GB2031402A

GB2031402A - A Glass Melting Furnace for Fabricating Glass Fibers

Info

Publication number: GB2031402A
Application number: GB7922212A
Authority: GB
Original assignee: Paramount Glass Manufacturing Co Ltd
Current assignee: Paramount Glass Manufacturing Co Ltd
Priority date: 1978-10-13
Filing date: 1979-06-26
Publication date: 1980-04-23
Also published as: JPS5749493B2; AU4838679A; IT7950356A0; IT1162674B; JPS5556030A; AU524094B2

Abstract

Mixed raw glasses of different melting points are melted in a glass melting furnace by at least two pairs of electrodes one pair beneath the supply port being spaced at a smaller interval than the other pair(s) and being so arranged that the adjacent electrodes of the pairs are of the same polarity. Extra heating is supplied by resistance heater groups arranged in parallel above the raw glass melt in melting and refining zones with certain heater groups detachably inserted for initial melting and withdrawn during the continuous operation. <IMAGE>

Description

SPECIFICATION A Glass Melting Furnace for Fabricating Glass Fibers This invention relates to an improved glass melting furnace and, more particularly, to an improved apparatus for fabricating glass fibers by completely melting the mixture of raw glass with other raw glass of higher melting temperature than the raw glass therein in high melting capacity with narrower hearth area of the glass melting furnace without necessity of using a combustion burner at the initial.

It is matters of common knowledge to utilize Joule heat in a glass melting furnace for fabricating glass fibers. In case where scrap glasses are used as raw glass to fabricate the glass fibers, various types of glasses might be contained in the raw glass such as, for example, so-called hard glass of approx. 1,000 poises in viscosity at 1 ,2500C., which will be hereinafter called glass of high melting point, mixed with socalled soft glass of approx. 1 ,000 poises in viscosity at 1,1 500C., which will be hereinafter called glass of low melting point.

In order to thus melt the glass of high melting in the glass of low melting point in a glass fiber fabrication, it is necessary to set the temperature of the melting site in the glass melting furnace to meet the temperature of the glass of presumed high melting point.

If the melting site of the glass melting furnace is set high at temperature as described above, it must accommodate considerably wide volume in accordance with the necessity of lowering the glass passed through melting and clarifying steps to its working temperature in the glass melting furnace. Inasmuch as it requires long cooling time if the melting point of the raw glass is particularly high, the furnace will unavoidably increase its hearth area and accordingly its floor area thereof, also from the standpoint of the need of increasing the anti-corrosion of its refrectory materials.

In addition, it is also necessary to melt the raw glass by a raw glass combustion burner at the initial operation of the glass melting furnace until it becomes conductive resulting in the necessity of accompanied facility therefor, which is unnecessary at its continuously operating time.

Accordingly, it is an object of the present invention to provide a glass melting furnace which can preferably melt raw glass mixed with other raw glass of high melting point than the raw glass together by enhancing the Joule heat due to the reduced interval among the electrodes at the raw glass supply side.

A further object of the present invention is to provide a glass melting furnace which can fabricate uniform primary glass filaments of high quality in mass production by supplying sufficient heat necessary to remove bubbles and clarify the molten glass due to the increased interval among the electrodes at the clarifying tank side.

Another object of the present invention is to provide a glass melting furnace into which raw glasses can be continuously charged by arranging a plurality of heating elements in the glass melting tank with some elements directly under the raw glass supply port being detachably inserted into the tank and by pulling out the detachable elements at the continuous operation of the furnace.

Still another object of the invention is to provide a glass melting furnace which can eliminate the combustion burner required for the conventional furnace by inserting the detachable heating elements into the glass melting tank at the initial after raw glasses are charged thereinto to heat the raw glasses until the latter becomes conductive.

Still another object of the invention is to provide a glass melting furnace which can completely prevent the electrodes arranged therein from interfering with each other among their adjacent pairs in narrow glass melting tank due to the arrangement that the adjacent electrodes are equal polarity, and which can also reduce the necessary hearth area thereof with respect to the number of the electrode pairs with an easy temperature control of the molten raw glasses via the electrode pairs.

Still another object of the invention is to provide a glass melting furnace which can improve the thermal efficiency thereof by blocking the upper wall of the glass melting tank except for the raw glass supply port, which is opened directly above the electrodes of high heating capacity at raw glass supply side to thereby charge the raw glasses over the electrodes of high heating capacity and to accumulate them over the electrodes facing in contact with high temperature exhaust gas flow from the glass melting tank through the supply port externally for sufficient preheat of the charged raw glasses.

