JPH0859250A - Glass melting furnace - Google Patents

Abstract

PURPOSE: To provide a glass melting furnace, improved in heat transmission efficiency from heating elements to a melting tank and capable of readily carrying out the exchange of the heating elements. CONSTITUTION: This glass melting furnace is equipped with a raw material charging port in the upper part, a takeout port 8 for a molten glass in the lower part and further electrical resistance heating elements 6 as a heating mechanism for melting the glass. The glass melting furnace is further provided with a cover layer 2, laminated and formed so as to cover the inner wall of the melting tank 1 and an extendedly installed discharge nozzle 9 having a riser part in the takeout port 8. Cavities are bored among the bottom wall 3 and/or a sidewall 4 and the electrical resistance heating elements 6 in the thickness direction of the bottom wall 3 and/or the sidewall 4.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a glass melting furnace.

[0002]

2. Description of the Related Art Conventionally, a continuous glass melting furnace (so-called cold top melting furnace) for melting glass in a state where the upper surface of a melting tank is covered with a batch material of glass has been widely used. Comparing this melting furnace with the tank furnace of the upper heating method, the heat radiation from the surface of the molten glass is small, so the thermal efficiency is high.The amount of volatile components volatilized to melt the glass while covering the surface of the molten glass with cold batch raw material. It has the advantages that it can be suppressed and that the structure of the melting furnace is simple. It is also suitable for relatively small volume production.

FIG. 8 shows a conventional cold top melting furnace.
The structure shown in is known. That is, a structure in which the electric resistance heating element 6 is embedded in the bottom wall 3 and the side wall 4 of the melting tank 1 and the inner wall of the melting tank 1 is covered with a cover layer 2 made of a noble metal such as platinum / platinum alloy or a heat-resistant metal such as molybdenum. Is.

In the glass melting furnace shown in FIG. 1, the batch raw material B is supplied to the entire surface of the melting tank 1 by a charging mechanism (not shown).
The batch raw material B is melted while covering the entire surface of the molten glass A. The refractory 5 forming the bottom wall 3 and the side wall 4 of the melting tank 1 is provided with a buried hole 7 for installing an electric resistance heating element 6. The buried hole 7 penetrates the refractory 5 in the horizontal direction, and the size of the buried hole 7 is large enough to insert and remove the electric resistance heating element 6.

When the electric resistance heating element 6 is deteriorated due to long-term use, the wire (not shown) connected to the end of the electric resistance heating element 6 is removed, and the electric resistance heating element 6 is inserted from the buried hole 7. And a new electric resistance heating element 6 is buried in the hole 7
It is replaced by inserting it in and connecting the ends.

[0006]

In the above conventional heating method, since the electric resistance heating element is embedded in the refractory of the melting tank, the heat transfer from the heating element to the molten glass is higher than that in the energization method using electrodes. The thermal efficiency is poor and it is difficult for the temperature in the melting tank to rise.

The temperature in the glass melting furnace is the temperature of the heating element,
The temperature difference between the heating element and the temperature of the molten glass in the melting furnace is usually about 500 to 700 ° C, although it varies depending on the installation interval of the heating element, the size of the melting furnace, the material of the refractory, the composition of the glass to be melted, etc.
Is.

Therefore, the melting temperature rises only up to about 1000 ° C., and high temperature melting cannot be performed. Therefore, there is a problem that the types of glass that can be melted are limited in the above temperature range.

On the other hand, since the temperature of the heating element becomes much higher than the temperature of the molten glass, it is necessary to select an expensive material that can withstand high temperatures as the heating element. In addition, since it is used in a high temperature state, there is a problem that the frequency of replacement increases due to deterioration of the heating element, resulting in high cost. Further, since the heating element becomes high in temperature, the heat radiation from the outer wall of the furnace is large, and the electric energy cost is increased.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a glass melting furnace with improved heat transfer efficiency from a heating element to a melting tank.

[0011]

That is, according to the present invention, a raw material inlet is provided in an upper portion, a molten glass outlet is provided in a lower portion, and a bottom wall of a melting tank is provided as a heating mechanism for melting glass. A glass melting furnace in which an electric resistance heating element is embedded in a side wall, a cover layer is laminated to cover an inner surface of a melting tank, and a discharge nozzle having a rising portion is extended in an extraction port. Wall and /
Alternatively, the glass melting furnace is characterized in that a cavity is provided between the bottom wall and / or the side wall and the electric resistance heating element along the thickness direction of the side wall.

In the present invention, it is preferable that the cavity has a sectional shape perpendicular to the direction of travel thereof in a slit shape, a circular shape or a rectangular shape.

Further, depending on conditions such as the material and thickness of the highly corrosion-resistant metal forming the cover layer, the depth of the melting tank, the specific gravity of the glass, the melting temperature, etc., the cover layer is formed by the pressure of the molten glass in the melting tank. Deforms to the outside. Therefore, in order to suppress this deformation, it is possible to dispose a plate-shaped body between the inner wall of the melting tank and the outer wall of the cover layer.

The plate-like body is placed in contact with the outer wall of the cover layer between the plate-like body and the refractory. Further, the plate-like body is preferably as thin as possible in order to improve heat conduction from the electric resistance heating element to the highly corrosion-resistant metal that is the cover layer, but on the other hand, as a structural material that suppresses deformation of the cover layer. In order to be used, it is necessary to have sufficient strength. It is preferable that the material of the plate-shaped body is mainly composed of alumina, silicon carbide, or the like having good thermal conductivity. Further, the thickness of the plate-shaped body is preferably about 1 to 10 mm in consideration of heat transfer efficiency and strength.

