JPH0139971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric melting furnace that applies electricity directly to the molten glass itself, melts a batch of raw glass by the heat of the molten glass, and homogenizes and clears the molten glass. It relates to such an electric melting furnace that spins directly into glass fibers without going through risers and feeders.

Glass products, such as glass fibers, are produced industrially by melting and clarifying powdered raw material glass batches with flame in an open hearth melting furnace made of a refractory material, and guiding the molten glass through a channel to a forehearth made of a refractory material. It is produced by spinning from a plurality of platinum bushings arranged at the bottom of the formation while conditioning and controlling the temperature by resistive heat generation by energization of the platinum material that makes up the platinum material (for example, ,
(See Special Publication No. 39-5219 and Publication No. 46-34941).

In contrast to such a melting, fining, and forming system consisting of an open hearth melting furnace and a steel melting furnace, a vertical electric melting furnace has recently been developed. In this vertical electric melting furnace, the electrodes are appropriately placed relatively at the upper part of the furnace, and when electricity is applied directly to the molten glass in the furnace, an appropriate vertical temperature distribution is generated in the molten glass, and at the same time, the electrodes are placed in the upper part of the furnace. The relatively high temperature, low density molten glass is difficult to mix into the relatively low temperature, high density molten glass region below, even against the force of gravity. The heating convection area is
On the other hand, it is based on the simple principle that a laminar clear region of molten glass is formed relatively below. In this way, the electric melting furnace naturally and functionally achieves melting, stirring, and diffusion of glass batches in the same furnace, and achieves homogeneous melting near the bottom of the furnace.
It has a clear melting theory and a simple process that are not found in conventional open hearth systems that produce clarified molten glass, and thus achieves miniaturization of equipment and improved thermal efficiency. The use of electrical energy used to be expensive compared to fossil fuels even when efficiency was taken into account, but the simplicity and high efficiency of the process in electric melting furnaces, combined with the recent rise in the price of fossil fuels, has given rise to its advantages. It is gradually improving its properties and establishing itself as a new glass melting technology.

As such an electric melting furnace, for example,
Publication No. 26884 generates thermal energy by energizing the molten glass at at least two levels in at least one melting zone in the upper part of a melting tank, such that the levels are opposite in direction. An electric melting furnace and method is disclosed having a three-phase AC electrode arrangement that creates and maintains a circulating flow of molten glass.

In addition, Japanese Patent Application Laid-Open No. 47-13618 discloses that in a glass electric melting furnace having electrode groups on multiple planes in the furnace, the inner end of the electrode group on one plane is connected between the ends of the electrode groups on the plane above and below. an electric melting furnace located in the gap, thus causing the ascending glass stream of each lower plane to meet the descending glass stream of each upper plane at the interface with the upper plane, and preventing each glass stream from penetrating into the other plane; and a melting method.

Furthermore, Japanese Patent Publication No. 56-9455 discloses a method for minimizing convection of unmelted glass batches or incompletely melted glass batches deposited on molten glass in an electric melting furnace toward the furnace wall near the electrodes. , above an electrode that is immersed in molten glass,
Moreover, an electric melting furnace is disclosed in which a batch baffle plate means is attached to the furnace wall at a position where it does not come into contact with the molten glass.

Conventional electric melting furnaces, including these publications, have in common that their horizontal cross-sectional shape is a regular 3n square with n = 2 or more, usually a hexagon to a dodecagon, and typically a hexagon. . For example, the above-mentioned special public service
No. 26884 discloses a furnace structure consisting of a hexagonal upper vertical part and an inverted hexagonal pyramidal funnel-shaped bottom part connected thereto, and also discloses a furnace structure consisting of a hexagonal upper vertical part and an inverted hexagonal pyramidal funnel-shaped bottom part, and
56-9455 both disclose hexagonal prism structures.

