JPS582167B2 - Glass Seizouyo Tank Gama - Google Patents

Description

Detailed Description of the Invention The present invention relates to the structure of a tank kiln for continuously manufacturing glass products such as plate glass, and in particular to a tank kiln that can increase the glass melting load while maintaining the quality of the molten glass base well. Regarding tank kiln structure.

In tank kilns of relatively large capacity for glass production, the melting zone and the fining zone are usually separated by a double barrier with a suitable distance between them. A narrow passage that serves as a flow path for the glass substrate (
(throat) in the center in the width direction.

In the melting zone, a large amount of heat is applied to the input batch (mixed raw materials), converting the crystalline components into an amorphous solution (molten glass base), and in the fining zone, gaseous inclusions are removed from this glass base. be removed.

After passing through the clarification zone, the glass blank is led via a conditioning zone or directly to a shaping zone, where it is shaped into the desired product shape.

The throat connecting the above-mentioned melting zone and clarification zone is narrower than the width of the melting zone, and the glass base material, which is spread throughout the melting zone and has various temperature distributions, is mixed in a narrow convergence and the temperature distribution is adjusted. It plays the role of guiding the water to the clarification area in a uniform state.

There are two main circulation convection currents in the molten glass body within the melting tank that defines the melting zone.

In one of them (hereinafter referred to as cycle A), the glass substrate, which has been cooled and has become denser after receiving the input batch, settles along the batch input side end wall (front wall) of the melting tank together with a part of the input batch. This is a circulating flow that passes through the deep part of the glass base to the center of the tank, emerges to the surface at the highest temperature point (hot spot) in the tank, flows through the surface layer of the base, and returns to the front wall again.

In the other cycle (hereinafter referred to as cycle B), the glass substrate flows from the above-mentioned gushing point through the surface layer of the glass substrate to the throat, and a portion of the glass substrate is extracted from the throat to the clarification area. This is a circulating flow that sinks along the end wall (rear wall), passes through the deep part of the substrate, emerges to the surface at the hot spot, and returns to the throat.

The powdered or granular batches are then uniformly dispersed and mixed into the molten glass matrix in cycle A.
It is melted and homogenized into an amorphous solution during cycle B, particularly during the surface flow of cycle B, which is exposed to a high temperature atmosphere.

As mentioned above, the surface seepage of the deep glass substrate at the hot spot creates two opposite circulation flows, which play an important role in preventing undissolved raw materials from flowing directly into the throat.

During normal operation, when the unit volume of the melting tank and the amount of glass melted per unit time (melting load) are relatively low, the above two circulation convection flows are well balanced. When the batch amount is increased and the melting load is increased, the temperature of the glass substrate in the batch input area of the melting tank increases and the temperature difference with the hot spot increases, so the convection in cycle A, which is driven by this temperature difference, becomes stronger. The area of influence gradually increases, compressing the range of cycle B, and finally, the unmelted batch and the glass substrate containing bubbles come to the surface in the center of the melting tank, which is essential for the completion of melting. Then, the glass flows directly into the throat from the deep part of the melting tank without going through the circulation process of cycle B, leading to a deterioration in the quality of the resulting glass products.

Conventionally, as a means to control the natural convection of the glass substrate in the melting tank, a ventilation nozzle is installed at the bottom of the melting tank near the optimal gushing point of the glass substrate, or a refractory "weir" is installed to force the above-mentioned convection. A method for controlling the range of cycle A and cycle B of is implemented.

However, the former method causes problems such as severe erosion of the bottom and side walls of the melting tank due to forced convection, and air bubbles generated during ventilation that get mixed into the glass substrate, reducing the quality of the glass product being formed. In the latter method, the "weir" becomes a barrier and the transition of the convection glass substrate from cycle A to cycle B is not carried out smoothly, and often "
There is a problem in that a large amount of unmelted components trapped in the weirs flow out, reducing the manufacturing yield of the product.

In view of the above-mentioned problems, the present invention provides a structure for a glass tank kiln that can increase the melting load while maintaining good convection of the molten glass base without using ancillary equipment such as an aeration device or a "weir". The gist is that the distance from the inner edge of the throat opening on the melting tank side to the center of the melting tank is 20% or more, assuming the total width of the melting tank as 100%.
The distance from the outer edge of the opening to the inner surface of the side wall of the melting tank is 10
This is a tank kiln for glass production, characterized in that the throat is positioned so that the

This will be explained in more detail below.

