide substantial heat loss to the ambient from the trough 42. The width of the trough 42 preferably is from one-sixth to one-fourth the width of the tank 22, with the depth of the trough preferably being at least equal to the width to provide adequate heat loss through the walls 46 and 48 and the bottom 50. The trough 42 is of a length sufficient to extend to the riser 12 past a throat 52 located between the tank and the riser. At the other end, the trough 42 prefexably extends no more than about half the distance between the discharge end wall 30 and the forward end wall 28. Any shorter distance does not enable sufficient cooling to occur in the trough 42. If the trough extended further toward the forward end wall 28, it would not have any substantial beneficial cooling effect, particularly since convection currents in the - molten glass toward the forward end are minimal. Consequently, -the coolest glass would not necessarily collect in the trough to any noticeable extent toward the forward end. Thus, an extra length of the trough toward the forward end wall would only generally increase heat loss and result in higher construction costs for the furnace. Toward the discharge end of the tank 22, convection currents are more pronounced ~Fig. 3) with the coolest glass collecting in the trough 42, thus reducing the cooling requirements for the glass flowing in a stream through the trough 42.
~ .
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Cooling means are provided for the trough 42 to enable the cooling effect on the glass flowing through the trough to change as the throughput changes. In a preferred form, the cooling means in accordance with the invention are indicated at 54 and include a main duct 56 extendiny longitudinally of the trough 42 and a plurality of branch outlets 58 communicating therewith and directing a cooling m~dium, specifically air, toward the bottom 50 of the wall means 44. The cooling medium or air can be supplied by a suitable blower 60 (Fig. 1), with the volume of the air controlled by a damper or valve 62~ The flow-control damper 62 can be opened more as the throughput oE
the furnace 10 increases and the ~lass discharged therefrom tends to increase in temperature. A higher volume of the air is then directed through the outlets 58 toward the bottom 50 of the trough thereby to increase the dissipation of heat from the trough and produce a greater cooling effect on the molten glass flowin~ therethrough. ~?
The damper 62 can be automatically controlled, if desired. For this purpose, a temperature-sensing device or thermocouple 64 is located in the trough 42 toward the down-stream end thereof with the device 64 being connected to a temperature controller 66. This, in turn, operates a control motor 68 which is operatively connected to the damper 62 so as to tend to close the damper 62 as the temperature sensed by the thermocouple 64 decreases and to open the damper 62 as the temperature sensed by the thermocouple 64 increases. The com-ponents 64, 66 and 68 are commerclally available devices and -~
are not discussed in detail.
)4~ 3 Also, in accordance with the invention, a plurality of short electrodes 70 can be loca-ted in the trough 4 , extending upwardly through the bottom 50 of the wall means 44. By them-selves, the electrodes 70 are heat-conducting elements which can serve to cool the glass by conducting heat in the glass in the trough 42 to ambient conditions below the tank 22. If desired, each of the electrodes 70 can ba provided with a gear drive 72 (Fig. 4) and a motor 74, by means of which the electrodes 70 can be raised so as to protrude further into the trough 42, or lowered so as to have a shorter length immersed in the trough.
With this arrangement, the extent of the cooling effect of the electrodes 70 can be controlled. As the extent of protrusion of the electrodes into the trough increases, the cooling effect of the electrodes on the glass flowing through the trough also increases, as long as a sufficient portion o the length remains exposed so as to dlssipate heat adequately. The streams of cooling air supplied by the outlets 58 can be directed-at the exposed portions of the electrodes 70 below the bottom 50, if desired, to increase the rate of conduction of heat away from the glass in the trough by means of the electrodes.
If desired, the electrodes 70 can also be connected to a power supply as indicated in Fig. 4, preferably an emer-; gency power supply. In the event of a main power failure for the electrodes 34, the emergency power supply can be used to heat the electrodes 70 and thereby maintain the glass in the trough 42 in a molten condition under emergency conditions.
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Electrically-heated, glass melting furnaces have been known in the art to a limited extent since the early 1900's.
One problem with the earlier furnaces was the lack of effective electrodes by means of which the electric heating could be accomplished. More recently, satisfactory electrodes have been developed. At the same time, electric heating of glass melting lQ furnaces has become more desirable since the electrically-heated furnaces have a particular advantage in substantially eliminating pollution at the glass melting site~ An additional advantage results when the electric power is generated by coal or nuclear fuel, in contrast to burners in conventional glass melting furnaces utilizing relatively scarce gas or oil as the fuel. However, the electric heat also has other advantages, including making it possible to obtain higher quality glass and a hlgh degree of melting efficiency. Better control over the final glass composition can also be achieved, especially when there are more volatiles in the glass batch.
