JPS5820736A - Removal of bubble in glass melting furnace - Google Patents

Abstract

PURPOSE:To remove bubbles in molten glass efficiently, by rotating specific stirrers set in the vicinity of a tip of a neck partitioning a glass melting tank from a cooling tank so that bubbles in the glass are collected at the top. CONSTITUTION:The stirres 10 and 10' are set at both sides in the vicinity of the tip of the neck 4 with a narrow width equipped between the melting tank 1 for clearing molten glass and the cooling tank 5. At least one of the stirrers 10 and 10' having the discs 13 at the top and the blades 12 at the bottom is immersed in molten glass. The stirres 10 and 10' are rotated, so that the molten glass 8 is made to flow outward and downward. Consequently, bubbles in the molten glass 8 are collected at the top of the discs 13, and the bubbles are removed efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing bubbles from molten glass in a glass melting furnace.

An open hearth type glass melting furnace that continuously melts and manufactures glass is composed of a tank, a tank upper structure, and a heat recovery device. The tank consists of a melting tank, a cooling tank, and a partition such as a neck, shadow wall, floater, or throat for dividing these into sections.

A glass batch input from a raw material input port provided at the rear end of the melting tank is heated from above by flames from a burner, gradually melted, and vitrified in the melting zone at the latter half of the melting tank. Joule heat, which is generated by passing an electric current directly from an electrode provided within the glass, may also be used as an auxiliary aid. Next, in the clarification zone in the first half of the melting tank, bubbles are removed from the glass and the glass is homogenized. Between the melting zone and the clarification zone there is an area called a hot spring, where the temperature is the highest, and glass rises from the bottom to the surface. In this hot spring section, heat is supplied to the glass, whereas from this point onwards from the fining zone to the cooling tank, cooling is performed by heat radiation from the glass.

The molten glass sent from the melting tank to the cooling tank must be sufficiently defoamed (clarified), but in order to do so, operations such as raising the temperature level of the entire melting tank may be taken, so that the original degassing cannot be achieved. This will add more energy to the bubble than is required. Furthermore, since bubbles may suddenly occur in excess of the amount that exists under normal conditions, it has been desired to remove the bubbles using some kind of accessory device.

The inventor studied the distribution of bubbles and the flow of glass containing bubbles in a large-scale glass melting furnace in which a melting tank and a cooling tank are separated by a neck, and also studied the methods used to homogenize glass. As a result of giving the stirrer a special structure and considering its installation position and stirring direction, we succeeded in providing the function of removing bubbles in the glass flow, and arrived at the present invention.

According to the present invention, at least one stirrer having a disk on the upper side and a blade on the lower side is installed on each side near the tip of the neck to crush the molten glass. The stirrer is rotated in a direction that draws the flow outward and downward, respectively, and the bubbles in the molten glass are collected above the disk.

The details of the invention are described with reference to the drawings.

FIG. 1 is a schematic plan view of a glass melting furnace, showing the installation position of the stirrer of the present invention.

In the figure, 1 indicates a melting tank, which is equipped with a frit inlet at its rear end and heat storage chambers 8 on both sides. Reference numeral 4 indicates a neck which is a narrow flow path, and a cooling tank 5 is provided in front of the neck. 6 indicates a forehearth (canal) that sends molten glass to the glass forming apparatus.

In this example, pockets 7, 7' are provided on both side walls of the tip of the neck 4, that is, the connection between the neck and the cooling tank 5, and one starter 10, 10' is installed in each of the pockets 7, 7'. The flow of glass along both side walls is directed toward the side walls and downward, respectively.

As shown in FIG. The stirrer is installed so that the blades and disk portions are below the surface of the molten glass 80.

Starter 10 installed on the left side of the tip of the neck is CCW.
(counterclockwise) rotation, and the stirrer 10' performs CW (clockwise) rotation, and both perform pump-down stirring on the molten glass.

The rotating shaft and the blades of the stirrer are, for example, made of a single piece of ceramic material, and a step is provided on the blade to serve as a stop for the disc. For example, the disc consists of Mori and Puden.

A considerable number of bubbles exist in the molten glass at the point where the raw material layer disappears in the melting tank, but by the time it reaches the neck, the large bubbles have floated up and disappeared, and small bubbles have formed in the surface layer, especially along the side walls. It exists.

