JP6015671B2 - Molten glass production apparatus, molten glass production method, and plate glass production method using them - Google Patents

Description

  The present invention relates to a molten glass manufacturing apparatus, a molten glass manufacturing method, and a manufacturing method of plate glass using them. More specifically, the present invention relates to a molten glass manufacturing apparatus, a molten glass manufacturing method, and a plate glass manufacturing method using them for producing high-quality alkali-free glass with high homogeneity.

  For the production of a glass substrate for a flat panel display (FPD), it is preferable to use an alkali-free glass that does not substantially contain alkali metal ions in order to increase the insulating properties of the glass substrate. Further, alkali-free glass is preferable for the production of a glass substrate for FPD from the viewpoint of a small thermal expansion coefficient.

  In manufacturing a glass substrate for FPD, there is a demand for further improvement in quality, that is, manufacturing a high-quality glass substrate with high homogeneity. For this reason, in the melting tank (melting furnace) which melts a glass raw material and obtains molten glass, various ideas are made in order to improve the homogeneity of molten glass.

  In the melting furnace described in Patent Document 1, the melting furnace is divided into an upstream zone and a downstream zone by a transverse sill, and a molten glass circulation flow (upstream circulation flow, downstream circulation flow) is formed in each zone. , Melting raw materials and homogenizing molten glass. More specifically, the glass raw material is melted by forming an upstream circulation flow in the upstream zone, and the molten glass is homogenized by forming a downstream circulation flow in the downstream zone. In the melting furnace described in Patent Document 1, a bubbler is provided on the upstream side of the crossing sill in order to control the upstream circulation flow and the downstream circulation flow.

The melting furnace (melting tank) described in Patent Document 2 does not have a structure corresponding to the transverse sill in the melting furnace described in Patent Document 1, but includes at least one row of bubblers and at least two opposite burners. It describes using glass to melt and clarify.
However, the melting furnaces described in Patent Documents 1 and 2 are not necessarily suitable for producing high-quality alkali-free glass.
As an index of the melting temperature of glass, T _η , that is, a temperature at which the glass viscosity η becomes 10 ² [dPa · s] is used, but non-alkali glass has a T _η of 1500 to 1760 ° C. Compared with alkali-containing glass such as lime glass, T _η is 100 ° C. or higher, and homogenization is difficult. For this reason, it cannot be sufficiently homogenized in a melting furnace having a layout for general mass production such as soda lime glass described in Patent Documents 1 and 2, and glass products (for FPDs) that require particularly high homogeneity. It was not necessarily suitable for the production of glass substrates and the like.

Further, as described above, the alkali-free glass has a higher T _η than the alkali-containing glass such as soda lime glass, and therefore the temperature of the molten glass in the melting furnace inevitably increases. If the temperature of the molten glass is high, the erosion action of the molten glass on the in-furnace structure is enhanced accordingly. Therefore, in the case of non-alkali glass, there is a step that affects the flow of the molten glass at the bottom of the melting furnace, such as a crossing threshold in the melting furnace described in Patent Document 1 and a fining table in the melting furnace described in Patent Document 2. Then, the erosion of the level | step difference by molten glass and generation | occurrence | production of the impurity by it become a problem.

  In the case of non-alkali glass, the temperature of the molten glass in the melting furnace is inevitably high. Therefore, when a structure having a long downstream zone as in Patent Document 1 or a large melting furnace as in Patent Document 2, It is disadvantageous in terms of energy efficiency because the range of heating using a burner is widened. Further, erosion by the molten glass, generation of impurities due thereto, and change in the flow rate of the molten glass are also problematic.

  In order to solve the above-described problems, the applicant of the present application has proposed a molten glass manufacturing apparatus described in Patent Document 3. In the molten glass manufacturing apparatus described in Patent Document 3, a bubbler (first and second bubblers 13 and 14) provided in the vicinity of the bottom surface of the melting tank 10 for melting the glass raw material and an upper space of the melting tank 10 are heated. By arranging the burner 15 to be in a specific arrangement, the inside of the melting tank 10 can be provided without providing a step structure that affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass flow path. The formation of the molten glass circulation flow (upstream circulation flow 100, downstream circulation flow 101) at the same time is promoted, and the flow rate of the upstream circulation flow 100 and the flow velocity of the downstream circulation flow 101 are in a predetermined relationship. By controlling in this way, it is possible to produce high-quality non-alkali glass with high homogeneity (all symbols in the sentence are as described in Patent Document 3).

Japanese Unexamined Patent Publication No. 9-124323 Japanese Unexamined Patent Publication No. 7-144923 International Publication No. 2011/036939

As described above, by using the glass manufacturing apparatus described in Patent Document 3, high-quality alkali-free glass with high homogeneity can be produced.
However, even when the glass manufacturing apparatus described in Patent Document 3 is used, when the operation of the melting tank is started or when the operating conditions of the melting tank are changed, the molten glass is homogenized for reasons described later. It takes a long time.