Glass melting furnaces require temperatures of over 1,000 degrees to melt glass batches, so they are constructed of refractory materials such as refractory bricks that can withstand such temperatures. Corrosion caused by glass cannot be avoided, and its service life is only 2 to 3 years.
It is said to be around 20 years old. At the end of their useful life, furnaces are refurbished or newly built, and the cost of the furnace represents a significant portion of the cost of producing glass products. On the other hand, corrosion of fireproof materials by molten glass is not a practical problem in the early stages of operation;
The safe operation of the furnace becomes a major problem as it approaches the latter stages of operation. Therefore, the simplicity of the furnace form and the stability of the furnace structure not only guarantee the ease of furnace construction, support and reinforcement work for the furnace, but also increase the durability of the furnace and ensure the operational safety of the furnace. It is also an important factor in the sense that When considering conventional electric melting furnaces from these viewpoints, the polygonal shape increases the technical difficulty of furnace construction, makes external support and reinforcement work complicated and difficult, and makes it difficult to use refractory materials based on the polygonal shape. The large number of joints between the two leads to an increase in the number of eroded areas where erosion by molten glass progresses more vigorously, and this, together with the fact that the depth of the furnace is several times that of an open hearth, impedes the overall structural stability of the furnace. This is a contributing factor.

Another feature common to conventional electric melting furnaces is that the melting furnace is connected to a riser or other flow passage through a passage such as a throat, and is connected to a sequential forming device or further through a feeder. It is used by being connected to a molding device.
For example, in the above-mentioned Japanese Patent Publication No. 52-26884, molten glass is passed through a flow path connected to a stoppered opening provided in the side wall of a funnel-shaped bottom so as to form a free surface in contact with the surrounding air. JP-A No. 47-13618 teaches that the molten glass is sent to a molding machine while being dipped, and the inlet and outlet of the furnace bottom are connected to an upright glass passage (riser) with a throat, and the molten glass is It is disclosed that the material is sent from this riser to a feeder passage or feeder, temperature controlled, and taken out for molding.

This arrangement is used to refine the molten glass to be molded into the final product according to the molding conditions of each product, or to condition it to adjust the temperature and viscosity conditions, as well as to adjust the glass level related to molding pressure. However, on the other hand, such an arrangement inherently includes the following problems or contradictions.

That is, the need for additional equipment such as risers and feeders, and for refining and/or conditioning of these equipment, inevitably results in increased costs in terms of equipment and energy. This cost increase becomes more significant when the scale of production is relatively small.

In addition, in an electric melting furnace, when the homogenized and clarified glass comes into contact with the refractory material of the riser and feeder, contamination due to elution of the refractory material and glass components such as B ₂ O ₃ or There is also the problem of additional heterogeneity caused by evaporation of alkali metal oxides.

By the way, during the melting process of raw glass batches, as is well known, an equilibrium relationship between gas and liquid is established in the molten glass, and dissolved gas is present in the molten glass. Therefore, if the temperature is constant, changes in pressure will have a significant effect on the generation and disappearance of bubbles in the molten glass. On the other hand, in a typical vertical furnace, the molten glass generally has a depth of about 1.5 to 3 m, and a pressure difference of about 0.38 to 0.75 Kg/cm ² exists between the surface and the bottom. This is sufficient pressure to influence the generation and disappearance of the bubbles. Thus,
Lifting the molten glass through a flow path or through a riser while forming a free surface between it and the surrounding air means releasing the pressure on the glass and reintroducing bubbles into the molten glass that has been refined. This inherently has the paradox of bringing about the state in which it occurs.

In the production of glass fiber, the present inventor has discovered that when properly controlling the laminar flow fining conditions in a vertical electric melting furnace, the pressure of the molten glass can be released without passing the molten glass through a riser or feeder. It is possible to spin fibers directly from an electric melting furnace without any problems, and when viewed as a glass fiber forming method, it provides processing that cannot be achieved with the conventional electric melting furnace-feeder system or the conventional open hearth system. The present invention has been completed by discovering that pressure forming can be achieved without the need for any additional means.

Thus, an object of the present invention is to provide a vertical electric glass melting furnace having a glass fiber spinning device directly on the bottom of the furnace, which can form glass fibers without passing through a throat, riser, or feeder. do.

Another object of the present invention is to enable an advantageous arrangement of glass fiber spinning equipment and to provide a highly structurally stable spinning device.
An object of the present invention is to provide a vertical electric glass melting furnace having a glass fiber spinning device directly on the bottom of the furnace.

