ELECTRIC BOOSTING SYSTEM FOR A MELTER OF A GLASS MELTING FURNACE
Field of the Invention
The present invention relates to a melter of a glass
melting furnace; and more particularly, to an electric
boosting system for a melter of a glass melting furnace,
which supplies heat needed for melting raw materials for
glass by generating electrical resistance heat of molten
glass.
Background of the Invention
As well known, a panel and a funnel for use in a cathode ray tube is manufactured by press forming a lump of molten glass called a glass gob, wherein the molten glass is produced by melting raw materials for glass, so called a batch, by a glass melting furnace. The glass melting furnace includes a melter for melting the glass raw materials to make the molten glass, a throat for discharging the molten glass from the melter, a refiner for rendering the molten glass bubble-free and compositionally homogeneous, a plurality of forehearths for rendering the molten glass compositionally and thermally homogeneous, and a feeder for supplying the molten glass to a forming equipment for the
panel or the funnel, wherein aforementioned all parts are connected consecutively one after another.
In general, the melter of the glass melting furnace is provided with a bottom, sidewalls, a back wall having a dog house through which the batch is charged into the melter, a front wall forming a border between the melter and the throat, and an arched crown. Each of the sidewall has a sideflux (or a lower basin wall) for containing the molten glass and a breast wall built on the top of the sideflux. And a plurality of ports are formed in the breast wall to communicate with a regenerator.
Further, the melter can be divided into an upstream heating zone where the glass raw materials are melt, a downstream cooling zone where the temperature of the molten glass is controlled, and a hot spot zone interposed between the heating zone and the cooling zone. The hot spot zone includes a hot spot where the molten glass's temperature reaches its highest level. Gas/oxygen burners are installed as a heating device in a portion of the regenerator corresponding to the heating zone. To a portion of the regenerator corresponding to the cooling zone, cooling air is supplied to cool down the melter.
In the conventional melter of the glass melting furnace with such a configuration, heat generated by combustion of the burners is supplied to an upper portion of the melter through the ports, and the glass raw materials
are melted by radiant heat. The efficiency of the glass melting furnace is determined depending on quality level and production amount of the molten glass, and a proper production amount of the melter can be represented by the ability of production of the molten glass per unit area. To increase the production amount of the glass melting furnace requires an increased supply of heat. However, in such a case, heat efficiency of radiant heat generated by combustion of the burners and used to melt the glass raw materials becomes low, and particularly, there exists the combustion capacity limitation of the burners. Therefore, there has been a problem that it is difficult to increase the production amount. Further, increasing heat supply causes a variety of problems including that a large amount of fuel is consumed, thereby deteriorating economical efficiency, that the lifespan of the burners is shortened and that the lifespan of the glass melting furnace is also shortened since the erosion of the melter is accelerated.
In the mean while, flow of the molten glass influences its quality greatly. So, the temperature of the melter should be controlled in several zones in order that the molten glass becomes thermally, chemically and physically homogeneous by keeping the flow of the molten glass stable. However, the radiant heat is difficult to control in several zones, thus causing a problem that there will occur defects in the molten glass.
Summary of the Invention
It is, therefore, an object of the present invention to provide an electric boosting system for a melter of a glass melting furnace, which is capable of improving efficiency of the glass melting furnace by additionally supplying heat by using molybdenum electrode bars to increase its production amount.
It is another object of the present invention to provide an electric boosting system for a melter of a glass melting furnace, which is capable of controlling conveniently and precisely flow of the molten glass by forming a bubble barrier at a hot spot, thus improving quality of the molten glass.
It is still another object of the present invention to provide an electric boosting system for a melter of a glass melting furnace, which is capable of guaranteeing lifespans of the melter and burners.
In accordance with the present invention, there is provided an electric boosting system for a melter of a glass melting furnace, the melter having a heating zone, a hot spot zone and a cooling zone for melting glass raw materials charged into a batch zone through a dog house to form a molten glass, the electric boosting system including: a plurality of molybdenum electrode bars, provided at the
heating zone and the cooling zone, for generating electric resistance heat of the molten glass, the plurality of molybdenum electrode bars being disposed at a bottom of the melter and installed along two opposite side end portions of the bottom of the melter so as to face each other; and a power supply connected to the molybdenum electrode bars to apply thereto a power needed for operation of the molybdenum electrode bars.