When starting the operation of the melting tank, in order to improve the efficiency of the melting work, the glass cullet is poured into the melting tank while the upper space of the melting tank is heated with a burner, and the cullet is melted to dissolve the tank. To ensure the depth of the molten glass. For example, the depth of the molten glass is ensured by melting the cullet until it reaches about 50% or more of the target depth of the molten glass in the melting tank.
The time required to reach about 50% or more of the target depth of the molten glass in the melting tank varies depending on the dimensions of the melting tank. In the case of a melting tank having a glass production amount of 20 to 100 tons / day, since the size thereof is considerably large, it takes a long time to reach about 50% or more of the target depth of the molten glass in the melting tank.

When producing an alkali-free glass, a cullet having an alkali-free glass composition is projected. In the case of an alkali-free glass composition, an easily volatile component such as B ₂ O ₃ or Cl (hereinafter referred to as “volatilization”). The composition of the molten glass differs from the target composition due to volatilization from the molten glass.
Therefore, at the time of starting the addition of the glass raw material, the time until the molten glass reaches the target composition is shortened by adding more raw material of the volatile component than the target composition.

As described above, in the molten glass manufacturing apparatus described in Patent Document 3, the melting tank is supplied by supplying the gases 16 and 17 from the bubblers (first and second bubblers 13 and 14) provided in the vicinity of the bottom surface of the melting tank 10. 10 promotes the formation of a circulating flow of molten glass (upstream circulating flow 100, downstream circulating flow 101) within 10 and sets the flow rate of upstream circulating flow 100 and the flow rate of downstream circulating flow 101 to a predetermined value. The homogenization of the molten glass is promoted by controlling so as to satisfy the relationship (all symbols in the sentence are as described in Patent Document 3).
However, the volatilization component having a low molecular weight has a lower specific gravity than other glass raw materials, so that the light raw material does not dissolve in the upstream circulation flow and floats on the upstream circulation flow to the downstream side of the dissolution tank. And tend to move. For this reason, it takes a long time to homogenize the molten glass in the melting tank.

  In addition, when the operating conditions of the melting tank are changed, the molten glass may stay on the upstream side of the melting tank from the upstream circulation flow. Such stagnation of the molten glass causes the homogenization of the molten glass to be delayed. Such stagnation of the molten glass is, for example, when the input amount of the glass raw material is increased, or when a glass raw material having a lighter specific gravity than the molten glass in the melting tank is input for the purpose of adjusting the specific gravity of the glass to be produced. Tend to happen. Moreover, there exists a tendency which occurs when the depth of the molten glass in a melting tank falls for some reason, or when the temperature of the molten glass which exists in the upstream of a melting tank falls.

  In order to solve the problems of the prior art described above, the present invention can promote homogenization of molten glass even when the operation of the melting tank is started or when the operating conditions of the melting tank are changed. An object of the present invention is to provide a molten glass production apparatus, a molten glass production method, and a plate glass production method using them, which are suitable for producing high-quality, high-quality alkali-free glass.

In order to achieve the above-described object, the present invention is a molten glass manufacturing apparatus having a melting tank for melting a glass raw material,
The dissolution tank has a burner for heating the upper space of the dissolution tank,
When the length of molten glass flow path of the melting tank and L _F, and midstream bubbling unit is provided at a position where the distance from the upstream side of the dissolution tank becomes 0.4L _F ~0.6L _F , and the upstream region bubbling unit provided at a position where the distance from the upstream side of the dissolution tank becomes 0.05L _F ~0.2L _F,
The midstream bubbling unit is composed of a bubbler group in which a plurality of bubblers are provided in the vicinity of the bottom surface of the melting tank over the width direction of the molten glass flow path of the melting tank,
The upstream region bubbling unit is composed of a plurality of bubblers provided in parallel in the width direction of the molten glass flow path of the melting tank in the vicinity of the bottom surface of the melting tank,
The upstream bubbling unit includes at least a pair of bubblers provided at positions symmetrical with respect to the center in the width direction of the molten glass flow path.

  Moreover, this invention is a molten glass manufacturing method which manufactures molten glass, supplying gas from each bubbler which comprises the said middle stream area bubbling unit and the said upstream area bubbling unit using the molten glass manufacturing apparatus of this invention. provide.

  Moreover, this invention provides the plate glass manufacturing method which shape | molds the molten glass obtained by the molten glass manufacturing method of this invention to plate glass.

According to the molten glass manufacturing apparatus and the molten glass manufacturing method of the present invention, homogenization of the molten glass can be promoted even when the operation of the melting tank is started or when the operating conditions of the melting tank are changed. It is suitable for production of high-quality, high-quality alkali-free glass, and the time required for production of the alkali-free glass can be shortened.
Since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and high transparency, it is suitable for manufacture of the board | substrate for FPD.

FIG. 1 is a cross-sectional view of an embodiment of a melting tank in the molten glass production apparatus of the present invention. FIG. 2 is a plan view of the dissolution tank 10 shown in FIG. However, the upper wall surface of the dissolution tank 10 is omitted.