According to the invention, basically a melting convection zone for raw glass batches having a receiving opening for the raw glass batches at the top; and a vertical opening for taking out a plurality of molten glasses at the bottom and for said melting convection zone. a laminar flow clarification zone of molten glass which is connected vertically downwardly and in which the head of the molten glass of said molten convection zone is in a direct acting relationship; , a group of electrodes for directly energizing the molten glass, penetrating and disposed on the peripheral wall defining the zone; disposed directly on the exit side in communication with the vertical opening of the laminar flow clarification zone; a plurality of glass fiber spinning devices, wherein the pressurized molten glass at the bottom of the laminar flow clarification zone is directly fed to said spinning device without releasing its pressure, and the glass fibers are An electric melting furnace is provided for spinning.

According to the electric melting furnace of the present invention, the molten glass that has been melted, homogenized, and clarified in the melting furnace is supplied directly to the spinning device connected to the bottom opening of the furnace without passing through the riser and feeder, Thus, the technical and economical problems and contradictions of the conventional electric melting furnace spinning can be solved, and the pressurized molten glass in the melting furnace can be directly supplied to the spinning device. achieves pressure forming without the need for any pressure means. This pressure spinning of glass fibers is carried out by orifices installed in the orifice plate or nozzle plate of the spinning device, which significantly improves the outflow of the molten glass through the tip nozzle and the separation characteristics of the molten glass cone formed at the outlet of the orifice or tip nozzle. , thus making it possible to make the orifice or tip nozzle closer together, thereby making it possible to make the spinning device more compact, and furthermore to make it possible to make the electric melting furnace itself more compact and highly efficient. Since the spinning device can be downsized, a plurality of spinning devices can be attached to the bottom of the electric melting furnace to improve productivity.

As a particularly preferred embodiment of the present invention, in the electric melting furnace for direct glass fiber spinning of the present invention,
The present invention provides an electric melting furnace for direct spinning of glass fibers, characterized in that the horizontal cross-sectional shapes of the melting convection zone and the laminar flow clarification zone are rectangular.

According to this preferred embodiment, an economical arrangement of a plurality of spinning devices in the electric melting furnace and an effective arrangement to facilitate the spinning operation are possible, and the rectangular cross-sectional structure facilitates the construction of the furnace and its support and reinforcement work. This also reduces joints between refractory materials where erosion by molten glass is more severe, thus significantly improving the overall structural stability of the furnace. In addition, suitable natural heat dissipation for good conditioning of the molten glass in the furnace is achieved.

The present invention described above will be further explained with reference to the accompanying drawings. However, the illustrated electric melting furnace is a preferred embodiment of the present invention, and the present invention is of course not limited thereto.

In the accompanying drawings, FIGS. 1 and 2 relate to a relatively small-sized electric melting furnace according to the present invention, and FIG. 1 shows a front longitudinal sectional view thereof, and FIG. Figures are shown respectively.

1 and 2, an electric melting furnace 1 is defined by a peripheral wall 2 made of refractory bricks and a furnace bottom wall 3, the relative upper part of which constitutes a melting convection area 4 for molten glass. , the relatively lower part constitutes a laminar flow clarification zone 5 of the molten glass.

The top of the melting convection zone 4 is fully open to receive the raw glass batches and to form a deposited layer 7 of glass batches on top of the furnace molten glass 6. Although not shown, a feeding device for raw glass batches is disposed above the top opening, and the glass batches are continuously or intermittently supplied to the opening, preferably by scattering. . In this melting convection zone 4, the glass batch is melted and a certain degree of clarification and homogenization takes place under thermal convection.

On the other hand, the laminar flow clarification zone 5 is directly connected vertically downward from the melt convection zone 4 and is closed by the furnace bottom wall 3. In this laminar flow clarification zone 5, the molten glass continuously fed from the melt convection zone 4 is substantially completely homogenized and clarified.