FIG. 8(A) schematically shows the flow of glass from the neck 4 to the cooling tank before Starsea installation, and here flow C
1C' and d, (many bubbles are distributed in the flow of 1'.

As shown in FIG. 8(B), the starting point is 10,10"i
By installing it on both sides of the neck tip, the flow c, c'
Also, d and d' are extremely biased toward both side walls. Due to this change in the direction of flow, the number of ponds in the product is significantly reduced in a furnace having one canal in the center of the cooling tank, such as a glass furnace for producing float glass.

FIG. 4 is a plan view of the flow of glass in the left pocket portion 7, and FIG. 5 is a plan view of the flow of glass in a cross section taken along the line xx'.

The starter 10 is rotated in the direction of pumping down the glass in the CaW direction. Flows c and d in the plane direction toward the rotating shaft of the stirrer are generated on the surface layer of the molten glass. On the other hand, in the cross-sectional direction, flows shown by e and f occur,
As this flow progresses, the foam components rise to the surface and are collected on the surface layers of flows e and f. Here, if a disk is not provided on the stirrer blade, the glass flow in which the bubbles are collected becomes downward flows g and h and rejoins the main flow, but
Due to the presence of the disk according to the invention, bubbles collect in the f-flow and accumulate on the disk.

Molybdenum is usually used as the material for the disc due to its shape.

The angle of the blade is set in the pump-down direction in order to generate a flow ei toward the rotation axis of the surface layer, but it is set at 45° or more with respect to the horizontal plane, preferably about 1l-15θ to 600°, to the extent that the downflow g does not become too large. do. The thickness of the blades is set to 50 to 70 mm from the viewpoint of stirrer production.

The rotation speed is set according to the size of the surface flow,
It is safe to ensure that the peripheral speed is 15 times or more that of the base flow.

If the substrate flow and peripheral velocity are the same, no effective flow will occur.

Also, if it is done too quickly, entrained bubbles and streaks will occur in that area. The effects of the present invention can usually be obtained by setting the value to about 8 to 20 times L.

The diameter of the disk is 150 to 200111111 as an example.
80~4011LI11 is submerged below the glass surface.

FIG. 6 shows a stirrer that has the function of floating and bursting water bubbles that accumulate on a disk, and here, the disk 18 is the rotating shaft 1.
1 and is left free and fixed to another vibration transmission shaft 14. A vibration generator 15 is attached to the tip of the shaft 14.

A water cooling jacket 16 is provided surrounding the shaft 14, and nitrogen gas is discharged from the upper end of the water cooling jacket 16 from a nitrogen gas supply pipe 17 in order to protect the molybdenum disc 13 and the shaft 14. 1
Reference numeral 8 denotes a ceramic pipe, which is fixed to the disk with a color-blind shaft near the lower end of the water cooling jacket to prevent nitrogen gas from directly contacting the glass and cooling it excessively. The frequency is set to several hundred H2, and vibration in the vertical direction with an amplitude of about 1III#1 is applied.

In another embodiment, a voltage is applied between the disks of a stirrer installed in the pocket/part at the tip of the neck, and electricity is heated through the glass at a power of several tens of kilowatts to locally heat the accumulated bubbles and create bubbles. It is also effective to levitate.

[Brief explanation of the drawing]

Figure 1 is a plan view of a glass furnace showing the installation of a stirrer according to the present invention, Figures 2 (A) and (B) are elevation views showing details of the stirrer, and Figure 8 (A) (13) is a view of the furnace. FIG. 4 is a plan view showing the flow of glass near the stirrer, FIG. 5 is a sectional view taken along line x-x' of No. 4n', and FIG. 6 shows other aspects of the stirrer. FIG. 1... Melting tank 4... Neck 5
...... Cooling tank 8 ...... Molten glass 10.10'... Starve-11...
Rotating shaft 12...Blade 13...Disc 3 Figure 2

Claims (1)

[Claims] A melting tank for melting and vitrifying glass raw materials and refining the molten glass, a cooling tank for cooling the molten glass and adjusting it to a state suitable for molding, and a narrow neck provided between the melting tank and the cooling tank. In this glass melting furnace, at least one stirrer having a disk at the top and a blade at the bottom is installed on each side near the tip of the neck, immersed in the molten glass, to control the flow of the molten glass along both sides of the neck. of,
A method for removing bubbles in a glass melting furnace, comprising rotating a stirrer in a direction that draws the bubbles outward and downward, respectively, to collect bubbles in the molten glass above the disk.