Still another object of the invention is to provide a glass melting furnace which can improve the workability thereof and can maintain the production of uniform glass fibers of high quality by connecting the heating electrodes in preferable balance with three-phase power supply and by simply and exactly controlling the temperature of the electrodes in the same manner as a single-phase power supply together with the heating elements.

The foregoing objects and other objects as well as the characteristic features of the invention will become more apparent and more readily understandable by the following description and the appended claims when read in conjunction with the accompanying drawings.

Fig. 1 is a plan view of the glass melting furnaces of one preferred embodiment of the present invention electrically connected with threephase power supply with one furnace shown in cross section; and Fig. 2 is a side elevational view in cross section of the glass melting furnace taken along the line Il-Il in Fig. 1 with respect to the positional relationship with an apparatus for fabricating attenuated primary filaments of glass fibers.

Referring now to the drawings, and to Figs. 1 and 2 showing one preferred embodiment of the glass melting furnace constructed according to the present invention, wherein like reference numerals designate the same parts in the views, two glass melting furnaces 1 and 2 are arranged in parallel together with their working tanks 3 and 4, respectively integrally connected therebetween.

Each of the furnaces 1 and 2 is of the same construction as the other, and incorporates a raw glass melting tank 5, a molten glass clarifying tank 6, and a working tank 3.

These tanks 5, 6 and 3 are sealed with their upper walls 7, 8 and 9, respectively of the same refractory material, which is matters of common knowledge and will not be described any further, at the upper surfaces thereof.

However, a raw glass supply port 10 is opened only at the upper wall 7 of the melting tank 5 for receiving raw glasses therethrough and for exhausting high temperature gas generated at least in the melting tank 5 out of the tank 5 therethrough, as shown in Fig. 2.

In Figs. 1 and 2, two pairs of electrodes 11, 12 and 13, 14 are arranged in parallel to be inserted through either one of side walls 1 5 and 16 at either one end thereof as shown at the depth lower than the surface level L of the molten raw glasses G and accordingly under the molten raw glasses G in the melting tank 5. One pair of the electrodes 11, 12 are disposed substantially under the supply port 10 opened at the upper wall 10, and the other pair of the electrodes 13, 14 are disposed in the vicinity of the clarifying tank 6 in the melting tank 5 in such a manner that the interval 11 between the electrodes 11 and 12 is substantially narrower than the interval 12 between the electrodes 13 and 14.The difference between the intervals 11 and 12 is approx. 50 mm in the preferred embodiment of the melting furnace 5.

Electric resistance heater groups 1 7, 1 8 are arranged in parallel between the surface level L of the molten raw glasses G and the upper walls 7, 8, respectively over the molten raw glasses G in the melting and clarifying tanks 5, 6, respectively.

In the preferred embodiment shown in Fig. 2, the resistance heater groups 1 7, 1 8 are composed of a plurality of bar-like resistors 1 9 inserted through the side walls 1 5, 1 6 of the melting and clarifying tanks 5, 6 respectively so that a plurality of bar-like resistors 20 located directly under the supply port 10 are detachably inserted.

In Fig. 1, the working tanks 3, 4 of the glass melting furnaces 1, 2, respectively are integrally connected substantially in Tshape toward the longitudinal direction of the molten glasses G flow path in the clarifying tank 6 to the clarifying tanks 6, 8, respectively to be at 950 therebetween in the preferred embodiment shown.

As shown in Fig. 2, each of the working tanks 3, 4 accommodates a pair of primary glass filament spinning nozzle groups 21, 22 formed underneath the bottoms thereof. In addition, there are provided a primary glass filament 23 group separator 24, a pair of feed rollers 25, a support 26, and a combustion furnace 27 disposed sequentially under the working tanks 3, 4 as shown in Fig. 2. The glass filament 23 groups are thus introduced into hot blast 28 ejected from the combustion furnace 27 and are attenuated by the hot blast 28 to become attenuated glass fibers 29, which are carried with the hot blast 28 in the direction as designated by an arrow A and are collected by a collecting net within a suction box (not shown) and are then laminated in mat shape.

It is noted that the primary glass filaments 23 may also be wound while maintaining their long fibrous filaments.

In the preferred embodiment shown in Fig. 1, the electrodes 11 to 14 of the glass melting furnaces 1,2 and the resistance heater groups 17, 18 arranged in the furnaces 1, 2 are connected to a three-phase power supply in such a manner that the electrodes 11 to 14 are connected to the wires R and T, the heater groups 17, 1 8 are connected to the wires Rand S of the three-phase power supply, and the heater groups of the furnaces 1, 2 are connected through circuits 30, 31 to the wires S and T of the power supply. The three-phase AC power supply is balanced upon correction of the power consumption of the heater groups 1 7, 1 8 when operating both the furnaces 1, 2.