The cross-sectional area of the melting convection zone 4 and thus of the laminar clarification zone 5 and the depth of both zones primarily depend on the throughput of the glass and are relative and vary depending on the throughput. However, at least in the melting convection zone 4, a sufficiently wide contact surface is provided between the molten glass 6 and the deposited layer 7 of glass batches to melt a sufficient amount of glass batches, and the thermal convection of the molten glass is sufficient. , but the convection is in the laminar clear zone 5
In the laminar flow fining zone, the process of homogenization and clarification involves direct shaping of the molten glass while maintaining a laminar flow state. Achieve the homogeneity and clearness of the molten glass necessary to
At the same time, the temperature and viscosity conditions required for molding are satisfied.
It must ensure sufficient residence time and heat dissipation.

At least one, but generally a plurality of vertical openings 8 are formed in the bottom wall 3, each of which is directly fitted with a bushing 9 for spinning glass fibers. The total amount of molten glass spun by these bushings should be such that it does not disturb the laminar flow state of the molten glass in the laminar flow clarification zone. The bushing 9 can be the same as in the case of the open hearth type, and its attachment can also be performed by applying the means of the open hearth type.

The vertical opening 8 is provided with a molten glass guide part 10 that surrounds the entrance and protrudes from the bottom of the furnace into the furnace, and prevents the molten glass from flowing down along the peripheral wall of the furnace, which is contaminated with leached refractory materials, etc. is a direct opening 8
It is preferable to prevent it from flowing into the bushing 9 from the outside. The guide part 10 can be made of a corrosion-resistant, refractory material, but it can also be formed by other means, for example by extending a platinum alloy plate constituting the bushing wall and projecting it into the furnace through the opening 8. Further, the platinum alloy plate constituting the bushing can be extended and covered with the guide portion 10 made of the above-mentioned corrosion-resistant and fire-resistant material. On the other hand, deposits such as contaminated glass and eluted refractory materials can be successively removed from a drain port 11 formed approximately in the center of the furnace bottom 3.

The illustrated electric melting furnace 1 shows a melting furnace with a rectangular cross-sectional structure. In this rectangular furnace, its cross-sectional shape can be rectangular or square. When taking a rectangular cross-sectional shape, the ratio of the length of the short side to the long side can vary considerably, for example, the short side is 1/3 of the long side.
Or it can be less than that. This is because the electrical conductivity of molten glass to which electricity is applied varies considerably depending on the glass composition. Such a rectangular cross-sectional structure is advantageous from the viewpoint of good conditioning of the molten glass based on heat dissipation, ease of furnace construction, support and reinforcement, improvement of the structural stability of the furnace, and also from the viewpoint of the arrangement of spinning equipment. Although this is recommended as a particularly preferred embodiment, the present invention does not exclude the adoption of the conventional regular 3n polygonal structure where n=2 or more.

In the electric melting furnace 1 of the present invention, the number 12 represents a main electrode group, which is disposed in the melting convection area 4 at a position where it is immersed in the molten glass. Electricity is applied directly to the molten glass in the furnace through the main electrode group 12, and the generated Joule heat sequentially melts and vitrifies the glass batches in the glass batch layer 7 on the molten glass at the contact interface with the molten glass, and heats the molten glass. cause convection. As is well known, by properly arranging these electrode groups 12, a convection region is formed in the molten glass in the furnace in the upper part of the furnace, and a laminar flow region is formed in the lower part of the furnace. These two regions correspond respectively to the melt convection zone 4 and the laminar flow clarification zone 5 of the electric melting furnace 1. An auxiliary electrode group 13 can be arranged in the laminar flow fining zone 5 to aid in starting the furnace and for temperature compensation of the molten glass entering the bushing 9. These auxiliary electrode groups 13 should be controlled so as not to cause new thermal convection in the molten glass. This auxiliary electrode group 13 is not necessarily necessary and can be omitted if desired.

These electrode groups 12 and 13 are penetrated and arranged in the circumferential wall 3 in at least one horizontal level in accordance with conventional methods, but in particular in the case of rectangular furnaces it is not necessary to arrange them on the entire circumferential wall; It may also be provided only on the surrounding wall. The electric melting furnaces shown in FIGS. 1 and 2 are examples in which electrodes are arranged on the opposing short side peripheral walls. When the electrodes are disposed on the opposing walls in this manner, it is preferable that the electrodes be disposed line-symmetrically. The electrode may be either a rod-shaped electrode or a plate-shaped electrode. Although it is normal and preferable to use a three-phase power source having R, S, and T phases, it is particularly preferable to use a single-phase power source in the case of a small rectangular furnace.

