JPS5926931A - Electrical smelting method - Google Patents

Abstract

PURPOSE:To carry out the electrical smelting of special glass, stably, without causing bumping, by covering a part of the bubble-containing glass layer covering the whole surface of the smelting tank, with the raw material batch layer. CONSTITUTION:The full electrical smelting of a special glass (e.g. E-glass or S- glass for glass fiber) is carried out by supplying the batch concentratedly to the center of the smelting tank 10 so as to cover the whole surface of the smelting tank 10 with a bubble-containing glass layer 23 covered partially with the intermediate layer 22 and the batch layer 21 leaving the ring-shaped exposed part 23' of the bubble-containing layer 23. The width (l) of the batch layer 21 is preferably about <=1m, and the area of the exposed part 23' of the bubble-containing glass layer is preferably about >=20% of the area of the top face of the smelting tank 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an all-electro-melting method for glass, and in particular to an all-electro-melting method for special glasses for which it has been conventionally considered difficult to do all-electro-melting. Traditionally, melting furnaces fueled by heavy oil were mainly used to melt glass, but in recent years electric melting furnaces have been increasingly adopted because they are energy efficient, cost less to prevent pollution, and are easy to operate. ing. In particular, an all-electric melting furnace that uses only electricity is extremely effective for melting ordinary glass such as soda lime glass. However, special glasses such as E-glass and S-glass for glass fibers are extremely difficult to melt by full electric melting, and although various improvements have been attempted, no effective method has been found.

In total glass melting, a cold tip method is usually used in which the entire surface of the melting tank is covered with a batch. The batch is fed by a special dosing machine that moves over the entire surface of the melting tank so that a batch layer of approximately uniform thickness is formed over the entire surface of the melting tank. This batch tank prevents heat radiation from the melting tank surface.

Figure 1 shows the state above the melting tank of an all-electric melting furnace during the melting of ordinary glass. The top layer of the melting furnace is the batch tank (1), which is usually 10-20 cm thick and uniformly covers the surface of the melting tank. In the batch layer (1), the prepared glass raw materials still exist in a powder state, and easily evaporated water and the like in the batch are evaporated and released into the atmosphere. In the intermediate layer (2) below, the temperature rises considerably, and the easily melted soda components in the batch melt and become liquid, while the less meltable components remain solid and undergo a solid reaction with each other to form a gas ( 2') is released. Therefore, relatively large bubbles, solids, and liquids coexist in the intermediate layer (2). Below the intermediate layer (2) there is a foamed glass layer (3). In the bubble-containing glass layer (3),
The above-mentioned molten components react with other components, and the vitrification reaction progresses considerably, resulting in a pumice-like glass containing a large amount of medium bubbles (3'). Below the bubble-containing glass layer (3) is a transparent molten glass layer (4), in which bubbles (4') float upward, and there are almost no bubbles in this tank.

The batches supplied to the surface of the melting tank undergo a reaction as the temperature rises and gradually move to the lower tank. The temperature gets higher the further down you go. Bubbles (3') (4') in the bubble-containing glass layer (3) pass through the intermediate layer (2), exit the batch tank (1) together with the bubbles (2') in the intermediate layer (2), and are released into the atmosphere. be done.

In the case of special glass, for example, E-glass for glass fibers, the situation is completely different from that of the above-mentioned ordinary glass. In the case of soda-lime glass, etc., the liquid content of the intermediate layer (2) is high in soda and low in clay, so the air bubbles (2') generated in the intermediate layer (2) and the bubble-containing glass tank (3) below ), the bubbles (3') and (4') generated in the molten glass layer (4) also float relatively easily, pass through the batch layer (1), and disappear. However, in the case of E-glass, etc., the content of components that melt at relatively low temperatures, such as soda, is small in the batch, so the intermediate layer (2) has a thin thickness but a high viscosity. Therefore, the generated bubbles cannot float in the intermediate layer (2),
As shown in Figure 2, the intermediate layer (2) and the bubble-containing glass layer (3)
It collects in between and grows into a giant bubble (5). Giant bubble (5
) pushes up the intermediate layer (2) and the batch layer (1), and the batch layer (1) swells. When the giant bubbles (5) grow further, they break through the intermediate layer (2) and cause a bumping phenomenon that blows away the batch powder above. Alternatively, since the bubbles do not escape, the bubble-containing glass layer (3) increases in thickness until it finally reaches the electrode (11) of the melting tank (19) as shown in FIG. In such a state, the electrical resistance of the bubble-containing glass layer is high, so it is difficult for current to flow through it, and the molten state worsens, making it impossible to operate the glass layer.

In the case of full electric melting of special glasses such as E-glass, a batch tank (1
) around 2.5 cm, small cracks occur throughout the batch layer. This crack is caused by the bubble-containing glass layer (3
), from which air bubbles are released and a small bumping phenomenon also occurs, but the glass melting operation can continue. However, since the batch tank (1) is thin, the temperature of the batch layer (1) increases, heat loss from the surface of the melting tank (19) is large, and the working environment is contaminated with dust due to small bumping, which is not desirable. .

The present invention provides a novel all-electric fusing process that overcomes the above-mentioned drawbacks of all-electric fusing of specialty glasses.

As mentioned above, in the conventional all-electric melting furnace, the batch is uniformly supplied to form a batch layer of approximately uniform thickness over the entire surface of the melting tank, but in the method of the present invention, the batch layer is uniformly supplied on the entire surface of the melting tank. It is characterized by forming a part without.