However, only a plurality of bar-like resistors 20 of the heater groups 1 7 are used merely at the initial time and are then detached from the furnace 1 during the operation of the furnace 1 as will be hereinafter described in greater detail.

In Fig. 1, the circuit 30 of the secondary winding of the transformer from the three-phase AC power supply is connected to the heater groups 17,18 of the furnace 1 , and the circuit 3 3 connected to the heater groups 1 7, 18 of the furnace 2.

As readily obvious from Fig. 1 , the adjacent electrodes 11, 1 3 of two pairs of the electrodes 11 to 14 are connected to the circuit 32 of the secondary winding of the transformer from the three-phase AC power supply in the same polarity.

The electrodes 11 to 14 are power controlled via a thyristor controller, and the heater groups 1 7, 1 8 are controlled at their temperature via a temperature controller or manual operation (not shown).

It is noted as was described before that, when scrap glasses are used as raw glass, some of the glasses have unexpectedly high melting point so that it is necessary to retain high temperature of sufficiently melt the glass of high melting point in the vicinity of the supply port 10 in the glass melting furnace 1 and also to lower such high temperature molten glass to the temperature for suitably spinning it.

In the preferred embodiment shown of the present invention, the above necessity is performed by the arrangement that the interval between the electrodes 11 and 12 in the glass melting furnace 1 or 2 is substantially narrower than that between the electrodes 13 and 14 in the clarifying tank.More particularly, in the preferred experimental embodiment, when the interval Ii between the electrodes 11 and 12 was 450 mm and the interval 12 between the electrodes 13 and 14 was 500 mm, and the molten glass temperature between the electrodes 11 and 12 was retained at 1,3000 to 1 ,3500C., the molten glass temperature between the electrodes 13 and 14 in the clarifying tank 6 could be lowered to 1 ,2500C. and the molten glass temperature could also be iowered to approx. 1,1 000C at the upper portions of the spinning nozzles 21 and 22 in the working tank 3.

Since large current flows between the electrodes 11 and 12 spaced at the interval Ii greater than that between the electrodes 13 and 14 spaced at the interval 12 to thereby raise the molten glass temperature in the melting furnace 1 and to thus maintain high molten glass temperature between the electrodes 11 and 12, raw glass of high melting point such as, for example, 1 ,2500C., though mixed with the most raw glass of low melting point such as 1,1 500C or the like, is completely molten in the molten glass of high temperature such as 1,3000 to 1 ,3500C.

The electrodes 13 and 14 spaced at the interval 12 operate to supply necessary heat to completely mix the molten glasses, remove the bubbles therein and clarify the molten glasses and to gradually cool the molten glass toward the working tank 3 at preferred working temperature in the working tank 3.

It is noted that, though the electrodes 11 and 13 are disposed adjacent to one another in the electrodes 11 to 14, they are in the same polarity with the result that no current flows between the electrode 11 and 13 but the current will flow only between the electrodes 11 and 12 and between the electrodes 13 and 14 to cause most effective Joule heat therebetween.

The above described operation refers to the case that molten glasses already exist in the melting tank 5. At the initial operation of the glass melting furnace 1 or 2 the heater groups 1 7 operate to melt the raw glasses as arranged at the upper portion of the melting tank 5. More particularly, the resistors 20 detachably inserted directly under the supply port 10 are withdrawn at the initial time, and predetermined amount of raw glasses are charged into the melting tank 5.

The resistors 20 are then inserted into the melting tank 5. All the heater groups 17, 18, and electrodes 11 to 14 are energized at the initial time. The raw glasses in the tank 5 start melting by means of radiated heat from the heater groups 1 7 to then exhibit conductive and to flow large current between the electrodes 11 and 12, and 13 and 14 to thereby completely melt and mix the raw glasses. Then, the resistors 20 are withdrawn from the tank 5 directly under the supply port 10.

Raw glasses are then continuously supplied from the port 10 to thereby continuously spin the molten glasses to primary glass filaments 23 from the spinning nozzles 21 and 22 in the working tank 3.

The electrodes 11 to 14 mainly melt the raw glasses during this continuous operation, and the heater groups 1 7, 1 8 auxiliarily heat to maintain the molten glass temperature.