3 and 4 are electric melting furnaces similar to those shown in FIGS. 1 and 2, but regarding the electric melting furnace in which the electrodes are arranged on the opposing long side peripheral walls, The figure shows a front longitudinal cross-sectional view thereof, and FIG. 4 shows a cross-sectional view taken along the plane shown in FIG. Also, Figures 5 and 6 have the same electrode arrangement as Figures 3 and 4, but relate to a medium-sized electric melting furnace that uses a three-phase power source with R, S, and T phases. , FIG. 5 shows a front vertical cross-sectional view thereof, and FIG. 6 shows a cross-sectional view taken along the - plane of FIG. In these Figures 3 to 6, reference numerals have the same meanings as in Figures 1 to 2 above.

In the electric melting furnace of the present invention, raw glass batches are dispersed and supplied to the open top of the furnace, and are deposited on the molten glass 6 in the furnace to form a batch layer 7. This batch layer 7 blocks heat radiation from the molten glass in the furnace. The glass batches of the layer 7 are successively heated at the contact surface with the molten glass by direct current flow from the electrode 12, and are gradually melted and vitrified by the high temperature heat. Most of the decomposition gas generated by the vitrification reaction at this time escapes through the batch layer and dissipates into the atmosphere.

The crude molten glass produced by vitrification is entrained and circulated in a vigorous circulating flow A of molten glass present in the molten glass in the melting convection zone 4. This circulating flow A is a thermal convection of the molten glass caused by heating by the electrodes 12. Through this convection and circulation, the heterogeneous portion of the glass is stretched, and homogeneous mixing progresses through physical mixing and diffusion, and residual gas that has not been degassed near the batch layer rises to the surface during this circulation and is degassed. be done.

The glass melted and mixed in this melting convection zone 4 is clarified to a considerable extent;
However, there are still some bubbles, non-uniform striae, and temperature unevenness, and it is still in an unfinished state. The unfinished glass then passes successively into the laminar flow fining zone 5, during which time it reaches the bottom of the furnace, where perfect homogeneity, temperature-viscosity conditions necessary for fining and spinning are achieved.

That is, in the molten glass in the laminar flow clarification zone 5, there is only a very slow downward laminar flow B based on the amount of glass drawn out for spinning, which is sufficiently small for a large amount of molten glass. There is. The molten glass from the molten convection zone 4 rides this laminar flow B and stays in the laminar flow clarification zone 5 for a long time, and while moving downward, it undergoes diffusion, auxiliary temperature control, and natural flow from the furnace wall based on heat conduction. Heat dissipation eliminates inhomogeneous areas and temperature unevenness, and at the same time, a natural temperature drop occurs, achieving the temperature-viscosity conditions necessary for spinning. In addition, among the small bubbles remaining in the molten glass from the melting convection zone 4, the lamp equation V = g・d ² ρ/12η (where, V is the flow velocity of the laminar flow C, and g is the gravity is the acceleration, d is the diameter of the bubble, ρ is the density of the molten glass, and η is the viscosity of the molten glass). On the other hand, smaller bubbles are subjected to increasing pressure as the glass moves downward, and most of them dissolve into the glass according to the law of gas-liquid equilibrium. In fact, it has been found that there are virtually no air bubbles in the molten glass at the bottom of the furnace. Thus,
Near the bottom of the furnace, there is a chemically and thermally uniform
There is a bubble-free, substantially completely homogeneous, clarified, pressurized molten glass. This pressurized molten glass has a pressure equivalent to the liquid depth of the molten glass in the furnace, but when adopting the size of a vertical furnace commonly used in industry, the pressure is approximately 0.4
~0.8Kg/ ^cm2 .

According to the present invention, this pressurized molten glass is directly spun into glass fibers by a spinning device attached to the bottom of the furnace, but the pressure is applied to the orifice or tip nozzle in the orifice plate of the bushing or the tip nozzle plate. Significantly improves and enhances the outflow of the molten glass through the orifice or tip nozzle, as well as the separation properties of the molten glass cone formed at the outlet of the orifice or tip nozzle, i.e., the molten glass flowing out of the orifice or tip nozzle does not overflow by wetting the plate material. significantly improves the properties of forming independent cones and facilitates the formation of glass fibers. This improvement in the separation properties of the cone also allows for closer or denser orifices or tip nozzles.