As a result of the research conducted by the present inventor, the strength of the convection of the glass substrate that occurs in a normal glass melting tank is strongest at the center in the width direction of the tank, and becomes weaker as it approaches the side wall. It was found that the strength was strongly influenced by the temperature distribution of the melting tank along the center line of the glass body in the flow direction.

That is, when other conditions are held constant, increasing the amount of cooling for the glass substrate near the widthwise center of the front wall of the melting tank increases the influence area of cycle A; Increasing the amount of cooling to the glass substrate in , the influence zone of cycle B increases.

According to this invention, by shifting the throat installation position from the center position in the width direction of the melting tank toward the side wall, heat dissipation from the glass substrate through the center of the rear wall of the melting tank is maximized. The convection strength of cycle B is improved, so even when the melting load is increased, the influence zone of cycle A is sufficiently suppressed, and unmelted components directly flow from cycle A into the clarification tank through the throat. Good melting is achieved without any problems.

To explain the opening position of the throat in more detail here, if the width of the melting tank is 100% and the distance from the inner edge of the throat opening on the melting tank side to the center of the melting tank is within 20%, the glass flowing through the throat Due to the heat content of the base material, cooling is not achieved sufficiently at the center of the rear wall of the melting tank.
The effect of strengthening the circulating flow cycle B in the glass body does not occur.

Therefore, in the present invention, the above-mentioned distance is limited to 20% or more, and more preferably 25% or more.

Next, if the distance from the outer edge of the throat opening to the inner wall of the melting tank is less than 10% of the full width of the melting tank, glass along the inner wall of the melting tank is almost stagnant due to high viscosity. In order to avoid the possibility that bubbles, foreign matter, etc. on the base surface may be drawn into the throat, the above value is increased by 10% in the present invention.
The content is limited to the above, preferably 15% or more.

In carrying out the present invention, it is desirable that the upper edge of the throat opening on the melting tank side be set lower than the glass base surface in the melting tank, as is generally practiced in the technical field.

This prevents foreign matter, such as air bubbles floating on the surface of the substrate or eroded refractory particles, from flowing into the clarification tank.

In the case of a typical tank kiln for manufacturing plate glass, the distance from the glass base surface in the melting tank to the upper edge of the throat opening is preferably set to 600 mm or more, allowing for a margin.

The lower limit of the cross-sectional area of the throat opening depends on the amount of glass melted, the amount of glass pulled up, the temperature of the glass substrate flowing into the clarification tank, etc., and cannot be set uniformly, but it is generally smaller than the amount of glass pulled up. If it is set too small, the flow velocity of the glass substrate at the throat section will increase and the erosion of the inner wall surface of the throat will become severe.

On the other hand, the throat is usually constructed integrally with highly corrosion-resistant and heat-resistant refractory material, but due to manufacturing technology constraints, the height is 500 m.
Since it is difficult to obtain a throat with a width of about 750 mm or more, if the amount of glass melted is large enough and a single throat would cause the substrate flow velocity to be too high, it is possible to install multiple throats within the range specified by the present invention. .

As an example, in the embodiment described later, a structure is shown in which one is provided on each side in the width direction of the melting tank with respect to the center line of the melting tank.

Further, within the scope of the present invention, a plurality of throats may be provided on each of the left and right sides of the center line of the melting tank, or a plurality of throats may be provided on either the left or the right side.

Increasing the number of throats in this way reduces the glass flow rate per throat and reduces the flow velocity of the glass substrate, which reduces throat erosion and extends the service life.
There is also the advantage that the throat can be manufactured easily.

However, if the distance between adjacent throats becomes too small, the influence areas of the glass substrate inflow of each throat will overlap and cause mutual interference, causing an imbalance in the inflow amount, resulting in the inconvenience that only a particular throat will have a short lifespan. , If multiple throats are provided on each side of the center line of the melting tank, or when multiple throats are provided on either the left or right side, the distance between the adjacent opening edges of adjacent throats is determined by the throat opening width. It is desirable to make it twice or more.