With conventional glass melting furnaces employing combustion burners firing over the molten glass, as the through-put of the furnace increases, the temperature of the glass tends to decrease. With electrically-heated furnaces, however, with the electrodes immersed in the molten glass, an increase in the throughput has been Eound -to result in an increase in the temperature of the molten glass exiting from the furnace.
This invention seeks to provide an electrically-heated glass melting furnace which facilitates achieving a more uniform temperature of the exiting glass even under conditions of varying throughput.
.
~48~7~ :
Accordinc3 to one aspect of this invention there i~
provided a furnace for melting a heat-softenable material, the furnace comprising a tank for holding molten material formed by a bottom, side walls, and end walls, means for supplying batch material over molten material in the tank, means extending into the molten material below the batch material for supplying heat to the molten material, wall means forming a cooling trough centrally located in the bottom of the tank and extending beyond an end wall theréof to discharge molten material from the tank, the wall means being exposed to ambient conditions below the bottom of the tank to dissipate heat from molten material in the trough.
According to another aspect of this invention there is provided a method of operating an electrically~heated melting furnace for melting a heat-softenable material, comprising establishing a pool of molten material in a tank, supplying batch material onto the surface of the pool to ~ :~
establish a layer of batch thereover, heating the molten material below the batch layer, collecting molten material ;~
in a trough in the bottom of the tank, directing the molten material in the trough toward a location beyond the pool, and cooling the molten material in the trough.
A furnace in accordance with an embodiment of the invention has a cooling trough centrally located in the bottom of the furnace .
.. .
.~ ~
~)4~3 tank and extending beyond a discharge end wall of the furnace to a riser. The cooling trough is designed so as to project below the main bottom of the tank, whereby both the sides and bottom oE the trough are exposed -to ambient conditions below the glass melting furnace. The cooling trough thereby presents a substantial surface area from which heat can be dissipated. The cooling trough preferably has a width not exceeding about one~
fourth the width of the furnace bottom, and preferably has a depth at least equal to the wldth to assure substantial protru-sion of the trough below the hottom o~ the tank and a corres-; pondingly substantial degree of heat loss. The trough preferably extends not more than about one-half the distance between the end walls of the tank since the glass near the forward end of the tank has a minimal convection current, and a cooling trough at this portion of the tank would be less effective. The extra length of such a trough would increase the cost of the tank and increase general heat loss without having any real benefit on the cooling of the exiting glass through the trough at the dis-charge end of the tank.
Cooli~g means also extend along the cooling trough and provide a cooling medium in heat exchange relationship with the outer surfaces of the trough. More specifically, the cool-ing means can be in the form of an air duct extending along the trough and having a plurality of outlets directing air into con-tact with an outer surface of the cooling trough. The volume of air then can be controlled to control the extent of cooling of the trough. Temperature-sensing means can be located down~
stream in the trough to sense the temperature of the glass ~,'~ ?, .~ , 1~)41~;~73 flowing therethrough, with a control unit controlling the air volume in response to the temperature. Hence, as the throughput increases and the glass temperature rises, the volume of the cool-ing medium can be increased to correspondingly increase the amount of heat dissipated from -the surfac~sof the trough.
Short electrodes can also be provided for the cooling trough with these electrodes extending through a wall of the trough, preferably the bottom, and having exposed portions below the furnace. The electrodes, being heat conducting, can thereby conduct heat from the molten glass in the trough to the ambient conditions below the furnace. The extent to which the electrodes protrude into the trough can also be controlled, with the degree of cooling by the electrodes there~y regulated. If desired, a power supply, preferably an emergency power supply, can be pro-vided for the trough electrodes. In the event of a main power failure, power can then be supplied to the electrodes to heat the glass in the trough and prevent solidification.
The invention, its objects, and its advantages will be further understood from the following detailed description of a ;~ `
preferred embodiment thereof, reference being made to the accom~
panying drawings, in which:
Fig. 1 is a schematic, fragmentary view in longitudinal cross section of a furnace embodying the invention;
Fig. 2 is a schematic, fragmentary, plan view of the furnace of Fig. 1, without glass in the furnace;
Fig. 3 is a schematic view in transverse cross section taken through the furnace of Figs. 1 and 2; and Fig. 4 is a greatly enlarged view of a portion of the furnace of Fig. 3, and showing certain additional details.
