JPH0550446B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a float glass manufacturing apparatus.

[Prior Art] Float glass is manufactured by continuously cooling clarified molten glass to a predetermined temperature, then supplying the cooled molten glass from a canal to a float bath and forming it into a ribbon of a predetermined thickness. .
In such a method, glass having a slightly different melting history or refractive index is drawn into the canal due to the inhomogeneous glass during the melting process and the convection of the molten glass that occurs during the cooling process. These glasses with different refractive indexes appear in the ribbon and become streak-like defects when observed with transmitted light.

As a method of improving such perspective distortion, it has been proposed to provide a stirrer downstream of the canal or clarification tank to stir the molten glass and homogenize it.

However, in the former method, in which a stirrer is provided in the canal to stir the molten glass, the bath depth of the molten glass is shallow, so molten glass that has not been sufficiently stirred appears in the product, and the perspective distortion cannot be sufficiently improved. To improve this, strong stirring is performed, which entrains air bubbles, which is another drawback.

On the other hand, in the latter method, that is, stirring with a stirrer downstream of the clarification tank, convection occurs during the downstream cooling process, so that once the glass is homogenized, the convection impairs its homogenization when it enters the canal, resulting in sufficient perspective distortion. The problem was that it was not improved.

[Problems to be Solved by the Invention] The present invention aims to solve the above-mentioned difficulties of the prior art and to provide an apparatus capable of manufacturing float glass with extremely low perspective distortion.

[Means for Solving the Problems] That is, the present invention provides a glass bath containing clarified molten glass, a sampling port opened in the glass bath and provided to sample the molten glass above, and a glass bath for storing the molten glass. a conduit passage connected to the mouth and guiding the sampled molten glass downward; a riser part connected to the conduit passage and raising the molten glass guided downward almost vertically; and a molten glass provided in the riser part to raise the molten glass. and a canal section that is connected to the riser section and supplies the homogenized molten glass to the float bath, so that the clarified upper molten glass is homogenized by the stirrer and then supplied to the float bath. The present invention provides an apparatus for manufacturing float glass.

In the present invention, the glass bath is not particularly limited as long as it accommodates molten glass that has been clarified by heating. Specifically, a fining tank that heats and refines molten glass can be mentioned. As a clarification tank, there are conventionally used one-tank types that have a melting section for melting and vitrifying raw materials and a clarification section for refining molten glass, and a single-tank type that has a melting section and a clarification section that clarify the molten glass. It may be of any type, including a two-tank type with separate tanks. The latter, two-bath type, is particularly desirable in the present invention because it provides highly purified glass at relatively low temperatures.

The description will be given below based on the drawings.

FIG. 1 is a vertical sectional view showing the BB sectional view of the device according to the present invention, FIG. 2 is a AA sectional view, and FIG.
It is a partially enlarged view of the figure.

In the figure, 1 is a melting tank, 2 is a clarification tank, 3 is a sampling port, 4 is a riser part, and 5 is a stirrer.

Raw materials are continuously introduced into the melting tank 1 from the left side of the figure to form a raw material layer 6 on the bath surface. This raw material layer is prevented from flowing downstream by the partition wall 7.

Reference numeral 8 denotes a blowout port provided on the side wall, which is equipped with a hydraulic burner (not shown in the figure), and blows out heavy oil together with preheated combustion air to burn it above the raw material layer. This gradually melts the raw material,
This molten glass is supplied to the clarification tank 2 via a throat 9 provided below and a dam wall 10 downstream thereof. The clarification tank has an air outlet 11 similar to the melting tank.
A hydraulic burner is installed to heat the glass inside the tank from the bath surface.

Due to this heating, the molten glass in the clarification tank generates convection currents with a hot spot approximately in the center as shown by the arrow, and air bubbles contained in the glass are strongly heated as they flow on the bath surface and are removed from the glass. Reference numeral 3 denotes a sampling port which opens into the clarification tank, and is located slightly below the bath surface, so that the molten glass above the bath surface, except for those very close to the bath surface, is taken in from the clarification tank. If the sampling port is installed in such a position, even if unmelted substances and glass containing bubbles flow to the downstream end of the clarification tank, they will float on the bath surface, so these impurities can be collected from the sampling port. Very rarely.

Such an effect can be obtained by lowering the upper end of the sampling port to 1/20 of the bath depth below the bath surface;
It is more desirable to lower the bath depth by 10%, and it is especially desirable to lower it by 1/5 of the bath depth. Furthermore, if the lower end of the sampling port is too low, there is a risk of sampling contaminated glass due to contact with refractories, etc., so it is desirable that the lower end be above 1/2 of the bath depth.

Reference numeral 12 denotes an outflow port, which is provided on both side walls of the downstream end of the clarification tank, so that the glass on the bath surface flows out.

As a result, even if impurities such as unmelted substances flow to the downstream end of the clarification tank, these impurities will not remain there and will flow out of the clarification tank from the outlet, so that the impurities will be removed from the sampling port. The risk of being picked up is further reduced.

Reference numeral 13 denotes a conduit connected to the sampling port, which slopes downward, and its downstream end is located at a level slightly lower than the bottom of the clarification tank. This conductive path has a rectangular cross-sectional shape, and if its area is too small, the flow rate of the glass will increase and the erosion of the furnace material will become severe, which is not preferable. The cross-sectional area of the conductive path is preferably such that the average flow velocity of the glass flowing through it is 10 m/h or less.

