JPS596254B2 - Glass homogenization method in a vertical electric melting furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for homogenizing glass in a vertical electric melting furnace.

The vertical electric melting furnace has a glass raw material input section at the top,
There is a glass outlet (
It has a throat (sometimes called a throat), and melts and refines glass vertically with a circular or square cross section, such as a hexagon.

In the main body (tank part), electricity is applied directly to the molten glass from an electrode placed through the side wall so as to be in contact with the molten glass, and the Joule heat generated melts and refines the glass.

The glass that flows out from the glass outlet is usually passed through a riser (RI).
The material is guided upwardly by a head differential through a vertically upwardly directed upward flow path called SER, and is then led to a molding machine through a typically horizontally extending forehearth, where it is molded.

One problem with manufacturing glass in the vertical electric melting furnace as described above is that it is difficult to increase the homogeneity of the glass.

In particular, in the case of silicic acid glass, which has high viscosity and high electrical resistance, local temperature differences tend to occur in the melting zone, resulting in localized volatilization of boric acid, a volatile component, and poor mixing of the components. Due to uniformity, it is difficult to avoid a decrease in the homogeneity of the glass.

In order to solve the above-mentioned drawbacks, the present inventor took into consideration the special characteristics of the vertical electric melting furnace and studied various types of stirrers and their arrangement positions, and as a result, arrived at the method of the present invention.

According to the present invention, the rotating shaft and at least two kinds of fluids attached to the rotating shaft and the at least two types of fluids attached to the rotating shaft are directed downward from the upper part of the upper channel that guides the glass flowing out from the glass outlet of the vertical electric melting furnace upward. A rotary stirrer equipped with an upper stirring blade group and a lower stirring blade group that gives a
By rotating the rotary stirrer, a downward flow of the glass is generated near the lower stirring blade group along the rotation axis, and an upward flow of the glass is generated along the rotation axis near the upper stirring blade group, whereby the glass is heated. homogenize.

Embodiments of the invention will now be described with reference to the accompanying drawings.

FIG. 1 shows a cross section of a vertical electric melting furnace equipped with a rotary stirrer according to the method of the invention.

1 shows a glass raw material charging device provided above the furnace.

Reference numeral 2 indicates a raw material input section in the upper part of the furnace, where the frit layer 3 charged therein floats on top of the molten glass 4 below, and is sequentially melted and vitrified from the interface between the two.

The side wall 5 of the furnace body is constructed, for example, in a hexagonal shape, through which a rod-shaped electrode 6, usually made of molybdenum or tin oxide, is provided.

The electrode 6 is in contact with the molten glass and heats the glass by directly passing an electric current therethrough.

The glass melted in the upper part of the furnace and clarified in the lower part exits through a glass outlet (or throat) 7 provided in the lower part of the furnace and ascends a vertically upwardly directed upper channel 8, usually called a riser; Next, the fore berth 9 extends horizontally.
and is led to a molding machine (not shown).

Note that the dashed line indicated by the number 10 indicates the level of glass flowing through the foreverse.

In the above-mentioned upper flow path 8, a rotary stirrer, generally indicated by the number 11, is installed from the opening at the top, and in this example, it rotates clockwise (CW) and stirs the glass flowing through the upper flow path. Homogenize.

Details of the rotary agitator 11 are shown in FIG. 2 (front view), FIG. 3 (top view), and FIG. 4 (right side view).

The rotary agitator 11 consists of a rotating shaft 12 with a circular cross section and a group of stirring blades with a rectangular cross section attached laterally perpendicular to the rotary shaft 12.

In this example, a total of seven stirring blades are attached to the shaft at equal intervals; stirring blades 21, 22, and 23 form the upper stirring blade group, and stirring blades 25, 26, and 27 form the lower stirring blade group. The stirring blade 24 that constitutes the stirring blade group and is located between the two groups functions to correspond to the transition stage of both groups.

Regarding the lower stirring blade group, the second blade 26 from the bottom is rotated clockwise by 45 degrees with respect to the lowest blade 27, and the third blade 25 from the bottom is attached to the blade 27 below. 26
It is mounted in an inclined position rotated further clockwise by an angle of 45 degrees.

The blade 24 is similarly attached to the blade 25 at a position rotated clockwise through an angle of 45 degrees.

Regarding the upper stirring blade group, the blade 23 is rotated at an angle of 45° counterclockwise with respect to the blade 24 below it, and
The wing 22 similarly rotates 4 counterclockwise relative to the wing 23 below it.
It is installed by advancing it at an angle of 5 degrees.

The wing 21 is similarly attached by advancing 45 degrees counterclockwise relative to the wing 22.

When the rotary stirrer having the upper stirring blade groups 21 to 24 and the lower stirring blade groups 24 to 27 (the blade 24 serves both groups or corresponds to a transition stage) configured as described above is rotated clockwise, In the lower stirring blade group, a flow is generated that pulls the glass down along the rotation axis, and the flow spreads outward at the bottom and changes to an upward flow outside the blades (see Fig. 2).

On the other hand, in the upper stirring blade group, the flow of glass spread out below is guided along the axis and changed into an upward flow.