In Fig. 2, raw glasses charged through the supply port 10 are accumulated on the upper surface of the molten glass G at the position of the electrodes 11 and 12 during the continuous melting operation of the raw glasses as described above. Molten glass of the level L is exposed at the position of the electrodes 13 and 14. High temperature exhaust gas flow dispatched from the molten glasses at this position is exhausted out of the tank 5 through the supply port 10 while contacting with the surfaces of the raw glasses accumulated on the surface of the molten glass G at the position of the electrodes 11 and 12 as described above to thereby thermally exchange the heat of the exhaust gas with the surfaces of the raw glasses accumulated thereat so as to preheat the accumulated raw glasses.

In the experimental embodiment of the present invention, the melting tank had 1;5 m long and 0.6 m wide with floor area of 0.9 m2 performed glass melting capacity of 3,600 kg/m3 of glass wool for 24 hours. This performance corresponds to 4,000 kg/m3 of glass wool per unit furnace floor area for 24 hours.

In the meantime, the most superior conventional glass melting furnace of 1.4 m long and 1.0 m wide in the melting tank with floor area of 1.4 m2 carried out glass melting capacity of 1,575 kg/m3 of glass wool for 24 hours from general reference. This performance corresponds to 1,125 kg/m3 of glass wool per unit furnace floor area for 24 hours. From these results, the glass melting furnace of the present invention can perform approx. 3.5 times the conventional most superior glass melting furnace.

It should be understood from the foregoing description that since the glass melting furnace of the present invention exhibits high Joule heat due to the reduced interval among the electrodes at the raw glass supply side, it can preferably melt, raw glass mixed with other raw glass of higher melting point than the raw glass together. It should also be understood that since the glass melting furnace of the present invention has longer interval between the electrodes in the clarifying tank than that between the electrodes in the melting tank to supply sufficient heat necessary to remove the bubbles and to clarify the molten glass, it can fabricate uniform primary glass filaments of high quality in mass production and that since the present invention arranges a plurality of heating elements or resistance heaters in the glass melting tank with some heaters directly under the supply port being detachably inserted into the tank to pull out the detachable heaters during the continuous operation after the' initial time, it can continuously receive the raw glass from the supply port.

It should also be appreciated that, since the glass melting furnace of the present invention can insert the detachable heaters into the glass melting tank at the initial time after raw glasses are charged into the tank to thereby heat the raw glasses therein until the latter becomes conductive, it can eliminate the conventional combustion burner required at the initial operation and that since the melting furnace of the present invention incorporates the adjacent electrodes of equal polarity of the electrodes in the melting tank, it can completely prevent the adjacent electrodes from interfering with each other so as to thereby reduce the necessary hearth area thereof with respect to the number of the electrodes with an easy temperature control of the molten raw glasses via the electrode pairs.

It should also be understood that since the melting furnace of the present invention blocks all the upper walls of the glass melting tank, clarifying tank and working tank except for the raw glass supply port, which is opened directly above the electrodes of high heating capacity at the raw glass supply side to thereby charge the raw glasses over the electrodes of high heating capacity and to accumulate them over the electrodes facing in contact with high temperature exhaust gas flow from the glass melting tank through the port externally, it can improve the thermal efficiency thereof and sufficiently preheat the charged raw glasses accumulated over the electrodes.

It should also be appreciated that since the melting furnace of the invention connects the heating electrodes in preferable balance among the three-phase power supply and can simply and exactly control the temperature of the electrodes in the same manner as a single-phase power supply with the heaters, it can improve the workability thereof to maintain the production of uniform glass fibers of high quality.

Claims

1. A glass melting furnace for fabricating glass comprising: at least two pairs of electrodes arranged in parallel at depth lower than the level of molten raw glass in a glass melting tank, one pair of said electrodes disposed substantially under raw glass supply port opened thereover and the other of said electrodes disposed in the vicinity of a clarifying tank adjacent to the glass melting tank in such a manner that the interval between the first pair of the electrodes is substantially narrower than that.between the second pair of the electrodes and that the adjacent electrodes thereof is in the same polarity, and a plurality of resistance heater groups inserted through the side walls of the melting and clarifying tanks, respectively in parallel between the surface level of the molten raw glass and the upper walls over the molten raw glass in the melting and clarifying tanks so that predetermined number of said heater groups located directly under the supply port are detachably inserted.

2. The glass melting furnace according to claim 1, wherein the difference between the intervals between the first and second pairs of the electrodes is substantially 50 mm.

3. The glass melting furnace according to claim 1, wherein the raw glass supply port is opened at the upper wall of the glass melting tank over the first pair of the electrodes for supplying the raw glasses, and all the upper walls except for the supply port are blocked.