Batch charging of all electric melting furnaces according to the method of the present invention does not require an expensive special charging machine unlike the conventional method, and can be fed centrally to one or several locations using an ordinary simple charging machine. good. Therefore, in the all-electric melting furnace of the method of the present invention, it is possible to cover the upper surface of the melting tank with a heat insulating material, and it is possible to prevent heat loss due to heat radiation from the surface of the melting tank.

Embodiments of the present invention will be described with reference to the drawings. The cross section of the example is a regular hexagon, and the distance between opposing sides is approximately 1.2 m.
A melting tank was used.

In the embodiment shown in FIG. 4, the batch is supplied in a concentrated manner to the center of the melting tank (10), and the batch layer (21) is formed into a convex lens shape or a mountain shape, and the batch layer (21) and the melting tank (19) are fed in a concentrated manner. )
The part (2) where the batch layer (21) and the intermediate layer (22) are not present between the side wall and the bubble-containing glass layer (23) is exposed.
3'). There is no problem even if some intermediate layer (22) exists around the batch layer (21).

Active release of bubbles (bubble breakage) was observed in the exposed portion (23') of the bubble-containing glass layer, and stable melting operation was maintained without cracks or bumping phenomena in the batch tank (21). this is,
The bubbles in the intermediate layer (22) and the bubble-containing glass layer (23) below the batch layer (21) are exposed to the bubble-containing glass exposed portion (23) due to buoyancy.
′) and is released into the atmosphere together with the bubbles in the exposed portion (23′). In order to easily maintain stable melting, the area of the exposed part (23') should be
It is preferable that the area be approximately 20% or more of the area of the top surface of the molten layer.

Further, it is preferable that the width (.) of the batch layer (21) is about 1 m or less. When the width (.) of the batch layer (21) was increased while the power used was kept constant, the amount of batch melted gradually decreased. This is because the bubbles in the bubble-containing glass layer (23) below the batch layer (21) have a longer distance to travel to the exposed part (23'), leaving bubbles and the bubble-containing glass layer (23) gradually becoming thicker. This is thought to be because heat conduction deteriorated and the temperature of the batch layer (21) did not rise.

Alternatively, a doughnut-shaped, striped, island-shaped, etc. batch layer may be formed on the surface of the melting tank, and the other portions may be exposed portions of the bubble-containing glass. In this case, it is preferable that the shortest distance from each part of the batch layer to the exposed part of the bubble-containing glass is about 50 cm or less.

In the embodiment shown in FIG. 5, a separator (6) is provided at the boundary between the batch layer (21) and the exposed portion of the bubble-containing glass (23'). Although a platinum plate was used for the separator (6), other refractories may be used. If the separator (6) is used, even if a slightly large amount of batch is supplied, the thickness of the batch layer (21) will only increase and the exposed portion (23') will be maintained, allowing the glass melting operation to continue stably. Ta. The insertion position of the separator (6) is as shown in FIG. 5(a).
), or it may be placed on the liquid surface of the bubble-containing glass layer (23) as shown in FIG. Separator (
6) does not necessarily need to surround the entire circumference of the batch layer (21), and there may be gaps here and there.

When a ceiling-mounted separator as shown in FIG. 6 is used, the upper surface of the melting tank (10) is thermally sealed, making the melting operation more stable.

The case of a melting tank with a regular hexagonal cross section has been described above, but in the case of a melting tank (30) with a rectangular cross section as shown in FIG. It may be in a state where it extends from the opposite side wall toward the opposite side wall. In this case, in order to continue the melting operation stably, the width (.) of the batch layer (31) should be approximately 1 m or less, and the width between the batch layer (31) and the side wall of the melting tank (30) should be approximately 1 m or less. The width of the gap, i.e. the exposed portion of the bubble-containing glass (33'), is approximately 10
cm or more is desirable, and the exposed part (3
3') desirably occupies 20% or more of the upper surface area of the melting tank (30).

As described above, the method of the present invention makes it possible to industrially perform all-electric melting of special glass, which has been considered difficult in the past, in an extremely stable manner. In particular, it dramatically improves the thermal efficiency of melting special glass in small and medium-sized furnaces, and because it does not use the expensive scattering batch feeder required for conventional all-electric melting furnaces, operating and equipment costs can be reduced. High quality glass can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the vitrification process in the upper layer of the melting tank of an all-electric melting furnace; Figures 2 and 3 are sectional views showing the state of E-glass melting in a conventional all-electric melting furnace; 4, 5, and 6 are sectional views showing an embodiment of the method of the present invention, and FIG. 7 is a plan view showing an embodiment of the method of the present invention. 1, 21, 31; Batch layer, 2, 22; Intermediate layer, 3, 2
3; Bubble-containing glass layer, 6; Separator, 7; Ceiling separator, 23', 33'; Patent applicant for exposed part of bubble-containing glass: Takashi Kageyama■

Claims (5)

[Claims] (1) In full electric melting of glass, the surface of the melting tank is composed of a part covered with the raw material batch and a part mainly made of bubble-containing glass, and the exposed part of the bubble-containing glass is maintained at a substantially constant level during melting. An electric melting method for special glass. (2) The method according to claim 1, wherein the shortest distance from each point of the portion of the melting tank surface covered with the batch to the exposed portion of the bubble-containing glass is approximately 50 cm or less. (3) The method according to claim 1, wherein the batch is concentrated at one location or several other locations on the surface of the melting tank to form a convex lens-shaped batch tank. (4) The method according to claim 1, wherein a separator is provided at the boundary between the batch layer portion on the surface of the melting tank and the exposed portion of the bubble-containing glass. (5) Claims 1 to 4, wherein the proportion of the batch layer on the surface of the melting tank is about 80% or less of the total surface of the melting tank.
The method described in section.