Referring to the drawings, and particularly to Figs. 1 and 2, an overall melting furnace embodying the invention is s, ,~
indicated at 10. The furnace is illustrated in connection with glass melting operations, although the furnace according to the invention can also be used to advantage in the melting of other materials. The furnace supplies molten ylass to a riser 12, located beyond the discharge end, and to a conditioning chamber 14 and a forehearth 16. From the forehearth, the molten glass can be supplied through openin~s 18 to suitable fiber-for~ing devices 20 located therebelow. Of coursel the furnace according to the invention is not limited to supplying glass for fiber-forming operations.
The furnace 10 includes a glass melting tank 22 formedby side walls 24, a foxward end wall 28, a rear or dis-charge end wall 30, and a main bottom 32. A suitable roof tnot shown) can be supported above the tank 22. Heating means for melting glass or other batch in the furnace 10 include a plural-ity of electrodes 34 extending upwardly into the tank 22 from a lower level through the bottom 32. The electrodes 34 are preferably positioned in a symmetrical manner with respect to a center line extending longitudinally through the tank 22, with electrodes toward the forward half of the tank being substan-tially uniformly spaced apart, and with those toward the dis-charge half of the tank being spaced farther apart at the center of the tank than at the sides. The portions of the electrodes 34 exposed below the tank bottom 32 can be protected by suitable sleeves containing an inert gas, and the electrodes can also be water cooled, as is well known in the art. Power is supplied to the electrodes 34 through suitable leads from a suitable power source (not shown).
,............. .
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The portions of the electrodes 34 within the tank 22 are totally immersed in a pool of molten glass 36, with the upper ends of the electrodes typically being about ten inches below the surface of the molten glass 36. Additional glass batch is c~n~
tinually supplied over the molten glass 36 to form a batch layer 38 thereon which also serves as an effective in~ulating layer on the molten glass. The batch can be supplied ~rom a batch car-riage 40 which extends across the entire wldth of the tank 22 between the side walls 24 and is reciprocated back and forth substantially over the length of the tank. A carriage of this nature is disclosed more full~ in U.~ patent No.3,877,917 issued April 15, 1975 in the name of Charles M. Hohman. The car-riage can include one or more vibratory feeders to regulate the rate of feed of the batch from the carriage 40 to the layer 38.
When the output of the fiber-forming units 20 or other glass forming devices is increased, the throughput of the furnace 10 also must be increased. To accomplish this, more electrical power is supplied to the electrodes 34 and a larger : . . . .
quantity of batch is fed from the carriage 40. Since the 20- heating means or electrodes are entirely immersed within the molten glass 36, the increased throughput with the increased power to the electrodes 34 results in a higher temperature in the molten glass supplied to the forehearth 16. This can be detrimental to the fiber-forming operation or other operation, particularly where the forehearth glass temperature is critical, as is true of fiber-forming operations. To achieve a more uni-form glass temperature in the forehearth 16, in spite of increased glass pull or throughput, a cooling trough 42 in accordance with the invention is provided in the bottom of the B ::
tank 22. The trough 42 is formed by wall means indicated at 44 protruding below the bottom 32 of the tank 22, the wall means 44 constituting two side walls 46 and 48 (see ~igs. 3 and 4) and a bottom wall 50. These walls present three surfaces exposed to ambient conditions below the tank 22 to provide substantial heat loss to the ambient from the trough 42. The width of the trough 42 preferably is from one-sixth to one-fourth the width of the tank 22, with the depth of the trough preferably being at least equal to the width to provide adequate heat loss through the walls 46 and 48 and the bottom 50. The trough 42 is of a length sufficient to extend to the riser 12 past a throat 52 located between the tank and the riser. At the other end, the trough 42 prefexably extends no more than about half the distance between the discharge end wall 30 and the forward end wall 28. Any shorter distance does not enable sufficient cooling to occur in the trough 42. If the trough extended further toward the forward end wall 28, it would not have any substantial beneficial cooling effect, particularly since convection currents in the - molten glass toward the forward end are minimal. Consequently, -the coolest glass would not necessarily collect in the trough to any noticeable extent toward the forward end. Thus, an extra length of the trough toward the forward end wall would only generally increase heat loss and result in higher construction costs for the furnace. Toward the discharge end of the tank 22, convection currents are more pronounced ~Fig. 3) with the coolest glass collecting in the trough 42, thus reducing the cooling requirements for the glass flowing in a stream through the trough 42.