Brief Description of the Drawings
The above and other objects and features of the
present invention will become apparent from the following
description of preferred embodiments given in conjunction
v with the accompanying drawings, in which:
Fig. 1 is a schematic vertical cross sectional view of a glass melting furnace using an electronic boosting system in accordance with a preferred embodiment of the present invention;
Fig. 2 presents a schematic horizontal cross sectional view of the glass melting furnace shown in Fig. 1; and
Fig. 3 depicts a diagram of the electric boosting system in accordance with the preferred embodiment of the present invention.
Detailed Description of the Preferred Embodiments
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein like parts appearing Figs. 1 to 3 are represented by like reference numerals.
Referring to Figs. 1 and 2, a glass melting furnace in accordance with the preferred embodiment of the present invention includes a melter 10 for melting glass raw materials B charged thereinto; a throat 20, connected to a downstream end of the melter 10, for discharging a molten glass G from the melter 10; and a refiner 30, connected to a downstream end of the throat 20, for removing bubbles generated inside the molten glass G and making the molten glass G homogeneous.
The melter 10 is built of a bottom 11, sidewalls 12, a back wall 14 having a dog house 13 through which the glass raw materials B are charged into the melter 10, a front wall 15 serving as a border between the melter 10 and the throat 20, and an arched crown 16. Each of the sidewalls 12 has a sideflux (or a lower basin wall) 12a for containing the molten glass G and a breast wall 12b built on the top of the sideflux 12a to support the crown 16. And a plurality of ports 18, which communicate with a plurality of regenerators 17, are formed in the breast walls 12b of the sidewalls 12. Burners (not shown), well known as a heating device, are
installed in the regenerators 17. Flames generated by the operation of the heating device are emitted to the melter 10 through the ports 18 to melt the glass raw materials B.
In the mean while, the glass raw materials B charged into the melter 10 through the dog house 13 immediately begins to melt and flow. Since the molten glass G in the melter 10 continuously flows, it is impossible to accurately determine a point of time when the glass raw materials B melt completely. However, in most cases, it is considered that the melting of the glass raw materials B is completed when the glass raw materials B disappear from a surface of the molten glass G. The region where the glass raw materials B disappear is called a hot spot zone Zl including a hot spot. The hot spot zone Zl intervenes between an upstream heating zone Z2 and a downstream cooling zone Z3, which have different temperature distributions to facilitate convection current of the molten glass G in the melter 10, wherein the convection current is divided into two portions by the hot spot zone Zl interposed between the two portions.
In the heating zone Z2, the convection current of the molten glass G has a rear roll Gl, a flow circulating anticlockwise, while in the cooling zone Z3, there is a front roll G2, a flow circulating clockwise. And, in the hot spot zone Zl, the convection current of the molten glass G has a hot spring G3, an upward flow from the bottom of the melter 10. The molten glass G at the hot spot of the hot

spot zone Zl reaches the maximum temperature. As a result of the aforementioned convection current of the molten glass G in the melter 10, the upstream region from the hot spot Zl serves as a melting zone where the glass raw materials B are melted, while the downstream region from the hot spot Z serves as a refining zone where the molten glass G becomes homogeneous thermally, chemically and physically. The hot spot zone Zl blocks the flowing of the glass raw materials B not yet melted into the cooling zone Z3, while strengthening the convection current of the molten glass G in such a manner as to promote the melting.