By applying the above-mentioned flow to the glass rising in the upper flow path, the heterogeneous portion existing in the glass is first diffused by the action of the lower stirring blade group, and then drawn to the upper stirring blade group. The glass is exposed to a sufficient cutting action by each blade, and as a result, the inhomogeneities in the glass are dissipated and disappear or are significantly reduced.

Above, the mounting direction of the stirring blades when the rotary stirrer is rotated clockwise has been explained.
As described in Section 1, each member of the upper stirring blade group is sequentially rotated at a fixed angle clockwise from the blade below it, approximately 30 to 60 degrees.
degree, preferably 45 degrees.

On the other hand, in the case of the lower stirring blade group, each member is sequentially installed a certain angle counterclockwise ahead of the blade below it.

In order to cause as much turbulence as possible in the flow of glass, the stirring blades are preferably prismatic or cylindrical with a rectangular, square, circular, or elliptical cross section.

The angle at which the stirring blade is attached to the upper and lower stirring blades is 4.
Although 5 degrees is preferred, variations in the range of about 30 to 60 degrees have essentially no effect on glass flow.

The rotation speed of the rotary stirrer depends on the flow rate of the glass flowing through the upper channel or the degree of heterogeneity of the glass flowing out from the furnace, but when manufacturing silicic acid glass in a glass furnace with a capacity of 10 tty/day, is 2 to 10 r,
p and m were sufficient.

The number of stirring blades of the rotary stirrer is not particularly limited, but 2 to 4 for each of the upper and lower stirring blade groups is sufficient, but it is of course possible to have more.

Due to the rotation of the rotary stirrer described above, an amount of glass is pulled up that exceeds the amount flowing out from the furnace, so to compensate for this, a flow from the top to the bottom is generated.

As a result, if the immersion position of the rotary stirrer is shallow, a downward drawing flow will occur near the furnace wall at the connection between the upper flow path and the foreverse, and there is a risk that a stagnation portion will occur around it.

When melting glass that contains components that easily volatilize, such as borosilicate glass, the components volatilize from the stagnant portion,
This may contribute to the formation of non-uniform glass.

In order to prevent the formation of such stagnant parts, the insertion position of the rotary agitator should be made deep enough. For example, the length of the rotary agitator blade is 30 boxes, the rotation speed is 2 to 10 rpm, 1110 rpm.
If the smallest wing is at least 1 point below the bottom of the foreverse
If the depth is 0 crrL, more preferably 20 crrL or more, generation of stagnant portions can be prevented.

Another means to prevent component volatilization from occurring in the stagnant area is to install a refractory block or the like in contact with or sufficiently immersed in the free surface of the glass at the connection between the upper channel and the foreverse. A cover member is provided to prevent component volatilization or to shift the drawn flow downward from the surface.

The size of the refractory block used is sufficient to cover about half of the glass surface of the connecting portion, that is, the free surface behind the rotating shaft of the stirring device.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a vertical electric melting furnace for carrying out the method of the present invention, FIG. 2 is a front view of an example of a rotary stirrer, and FIG.
The figure shows a plan view of the rotary agitator, and FIG. 4 shows a right side view of the rotary agitator. 1... Glass raw material input device, 2... Raw material input section. 3... Glass raw material layer, 4... Molten glass, 5... Side wall of furnace main body, 6... Electrode, 7... Glass outlet, 8... Upper channel, 9... Foreverse, 10... Glass level, 11... Rotating stirrer, 21-27
...... Stirring blade.

Claims (1)

[Scope of Claims] 1. A raw material input section is provided in the upper part, and an electrode provided in contact with the molten glass from the side wall heats the glass by directly applying electricity to the molten glass. After melting and clarifying the glass, In a vertical electric melting furnace in which glass flows out from a provided glass outlet, the glass flowing out from the glass outlet is guided upward into an upper flow path, and a rotating shaft is connected to the rotating shaft downward from the top of the upper flow path. A rotary stirrer equipped with an upper stirring blade group and a lower stirring blade group that are attached to each other and configured with prismatic or cylindrical stirring blades is installed by immersing it in glass, and by rotating the rotary stirrer, downward stirring is achieved. A vertical column characterized by homogenizing the glass by causing a downward flow of the glass along the rotational axis near the group of blades and an upward flow of the glass along the rotational axis near the upper stirring blade group. Method of homogenizing glass in type electric melting furnace. 2. When the rotary stirrer is rotated clockwise, the stirring blades in the lower stirring blade group are sequentially installed at an angle of about 30 to 60° clockwise ahead of the stirring blades below,
2. The method according to claim 1, wherein the stirring blades in the upper stirring blade group are sequentially mounted at an angle of approximately 30 to 60° counterclockwise ahead of the stirring blades below. 3 When rotating the rotary stirrer counterclockwise, the stirring blades in the lower stirring blade group are sequentially installed approximately 30 to 60 degrees counterclockwise ahead of the lower stirring blade, and 3. The method according to claim 1, wherein the stirring blades in the stirring blade group are installed at an angle of about 30 to 60° counterclockwise ahead of the stirring blades below the stirring blades. 4. The immersion depth of the stirring blade at the top of the rotary stirrer is at least 10 cIIL below the bottom of the forehearth connected to the upper channel and guiding the glass flow in a horizontal direction. the method of. 5. The method according to claim 1, wherein a cover member is provided in contact with or immersed in the glass surface of the connection portion between the upper channel and the forehearth.