Note that within the range that satisfies the conditions of the present invention, the shape of the throat, the shape of the rear wall of the melting tank adjacent to the throat opening,
The positional relationship between the melting tank and the clarification tank can be arbitrarily selected in consideration of installation conditions and operating conditions.

For example, providing a throat opening with a circular cross section, varying the internal width or height of the throat in the throat length direction, providing the throat at an angle, and placing the bottom of the throat at a lower or higher position than the bottom of the melting tank. installation, and slanting the rear wall of the melting tank toward the throat opening.

It goes without saying that other glass substrate convection control means can also be used, such as providing an aeration device or a "weir" at the bottom of the melting tank.

Next, examples will be described with reference to the drawings.

Figure 1 shows part of a continuous glass tank kiln.
In the figure, 10 is a melting tank, 20 is a clarifying tank, and 30 is a throat.

The melting tank 10 in this embodiment has a length of 10 m and a width of 6 m, and the depth H of the molten glass base 40 is maintained at 1 m.

The throat 30 that communicates the glass substrate 40 in the melting tank 10 and the glass substrate 40 in the clarification tank 20 has an internal dimension of 250 mm in height, 600 mm in width, and 1000 mm in length.
The bottom part 31 of the throat 30 has a rectangular parallelepiped shape.
is leveled with the bottom 11 of the melting tank 10.

Center of melting tank C. The distance LA between L and the inner edge of the opening of the throat 30 is 1500 mm, which is equal to the total width W of the melting tank 10.
This corresponds to 25% of the total.

Further, the distance LB from the inner surface of the melting tank side wall 12 to the outer edge of the opening of the throat 30 is 900 mm, which corresponds to 15% of the full width W of the melting tank 10.

In the tank kiln described above, a raw material batch 5 is charged on the front wall 13 side of the melting tank 10, and this batch 5
It floats in a mountain shape on the 0 surface.

In this glass substrate 40, there is one circulating convection 41 indicated by a counterclockwise arrow in the figure, and this convection (cycle A) 41 causes the mountains of batches 5 to advance and diffuse toward the clarification tank 20 side. In other words, the upper layer of the glass substrate is directed toward the front wall 13 of the melting tank, and after sinking along the front wall 13, it flows through the deep part of the tank 10 to the gushing point 43, where it gushes out to the surface and circulates. repeat.

Another circulating convection (cycle B) 42 advances from the gushing point 43 through the upper layer of the substrate 40 toward the rear wall 14 of the melting tank 10, as shown by the clockwise arrow in the figure, and after sinking at the rear wall 14. The deep part of the substrate returns to the center of tank 10 and springs out at point 4.
At step 3, it gushes out to the surface and repeats the cycle.

Batch 5 is made of molten glass substrate 40 by cycle A41.
At the same time, cycle A41 prevents undissolved batches 5 floating on the surface of the substrate from directly flowing into the clarification tank.

A part of the glass substrate in cycle A41, in which undissolved crystalline components are dispersed and mixed in the amorphous solution, is transferred to cycle B42 at the gushing point 43, and the circulation process of cycle B42, especially the surface In the process of stream 44, melting is promoted and a completely amorphous solution is formed.

In the above tank kiln, as shown by the broken line, Slonit 32
In the conventional structure in which the melting tank 10 opens at the center of the melting tank 10, as the amount of batch input increases, the temperature difference between the melting tank front wall 13 side of the glass substrate and the gushing point 43 increases, and as a result, The convection in cycle A41 increases in strength and its influence area increases, and the melting action area in cycle B42 decreases, so that the quality of the glass substrate flowing into the fining tank 20 deteriorates.

Furthermore, as the amount of batch input increases and the cycle A41 becomes stronger, the glass base containing the unmelted batch flows directly through the slowroad into the clarification tank without passing through surface gushing and circulation in cycle B42.

Such unmelted batch components cause foaming, and therefore the molded product contains a lot of foam, resulting in deterioration in quality or product yield.

On the other hand, in the tank kiln structure of this embodiment, the throat 30 is shifted from the center position of the melting tank 10 toward the side wall 12, so that the outer surface of the central part of the rear wall 14 of the melting tank 10 is exposed to the outside air over a wide range. Therefore, the heat dissipation from the glass substrate in this vicinity is maximized, and convection in cycle B42 is accordingly strengthened.