~ .
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Cooling means are provided for the trough 42 to enable the cooling effect on the glass flowing through the trough to change as the throughput changes. In a preferred form, the cooling means in accordance with the invention are indicated at 54 and include a main duct 56 extendiny longitudinally of the trough 42 and a plurality of branch outlets 58 communicating therewith and directing a cooling m~dium, specifically air, toward the bottom 50 of the wall means 44. The cooling medium or air can be supplied by a suitable blower 60 (Fig. 1), with the volume of the air controlled by a damper or valve 62~ The flow-control damper 62 can be opened more as the throughput oE
the furnace 10 increases and the ~lass discharged therefrom tends to increase in temperature. A higher volume of the air is then directed through the outlets 58 toward the bottom 50 of the trough thereby to increase the dissipation of heat from the trough and produce a greater cooling effect on the molten glass flowin~ therethrough. ~?
The damper 62 can be automatically controlled, if desired. For this purpose, a temperature-sensing device or thermocouple 64 is located in the trough 42 toward the down-stream end thereof with the device 64 being connected to a temperature controller 66. This, in turn, operates a control motor 68 which is operatively connected to the damper 62 so as to tend to close the damper 62 as the temperature sensed by the thermocouple 64 decreases and to open the damper 62 as the temperature sensed by the thermocouple 64 increases. The com-ponents 64, 66 and 68 are commerclally available devices and -~
are not discussed in detail.
)4~ 3 Also, in accordance with the invention, a plurality of short electrodes 70 can be loca-ted in the trough 4 , extending upwardly through the bottom 50 of the wall means 44. By them-selves, the electrodes 70 are heat-conducting elements which can serve to cool the glass by conducting heat in the glass in the trough 42 to ambient conditions below the tank 22. If desired, each of the electrodes 70 can ba provided with a gear drive 72 (Fig. 4) and a motor 74, by means of which the electrodes 70 can be raised so as to protrude further into the trough 42, or lowered so as to have a shorter length immersed in the trough.
With this arrangement, the extent of the cooling effect of the electrodes 70 can be controlled. As the extent of protrusion of the electrodes into the trough increases, the cooling effect of the electrodes on the glass flowing through the trough also increases, as long as a sufficient portion o the length remains exposed so as to dlssipate heat adequately. The streams of cooling air supplied by the outlets 58 can be directed-at the exposed portions of the electrodes 70 below the bottom 50, if desired, to increase the rate of conduction of heat away from the glass in the trough by means of the electrodes.
If desired, the electrodes 70 can also be connected to a power supply as indicated in Fig. 4, preferably an emer-; gency power supply. In the event of a main power failure for the electrodes 34, the emergency power supply can be used to heat the electrodes 70 and thereby maintain the glass in the trough 42 in a molten condition under emergency conditions.
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Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED A
1. A furnace for melting a heat-softenable material, said furnace comprising a tank for holding molten material formed by a bottom, side walls, and end walls, means for supplying batch material over molten material in the tank, means extend-ing into the molten material below the batch material for supplying heat to the molten material, wall means forming a cooling trough centrally located in the bottom of the tank and extending beyond an end wall thereof to discharge molten material from the tank, said wall means being exposed to ambient conditions below the bottom of said tank to dissipate heat from molten material in said trough.
2. A furnace according to claim 1 and comprising cooling means extending along said trough and effective to supply a cooling medium in heat exchange relationship with an external surface of said wall means.
3. A furnace according to claim 2 and comprising means for varying the quantity of the cooling medium carried by said cooling means.
4. A furnace according to claim 3 and comprising temperature-sensing means associated with said trough and control means connected to said temperature-sensing means and to said quantity varying means for controlling the quantity of the cooling medium carried by said cooling means in response to the temperature sensed by the sensing means.
5. A furnace according to claim 1 and comprising a plurality of electrodes extending into said trough and being capable of conducting heat away from molten material in said trough to ambient conditions below said tank bottom.
6. A furnace according to claim 5 wherein each of said electrodes has a portion extending into said trough for contact with molten material therein and a portion extending downwardly outside said trough for contact with air below said tank bottom,
7. A furnace according to claim 5 or 6 and comprising means connected to said electrodes to control the extent to which they extend into said trough.