Further, in the present invention, a large number of through holes may be provided in the plate-like body, which further improves the heat transfer efficiency. Any shape such as a circular shape or a rectangular shape can be applied to the through hole.

[0016]

In the glass melting furnace of the present invention, the heat from the electric resistance heating element is transferred to the inner wall of the melting tank by radiation, so that the heat transfer efficiency is improved and the temperature inside the melting tank is increased.

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the glass melting furnace of the present invention, and FIGS. 2, 3, 5 and 6 show an electric resistance heating element near the bottom wall and its peripheral portion. FIG.

In FIG. 1, an electric resistance heating element 6 for heating is provided inside a refractory 5 constituting the bottom wall 3 and the side wall 4 of the melting tank 1 in parallel with the surfaces of the bottom wall 3 and the side wall 4, respectively. It is arranged. As the electric resistance heating element 6, silicon carbide,
A ferritic alloy or molybdenum dioxide can be used, and the shape is preferably a rod shape or a coil shape.

A cover layer 2 made of platinum is laminated to cover the entire inner wall of the melting tank 1. The cover layer 2 may be made of a noble metal such as a platinum alloy or a heat-resistant metal such as molybdenum depending on the glass composition and melting temperature.

In FIG. 2, the refractory 5 has a cavity 1 so that the electric resistance heating element 6 is exposed along the thickness direction of the bottom wall 3.
0 is bored, and this cavity 10 has an electric resistance heating element 6
Are continuously formed along the length direction of the, and have a groove shape as a whole. With this structure, the inner wall of the melting tank 1 is heated by the radiant heat transfer from the electric resistance heating element 6, so that the heat transfer efficiency is improved.

FIG. 3 shows another embodiment, and FIG. 4 shows A of FIG.
FIG. 3 and 4, a cavity 10 is formed in the refractory 5 along the thickness direction of the bottom wall 3 so as to expose the electric resistance heating element 6, and the cavity 10 is formed.
Are discontinuously formed along the length direction of the electric resistance heating element. Further, the cross-sectional shape perpendicular to the thickness direction of the bottom wall 3 of the cavity 10 may be a circular shape shown in FIG. With this structure, deformation of the cover layer 2 can be suppressed.

FIG. 5 shows still another embodiment. In the figure, the refractory material 5 has a bottom wall 3 similar to the structure shown in FIG.
A cavity 10 is formed along the thickness direction of the electric resistance heating element 6 so that the electric resistance heating element 6 is exposed, and the cavity 10 is formed continuously along the length direction of the electric resistance heating element 6 and has a groove as a whole. It has a shape. Then, the cover layer 2 and the refractory 5
A plate-like body 11 is arranged between the two (in the figure, the upper surface of the refractory 5).

FIG. 6 shows still another embodiment, and FIG. 7 is a sectional view taken along the line AA of FIG. 6 and 7,
Similar to the structure shown in FIG. 3, the refractory 5 has a cavity 10 so that the electric resistance heating element 6 is exposed along the thickness direction of the bottom wall 3.
And a plurality of cavities 10 are formed discontinuously along the length direction of the electric resistance heating element. A plate-like body 11 is disposed between the cover layer 2 and the refractory 5 (the upper surface of the refractory 5 in the figure).
A large number of through holes are formed in the thickness direction. As for the shape of the through hole, other shapes such as a rectangular shape can be applied in addition to the circular shape shown in FIG.

[0024]

As described in detail above, according to the glass melting furnace of the present invention, the heat transfer efficiency from the electric resistance heating element to the melting tank is improved and the temperature in the melting tank is increased. Therefore, the range of glass compositions that can be melted is broadened, which is more practical.

Further, since the difference between the melting temperature and the temperature of the electric resistance heating element is smaller than that of the conventional structure, an inexpensive electric resistance heating element used at a low temperature can be selected.

Since the operating temperature of the electric resistance heating element is relatively low, the frequency of replacement of the electric resistance heating element due to deterioration is reduced and the cost is reduced. Further, since the heat radiation from the outer wall of the melting furnace is reduced, the electric energy cost is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a glass melting furnace of the present invention.

FIG. 2 is a cross-sectional view of essential parts near a bottom wall showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of essential parts near a bottom wall showing another embodiment of the present invention.

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a sectional view of an essential part near a bottom wall showing still another embodiment of the present invention.

FIG. 6 is a sectional view of an essential part near a bottom wall showing still another embodiment of the present invention.

FIG. 7 is a sectional view taken along line AA of FIG. 6;

FIG. 8 is a sectional view showing a conventional glass melting furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting tank 2 Cover layer 3 Bottom wall 4 Side wall 5 Refractory 6 Electric resistance heating element 7 Buried hole 8 Extraction port 9 Discharge nozzle 10 Cavity 11 Plate

Claims (4)

[Claims] 1. An electric resistance heating element is provided on a bottom wall and / or a side wall of a melting tank as a heating mechanism for melting a glass, which has a raw material charging port at an upper part and a molten glass discharging port at a lower part. A glass melting furnace in which a cover layer is embedded and covers the inner surface of the melting tank, and a discharge nozzle having a rising portion at the extraction port is extended. A glass melting furnace, characterized in that a cavity is provided between the bottom wall and / or side wall and the electric resistance heating element along the thickness direction. 2. The glass melting furnace according to claim 1, wherein a cross-sectional shape perpendicular to the traveling direction of the cavity has a slit shape. 3. The glass melting furnace according to claim 1, wherein a cross-sectional shape perpendicular to the traveling direction of the cavity has a circular shape or a rectangular shape. 4. The glass melting furnace according to claim 1, wherein a plate-shaped body is provided between the inner wall of the melting tank and the outer wall of the cover layer.