Referring to Figs. 1 and 3, a plurality of molybdenum electrode bars 40 formed of molybdenum (Mo) are installed in the melter 10 along two opposite side end portions of the bottom 11 in two lines. The molybdenum electrode bars 40 penetrate the bottom 11 in such a manner that the two lines of the molybdenum electrode bars 40 are disposed along the two opposite side end portions of the bottom 11, respectively, so as to face each other. If a diameter of the molybdenum electrode bar 40 is less than a predetermined value, the molybdenum electrode bar 40 would be readily damaged by its reaction with metallic components in the molten glass G and by thermal shocks. Thus, it could not be used even during one operation period of the glass melting furnace. Further, it is almost impossible to shape molybdenum into a long bar with a diameter greater than a
predetermined value due to its physical properties. Therefore, the molybdenum electrode bar 40 should be made to have the diameter within a predetermined range. Although there is shown in Figs. 1 and 2 that every twelve molybdenum electrode bars 40 are arranged in a line in the upstream and the downstream regions from the hot spot zone Zl, the number of the molybdenum electrode bars 40 can be appropriately increased or decreased according to the need. And, a ground electrode (not shown) having a polarity opposite that of the molybdenum electrode bars 40 is usually connected to the melter 10.
More particularly, the molybdenum electrode bars 40 are inserted into through holes 11a (see Fig. 3) formed in the bottom 11 to protrude into the inside of the melter 10, and a gap between the through hole 11a and the molybdenum electrode bar 40 is sealed with glass.
Referring to Fig. 3, the electric boosting system in accordance with the preferred embodiment of the present invention includes a power supply 50 for supplying power needed to operate the molybdenum electrode bars 40; and a plurality of balancing transformers 51 (51-1, 51-2, •••, 51-n) which are connected between the molybdenum electrode bars 40 and the power supply 50 so as to control currents applied to the individual molybdenum electrode bars 40 from the power supply 50. First coils 51a-l, 51a-2, •••, 51a-n of the balancing transformers 51 (51-1, 51-2, •••, 51-n) are
connected to each other in a parallel manner, while second coils 51b-l, 51b-2, •••, 51b-n of the balancing transformers 51 (51-1, 51-2, •••, 51-n) are connected to each other in a serial manner. Further, by the balancing transformers 51 (51-1, 51-2, •••, 51-n), the molybdenum electrode bars 40 can be controlled dividing them into several groups according to their positions.
Referring back to Fig. 3, the electric boosting system further includes a bubble supply device 60 which produces bubbles into the molten glass G to form a bubble barrier. The bubble supply device 60 is provided with a gas injection device 61 for supplying the gas, such as air or oxygen; and a plurality of nozzles 62, which are connected to the gas injection device 61, and which are installed along a width direction of the melter 10 in a line so as to penetrate the bottom 11 and supply the gas into the molten glass G. And the gas injection device 61 and the nozzles 62 are connected to each other by gas lines 63. The gas injection device 61 can be constituted by well known a gas compressor, a blower, an oxygen cylinder and the like. The nozzles 62 inject the gas into the molten glass G at the hot spot zone Z3, forming the bubble barrier of the molten glass G, and the convection current of the molten glass G is divided into the rear roll Gl and the front roll G2 by the bubbles.
In the electric boosting system for a melter of a glass melting furnace as described above, the glass raw
materials B are charged through the dog house 13 of the melter 10 in a state in which the melter 10 is heated to a predetermined temperature by the operation of the heating device. The charged glass raw materials B begin to be melted by a high temperature atmosphere of the melter 10 and flames emitted through the ports 18, and the molten glass G fills a space surrounded by the sidefluxes 12a and moves downstream. At this time, in the cooling zone Z3 of the melter 10, the molten glass G is cooled down by a forced air cooling method, adjusting the temperature of the molten glass G. Therefore, the convection current of the molten glass G has the rear roll Gl, the front roll G2 and the hot spring G3, wherein the rear roll Gl and the front roll G2 are separated by the hot spot zone Zl interposed therebetween.
Further, when the power is applied to the molybdenum electrode rods 40 by the operation of the power supply device 50, the molten glass G acts as a resistance heating element, so that electric resistance heat is generated therein.
The balancing transformers 51 (51-1, 51-2, •••, 51-n) controls the power from the power supply 50 in such a manner that the currents applied to the molybdenum electrode bars 40 are substantially identical. Although the electric resistance of the molten glass G is varied with its temperature, substantially identical amount of current is
supplied to each of the molybdenum electrode bars 40, so that the operation of the molybdenum electrode bars 40 can be controlled conveniently and precisely regardless of the temperature of the molten glass G.