Therefore, even if the melting load increases and the convection in cycle A41 becomes stronger, the affected area is sufficiently suppressed by this strengthened cycle B42, and a homogeneous and well-melted glass base is sent to the refining tank 20.

The difference in performance between the conventional structure and the structure of this embodiment will become clear from the following explanation.

A throat having the same shape and dimensions as in this example was installed in the center of the melting tank to melt the glass and form a glass plate, and then the number of bubbles contained in the glass plate was measured.

When the amount of glass melted per day is 130 square meters, the number of bubbles with a diameter of 0.5 mm or less that can be seen with the naked eye contained in the glass plate obtained is 30 per 30 grams of glass.
When the glass production volume per day was increased to 145 cubic meters in the same tank kiln, the number of bubbles increased to 50 or more.

With this number, the required glass sheet product quality level is no longer met.

On the other hand, when glass was melted using the tank kiln structure of this example under the same operating conditions as above, the number of bubbles in the glass base obtained when the amount of glass melted per day was 130 The number of bubbles per 30 grams was 10 to 20, and when the number of bubbles was 30 to 40, the amount of glass melted per day could be increased to 1603.

The fuel consumption per unit of glass production in this example was reduced by 3 to 4% compared to the above-mentioned conventional tank kiln structure, and it was confirmed that this example is also effective in terms of energy saving.

FIG. 3 shows another embodiment.

In this example, the melting tank 10 and the clarification tank 20 are communicated through two throats 30.

In this example, the melting tank 10 has a length of 15 m, a width of 8 m,
The depth of the substrate is 1m, and the throat 30 has an inner dimension of 25cm in height.
0mm, width 600mm, length 1000mm rectangular parallelepiped shape, and the same shape and dimensions are the center line C and L of the melting tank.
One unit each is arranged symmetrically in the width direction.

Note that the bottoms of the throats 30 and the bottom of the melting tank 10 are set at the same level.

The distance LA from the center line CL of the melting tank 10 to the inner edge of the opening of the throat 30 is 2100 mm for both throats, which corresponds to 26.25% of the total width W of the melting tank 10.

Further, the distance LB from the inner surface of the melting tank side wall 12 to the outer edge of the opening of the throat 30 is 1300 mm, which corresponds to 16.25% of the melting tank full width W.

After melting 305 square meters of glass per day and forming a glass plate using the tank kiln with the above structure, the number of bubbles was measured and found to be 30 to 40 bubbles per 30 grams of glass, which satisfies the practical quality. It was confirmed that there is.

In addition, in a tank kiln in which only one throat with the same shape and dimensions as this example is installed in the center of the melting tank of the same scale as this example, the practical life of the throat is usually 2.
The structure of this example had a lifespan of 4 years, compared to 1.5 years to 3 years, and it was confirmed that the lifespan of the throat could be extended by increasing the number of bases in the throat and slowing down the flow velocity of the glass substrate in the throat.

[Brief explanation of drawings]

The figure shows an embodiment of the present invention, and only important parts are shown, omitting detailed structures such as the ceiling of the kiln, which are not directly related to the present invention. 1 and 2 are a plan view and a vertical sectional view, respectively, showing the structure of a glass tank kiln with one throat, and FIG. 3 is a plan view showing an example with two throats. 10... Melting tank, 20... Clarifying tank, 3
0...Throat.

Claims (1)

[Claims] 1. A glass melting tank in which at least two circulating convection currents exist in the molten glass base and a subsequent fining tank having approximately the same center line as the melting tank are separated by an appropriate distance, and an opening is provided in both tanks. In a glass tank kiln, in which the glass substrates in both tanks are connected by providing a throat whose width is at least smaller than the width of the melting tank, the entire width of the melting tank is W, and The distance from the inner edge of the tank side opening to the center of the melting tank is L.
A. When LB is the distance from the outer edge of the opening to the inner surface of the side wall of the melting tank, LA/W≧0.2 and LB/W≧0.
A tank kiln for glass production, characterized in that the throat is positioned so that the throat becomes 1.