This conduit is not limited to a structure that slopes toward the downstream, but can also be structured such that it descends vertically from the sampling port.

The riser section 4 is provided in a substantially vertical direction,
Its cross section is circular. The lower part thereof is connected to the downstream end of the conduit, and causes the molten glass from the conduit to flow from below to upward.

Reference numeral 14 denotes an electrode made of molybdenum, which is inserted into the glass through the furnace wall so that electricity can be applied directly to the glass, and by applying electricity, the glass in the vicinity is prevented from being excessively cooled. There is.

A stirrer 5 is provided in the riser section. This stirrer includes a rotating shaft 15 provided in a vertical direction and a plurality of stirring blades 16, 1 fixed to the rotating shaft.
It consists of 7, 18, 19, and 20. These blades each have the shape of a rectangular parallelepiped, and the blade 17 is delayed in phase by 45 degrees from the blade 16, and the blade 18 is delayed in phase by 45 degrees.
is fixed so that it rotates 45 degrees behind the blade 17 in phase. On the other hand, the blade 19 leads the blade 18 in phase by 45 degrees, and the blade 20 leads the blade 19 in phase by 45 degrees.
It is fixed so that it rotates at a constant rate. With this structure, when the rotating shaft is rotated in the direction of the arrow, the lower glass receives an upward force and the upper glass receives a downward force and is stirred. The length of this blade is preferably such that the locus formed by rotation is slightly smaller than the diameter of the riser portion.

Although the structure of the stirrer blades may be other than the rectangular shape as described above, a rectangular shape is particularly desirable because of its simple structure. As a material constituting the stirrer, platinum is preferable because it is hardly eroded by molten glass, is relatively easy to process, and has high strength.

A canal 21 is connected to the riser section and supplies the glass that has been stirred and homogenized by a stirrer in the riser section to the float bath 22 . 23
can be moved up and down with a tow wheel to adjust the amount of glass supplied to the float bath.

[Example] Using the apparatus shown in FIG. 1, float glass having a conventional window glass composition was manufactured at a rate of 100 tons/day.
At this time, the temperature is 1470℃ in the clarification tank and 1400℃ at the sampling port.
It was hot. Cross-sections in the width direction of ribbons produced by varying the rotational speed of the stirrer were projected using transmitted light. During projection, the glass was immersed in a liquid with the same refractive index to avoid refraction and reflection at the interface.
Note that the photograph is enlarged in the thickness direction of the ribbon and reduced in the width direction. Figures 4 and 5 show traces of the photograph. The rotation speed of the stirrer is 5 rpm for the one in Figure 4, and 5 rpm for the one in Figure 5.
It was 10 rpm.

For comparison, we also investigated a model with the stirrer removed. This is shown in Figure 6.

Further, in the apparatus shown in Figs. 1 and 2, float glass is manufactured by stirring with a stirrer downstream of the clarification tank, through a cooling process and a canal, and its cross section is similarly projected and its trace is shown in Fig. 7. .

Separately, these glasses were visually inspected for streak distortion. If the strain of the glass shown in Figure 6 with the worst strain is 8 and that of the glass shown in Figure 5 with the best strain is 0, then the relative value is 4.
The one in the figure was 2, and the one in Figure 7 was 4.

It can be seen from this that the glass produced by the apparatus according to the present invention has extremely excellent homogeneity.

[Effects of the Invention] The float glass manufactured by the apparatus of the present invention has excellent homogeneity, and the streaky distortion in transparency is greatly improved. It is a particularly desirable device for producing float glass.

In particular, it is particularly desirable to provide the sampling port slightly below the bath surface because even if impurities such as air bubbles are floating, there is less possibility that these impurities will be collected.

Furthermore, it is preferable to provide an outlet in the glass bath connected to the sampling port to allow the glass on the bath surface to flow out, since floating impurities will not remain there.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the device according to the invention.
FIG. 2 is a sectional view along line AA in FIG. 1. FIG. 3 is a partially enlarged view of FIG. 1. FIGS. 4 to 7 are traces of photographs of cross sections perpendicular to the plate-making direction. 1... Melting tank, 2... Clarifying tank, 3... Collection port,
4... Riser section, 5... Stirrer, 12...
Outlet, 13...Conduit path, 21...Canal, 2
2...Float bus.

Claims (1)

[Scope of Claims] 1. A glass bath containing clarified molten glass, a sampling port opened in the glass bathtub and provided to collect the molten glass above, and a molten glass connected to the sampling port to collect the molten glass. a conductive path that guides the molten glass downward; a riser section that is connected to the conductive path and raises the molten glass guided downward almost vertically; and a stirrer that is provided in the riser section and stirs and homogenizes the rising molten glass. and a canal section connected to the riser section for supplying the homogenized molten glass to the float bath, wherein the clarified upper molten glass is homogenized by a stirrer and then supplied to the float bath. 2. The apparatus according to claim 1, wherein the sampling port is provided to collect the molten glass slightly below the bath surface. 3. The device according to claim 1, wherein the glass bathtub is a clarification tank. 4 The conduction path has an average flow velocity of molten glass of 1 to
Device according to claim 1, having a cross-sectional area in the range of 10 m/h. 5. The device according to claim 1, wherein the riser portion has a circular cross section.