As described above, by the operation of the molybdenum electrode bars 40, heat needed for melting the glass raw materials B can be sufficiently supplied. Further, erosion of the melter 10 and lifespan shortening of the burners due to excessive radiant heat can be prevented, the amount of fuel consumed by the burners can be reduced, thus improving the economic efficiency of the melting glass furnace.
Further, the molybdenum electrode bars 40 can be grouped into several groups whose operations are performed separately. For example, heat supply by the operation of the molybdenum electrode bars 40 can be controlled so as to produce a temperature distribution in the molten glass G along a length direction of the melter 10, in which the temperature is increased gradually as moving from a batch zone Z4, i.e., a front portion of the heating zone Zl, to the hot spot zone Zl, and the temperature is kept uniform in the downstream region from the hot spot Zl. That is, electric resistance heating rates of the molybdenum electrode bars 40 are set to be different, so that the convection current of the molten glass G including the front roll G2, the rear roll Gl and the hot spring G3 can be stabilized, thus improving efficiency of the melter 10 and
effectively preventing defects due to unstable flow and flow stagnation of the molten glass G.
As shown in Fig. 3, the gas from the gas injection device 61 of the bubble supply device 60 is delivered to the nozzles 62 through the gas lines 63, and the nozzles 62 inject the gas into the molten glass G to form the bubble barrier. The bubbles float up to the surface of the molten glass G, promoting the convection current of the molten glass G in the melter 10, which is divided into two portions by the hot spot zone Zl interposed between the two portions. That is, the rear roll Gl formed in the upstream region from the hot spot zone Zl, the front roll G2 formed in the downstream region from the hot spot zone Zl are facilitated. Therefore, the molten glass G becomes thermally, chemically and physically homogenous with more certainty.
As described above, in accordance with the electric boosting system for a melter of a glass melting furnace of the present invention, a plurality of the molybdenum electrode bars are installed in the bottom of the melter along the length direction of the melter to generate the electric resistance heat of the molten glass, so that heat needed for melting the glass raw materials can be sufficiently supplied, thus improving the efficiency of the glass melting furnace remarkably. Further, by forming the bubble barrier at the hot spot zone, flow of the molten glass can be regulated and controlled conveniently and
precisely, and the lifespans of the burners and the melter can be guaranteed, improving the economic efficiency.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed is:
1. An electric boosting system for a melter of a glass
melting furnace, the melter having a heating zone, a hot
spot zone and a cooling zone for melting glass raw materials
charged into a batch zone through a dog house to form a
molten glass, the electric boosting system comprising:
a plurality of molybdenum electrode bars, provided at the heating zone and the cooling zone, for generating electric resistance heat of the molten glass, the plurality of molybdenum electrode bars being disposed at a bottom of the melter and installed along two opposite side end portions of the bottom of the melter so as to face each other; and
a power supply connected to the molybdenum electrode bars to apply thereto a power needed for operation of the molybdenum electrode bars.
2. The electric boosting system of claim 1, further comprising a plurality of balancing transformers connected between the molybdenum electrode bars and the power supply to control currents applied to the individual molybdenum electrode bars to become substantially identical.
3. The electric boosting system of claim 1, further comprising a bubble supply device which supplies a gas into
the molten glass in the melter to form a bubble barrier of the molten glass.
4. The electric boosting system of claim 3, wherein the bubble supply device includes a number of nozzles disposed at the bottom of the melter to inject the gas into the molten glass to form the bubble barrier, and a gas injection device connected to the nozzles to supply the gas thereto.
5. The electric boosting system of claim 4, wherein the nozzles are installed at the hot spot zone along a width direction of the melter.
6. The electric boosting system of claim 3, wherein the
bubble barrier serves to regulate a flow direction of the
molten glass at the heat zone.
7. A system constructed and arranged substantially as
herein described with reference to or as shown in the
accompanying drawings.