8. A furnace according to claim 5 or 6 and comprising means for connecting said electrodes to an emergency power supply.
9. A furnace according to claim 1, 2, or 3 wherein said wall means forming a cooling trough comprises a bottom and two sides extending below the bottom of said tank and exposed to ambient conditions below the bottom of said tank.
10. A furnace according to claim 4, 5, or 6 wherein said wall means forming a cooling trough comprises a bottom and two sides extending below the bottom of said tank and exposed to ambient conditions below the bottom of said tank.
11. A furnace according to claim 1, 2, or 3 wherein said furnace is an electrically-heated glass melting furnace, the means for supplying heat to the molten material comprises a plurality of electrodes extending upwardly through the bottom of said tank in a predetermined pattern, the furnace further comprising means forming a riser beyond said end wall of the tank, said trough extending beyond said end wall to said riser and extending from said end wall not more than about half the distance toward the other end wall.
12. A furnace according to claim 4, 5, or 6 wherein said furnace is an electrically-heated glass melting furnace, the means for supplying heat to the molten material comprises a plurality of electrodes extending upwardly through the bottom of said tank in a predetermined pattern, the furnace further comprising means forming a riser beyond said end wall of the tank, said trough extending beyond said end wall to said riser and extending from said end wall not more than about half the distance toward the other end wall.
13. A furnace according to claim 1, 2, or 3 wherein said furnace is an electrically-heated glass melting furnace, the means for supplying heat to the molten material comprises a plurality of electrodes extending upwardly through the bottom of said tank in a predetermined pattern, the furnace further comprising means forming a riser beyond said end wall of the tank, and wherein said wall means forming a trough comprises a bottom and two sides extending below the bottom of said tank and exposed to ambient conditions below the bottom of said tank, said trough extending beyond said end wall to said riser and extending from said end wall not more than about half the distance toward the other end wall.
14. A furnace according to claim 4, 5, or 6 wherein said furnace is an electrically-heated glass melting furnace, the means for supplying heat to the molten material comprises a plurality of electrodes extending upwardly through the bottom of said tank in a predetermined pattern, the furnace further comprising means forming a riser beyond said end wall of the tank, and wherein said wall means forming a trough comprises a bottom and two sides extending below the bottom of said tank and exposed to ambient conditions below the bottom of said tank, said trough extending beyond said end wall to said riser and extending from said end wall not more than about half the distance toward the other end wall,
15. A method of operating an electrically-heated melting furnace for melting a heat-softenable material, comprising establishing a pool of molten material in a tank, supplying batch material onto the surface of the pool to establish a layer of batch thereover, heating the molten material below the batch layer, collecting molten material in a trough in the bottom of the tank, directing the molten material in the trough toward a location beyond the pool, and cooling the molten material in the trough.
16. A method according to claim 15 wherein the molten material in the trough is cooled by directing a cooling medium in heat-exchange relationship with the trough from a location outside the trough.
17. A method according to claim 15 or 16 wherein the molten material in the trough is cooled by projecting a heat-conduct-ing body into the trough from a location outside the trough.
18. A method according to claim 15 wherein the molten material in the trough is cooled by projecting a heat-conducting body into the trough from a location outside the trough and direct-ing a cooling medium in heat-exchange relationship with a portion of the heat conducting body located outside the trough.
19. A method according to claim 16 or 18 and comprising sensing the temperature of the molten material near the down-stream end of the trough and controlling the volume of the cooling medium in response to the temperature sensed.
20. A method according to claim 15, 16, or 18 wherein said heat-softenable material is glass.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA308,287A CA1072166A (en) | 1974-02-22 | 1978-07-27 | Electrically-heated melting furnace with a cooling trough |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US445036A US3891422A (en) | 1974-02-22 | 1974-02-22 | Electrically-heated melting furnace with melt cooling means |
| US445037A US3897234A (en) | 1974-02-22 | 1974-02-22 | Method and apparatus for cooling electrically-heated melting furnace |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1048273A true CA1048273A (en) | 1979-02-13 |
Family
ID=27034153
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA75218380A Expired CA1048273A (en) | 1974-02-22 | 1975-01-21 | Electrically-heated melting furnace with a cooling trough |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1048273A (en) |
-
1975
- 1975-01-21 CA CA75218380A patent/CA1048273A/en not_active Expired
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