Next, an example of direct spinning of glass fiber using the vertical electric melting furnace of the present invention will be shown by way of example. However, it goes without saying that the present invention is not limited to this example.

Example: There are two pairs of molybdenum rod electrodes with a diameter of 50 mm that are connected to a single-phase power source above the furnace wall on the opposite short sides, and are connected to a single-phase power source through a vertical opening in the bottom of the furnace.
The base is 1600 mm long and 600 mm wide, with a drain port located approximately in the center of the hearth bottom, and equipped with 800 hole bushings.
melting, homogenizing and clarifying batches of C-glass with an alkali metal oxide content of 7.5% by weight using an electric melting furnace made of refractory bricks with a diameter of 1.5 mm and a depth of 1500 mm;
Then, pressure spinning was performed directly from the bushing. Glass fibers could be produced very well by this pressure spinning. The furnace conditions and spinning conditions are as follows.

Furnace temperature: 1410℃ in the center of the melting convection area Center of laminar clear zone 1320℃ Bushing introduction part 1270℃ Energy used: 1.45KWH/Kg - Glass Spinning conditions: Bushing temperature 1200℃ Winding speed 2000m/min Fiber diameter 14μ Production volume 20 tons/day

[Brief explanation of drawings]

FIG. 1 shows an electric melting machine having a rectangular cross-sectional structure according to the present invention, which has electrodes disposed line-symmetrically on the opposite short sides of the furnace wall and a bushing for spinning glass fibers at the bottom of the furnace. A front longitudinal sectional view of the furnace is shown, FIG. 2 is a cross sectional view taken along the plane shown in FIG. 1, and FIG. is a front longitudinal cross-sectional view of an electric melting furnace for glass fiber spinning arranged line-symmetrically on the furnace wall on the long side of the furnace, and FIG. Figure 5 shows a medium-sized electric melting furnace for glass fiber spinning, which has a rectangular cross-sectional structure similar to the electric melting furnace shown in Figure 1, but the electrodes are arranged line-symmetrically on the furnace wall on the long sides of the furnace. A front longitudinal cross-sectional view is shown, and FIG. 6 is a cross-sectional view taken along the - plane of FIG. 1... Electric melting furnace, 2... Peripheral wall, 3... Furnace bottom wall, 4... Melting convection area, 5... Laminar flow clarification area,
6... Molten glass, 7... Glass batch deposited layer,
8... Vertical opening, 9... Bushing, 10... Molten glass guide, 11... Drain port, 12...
Main electrode, 13... Auxiliary electrode, A... Circulating flow of molten glass, B... Drawing flow of molten glass, 14... Glass fiber.

Claims (1)

[Scope of Claims] 1. A melting convection area for raw glass batches having a receiving opening for the raw glass batches at the top; having vertical openings for taking out a plurality of molten glasses at the bottom and vertically downward with respect to the melting convection area; a laminar flow fining zone of molten glass in direct contact with the molten glass head of said molten convection zone; a group of electrodes for directly energizing the molten glass, which are penetrated and arranged in the defining peripheral wall; a plurality of electrodes which communicate with the vertical opening of the laminar flow clarification zone and are arranged directly on the exit side thereof; a spinning device for glass fibers, wherein the pressurized molten glass at the bottom of the laminar flow clarification zone is directly fed to said spinning device without releasing its pressure to spin glass fibers. Electric melting furnace for. 2. The electric melting furnace according to claim 1, wherein the cross-sectional shape of the furnace is rectangular. 3. The electric melting furnace according to claim 2, wherein the electrode groups are disposed line-symmetrically on a pair of opposing peripheral walls of the furnace. 4. Claim 1, wherein a molten glass guide part is formed in the vertical opening formed in the furnace bottom, surrounding the inlet and protruding from the furnace bottom toward the inside of the furnace.
The electric melting furnace according to item 1, 2 or 3. 5. The electric melting furnace according to any one of claims 1 to 4, wherein a drain port for drawing out contaminated glass is formed approximately at the center of the furnace bottom.