4. A glass melting furnace for fabricating glass fibers comprising: at least two glass melting furnace means each having: at least two pairs of electrodes arranged in parallel at depth lower than the level of molten raw glass in a glass melting tank, one pair of said electrodes disposed substantially under raw glass supply port opened thereover and the other of said electrodes disposed in the vicinity of a clarifying tank adjacent to the glass melting tank in such a manner that the interval between the first pair of the electrodes is substantially narrower than that between the second pair of the electrodes and that the adjacent electrodes thereof is in the same polarity, and a plurality of resistance heater groups inserted through the side walls of the melting and clarifying tanks, respectively in parallel between the surface level of the molten raw glass and the upper walls over the molten raw glass in the melting and clarifying tanks so that predetermined number of said heater groups located directly under the supply port are detachably inserted, and a three-phase AC power supply electrically connected through two of respective three wires to the electrodes of one and the other glass melting furnace means and to the resistance heaters of both the glass melting furnace means.

5. The glass melting furnace according to claim 4, wherein the working tanks of said glass melting furnaces are integrally connected substantially in Tshape toward the longitudinal direction of the molten glass flow path in the clarifying tank to the clarifying tanks at substantially 95 therebetween.

6. The glass melting furnace according to claim 1, wherein large current flows between the first pairs of the electrodes spaced at the interval greater than that between the second pairs of the electrodes spaced at the interval to thereby raise the molten glass temperature in the melting furnace and to thus maintain high molten glass temperature between the first pairs of the electrodes.

7. The glass melting furnace according to claim 1, wherein the second pairs of the electrodes spaced at the interval greater than that of the first pairs of the electrodes supply only heat necessary to completely mix the molten glasses, remove the bubbles therein and clarify the molten glasses and to gradually cool the molten glass toward the working tank.

8. The glass melting furnace according to claim 1, wherein said resistance heater groups are composed of a plurality of bar-like resistors inserted through the side walls of the melting and refining zones, respectively to that a plurality of bar-like resistors located directly under the supply port are detachably inserted.

8. The glass melting furnace according to claim 1, wherein said resistance heater groups are composed of a plurality of bar-like resistors inserted through the side walls of the melting and clarifying tanks, respectively so that a plurality of bar-like resistors located directly under the supply port are detachably inserted.

9. A glass melting furnace substantially as described herein with reference to the accompanying drawings.

New Claims or Amendments to Claims filed on 11 Jan. 1980.

Superseded Claims 1, 4, 5, 7, 8.

New or Amended Claims:

1. A glass melting furnace for fabricating glass fibers comprising: at least two pairs of electrodes arranged in parallel at depth lower than the level of molten raw glass in a glass melting tank, one pair of said electrodes disposed substantially under raw glass supply port opened thereover and the other of said electrodes disposed in the vicinity of a refining zone adjacent to the glass melting tank in such a manner that the interval between the first pair of the electrodes is substantially narrower than that between the second pair of the electrodes and that the adjacent electrodes thereof is in the same polarity, and a plurality of resistance heater groups inserted through the side walls of the melting and refining zones, respectively in parallel between the surface level of the molten raw glass and the upper walls over the molten raw glass in the melting tank and refining zone so that predetermined number of said heater groups located directly under the supply port are detachably inserted.

4. A glass melting furnace for fabricating glass fibers comprising: at least two glass melting furnace means each having: at least two pairs of electrodes arranged in parallel at depth lower than the level of molten raw glass in a glass melting tank, one pair of said electrodes disposed substantially under raw glass supply port opened thereover and the other of said electrodes disposed in the vicinity of a refining zone adjacent to the glass melting tank in such a manner that the interval between the first pair of the electrodes is substantially narrower than that between the second pair of the electrodes and that the adjacent electrodes thereof is in the same polarity, and a plurality of resistance heater groups inserted through the side walls of the melting tank and refining zone, respectively in paralled between the surface level of the molten raw glass and the upper walls over the molten raw glass in the melting tank and refining zone so that predetermined number of said heater groups located directly under the supply port are detachably inserted, and a three-phase AC power supply electrically connected through two of respective three wires to the electrodes of one and the other glass melting furnace means and to the resistance heaters of both the glass melting furnace means.

5. The glass melting furnace according to claim 4, wherein the working ends of said glass melting furnaces are integrally connected substantially in T shape toward the longitudinal direction of the molten glass flow path in the refining zone to the working ends at substantially 950 therebetween.

7. The glass melting furnace according to claim 1, wherein the second pairs of the electrodes spaced at the interval greater than that of the first pairs of the electrodes supply only heat necessary to completely mix the molten glasses, remove the bubbles therein and refine the molten glasses and to gradually cool the molten glass towards the working end.