The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of one embodiment of a melting tank in the molten glass production apparatus of the present invention, and FIG. 2 is a plan view of the melting tank shown in FIG. However, the upper wall surface of the dissolution tank 10 is omitted for easy understanding.
A glass raw material inlet 11 is provided at the upstream end of the melting tank 10. The glass raw material charged from the charging port 11 is melted by heating by the burner 16 to become molten glass G, and is held in the melting tank 10. A discharge port 12 for discharging the molten glass G to the next process is provided at the downstream end of the melting tank 10. The discharge port 12 communicates with the downstream conduit 20.

In the vicinity of the bottom surface of the dissolution tank 10 shown in FIGS. 1 and 2, an upstream region bubbling unit and a midstream region bubbling unit each including a plurality of bubblers 13, 14 and 15 are provided. As will be described in detail later, the bubbler 13 constituting the upstream bubbling unit is provided in the upstream area of the molten glass flow path of the melting tank 10, and the bubblers 14 and 15 constituting the midstream bubbling unit are provided in the melting tank 10. Is provided in the middle region of the molten glass flow path.
Burners 16 are arranged on both side surfaces of the melting tank 10 shown in FIGS. 1 and 2 so as to be positioned above the molten glass G held in the melting tank 10. The burners 16 are provided at equal intervals over the entire length of the dissolution tank 10 except for an exception part to be described later.

The upstream region bubbling unit includes a plurality of bubblers 13 provided in the vicinity of the bottom surface of the melting tank 10 in parallel in the width direction of the molten glass flow path of the melting tank 10.
In the aspect shown in FIG. 2, the upstream region bubbling unit is composed of a pair of bubblers 13 provided at symmetrical positions with respect to the center in the width direction of the molten glass flow path of the melting tank 10.

  As will be described in detail later, in the melting tank 10 in the molten glass production apparatus of the present invention, patent documents are provided at the bottom of the molten glass flow path by supplying gases 18 and 19 from the bubblers 14 and 15 constituting the midstream bubbling unit. Circulating flow of molten glass G in the melting tank 10 (upstream circulating flow 100, downstream circulating flow 101) without providing a step structure that affects the molten glass flow as described in 1 and 2 And the flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 can be controlled to have a predetermined relationship. Hereinafter, in the present specification, supplying the gases 18 and 19 from the bubblers 14 and 15 constituting the middle basin bubbling unit may be referred to as “bubbling from the middle basin bubbling unit”.

However, with only bubbling from the midstream basin unit, it takes a long time to homogenize the molten glass G in the melting tank 10 when the melting tank 10 is started or when the operating conditions of the melting tank are changed.
When producing alkali-free glass, at the start of the operation of the melting tank 10, in order to shorten the time until the molten glass G in the melting tank 10 reaches the target composition, more raw material of the volatilizing component is added than the target composition. However, the volatilization component having a low molecular weight has a lower specific gravity than other glass raw materials, so that the light raw material does not dissolve in the upstream circulation flow 100 and floats on the upstream circulation flow 100. Since there is a tendency to move to the downstream side of the melting tank 10, it takes a long time to homogenize the molten glass G in the melting tank 10.
Further, when the operating conditions of the melting tank 10 are changed, the molten glass G may stay on the upstream side of the melting tank 10 with respect to the upstream circulating flow 100. Hereinafter, the retention of the molten glass G on the upstream side of the melting tank 10 relative to the upstream circulation flow 100 is referred to as “the retention of the molten glass G on the upstream side of the melting tank 10”.
Since the retention of the molten glass G on the upstream side of the melting tank 10 causes the homogenization of the molten glass G in the melting tank 10 to be delayed, the molten glass in the melting tank 10 after the change of the operating conditions of the melting tank 10 is performed. It takes a long time to homogenize G.

In the dissolution tank 10, the molten glass in the dissolution tank 10 is supplied at the start of the operation of the dissolution tank 10 or when the operation conditions of the dissolution tank are changed by supplying the gas 17 from the bubbler 13 constituting the upstream region bubbling unit. The homogenization of G can be promoted. Hereinafter, in the present specification, supplying the gas 17 from the bubbler 13 constituting the upstream region bubbling unit may be referred to as “bubbling from the upstream region bubbling unit”.
At the start of the operation of the dissolution tank 10, the bubbling from the upstream region bubbling unit is carried out to promote the dissolution of the volatile component raw material into the upstream circulation flow 100. Thereby, homogenization of the molten glass G in the melting tank 10 is promoted.
In addition, even when the operating conditions of the melting tank 10 are changed, the stagnation of the molten glass G on the upstream side of the melting tank 10 can be suppressed by carrying out the bubbling from the upstream region bubbling unit. Can eliminate the retention of the molten glass G.

In order to exhibit the effect mentioned above, the bubbler 13 which comprises an upstream area bubbling unit needs to satisfy | fill the conditions described below in relation to the length of the molten glass flow path of the melting tank 10. FIG.
In the dissolving tank 10 in the molten glass producing apparatus of the present invention, the length of molten glass flow path of the dissolution tank 10 when the L _F, until each bubbler 13 constituting the upstream region bubbling unit from the upstream end of the molten glass flow path The distance is 0.05L _{F to} 0.2L _F.
If the distance from the upstream end of the molten glass flow path to the bubbler 13 is less than 0.05 L _F, the upstream side wall surface of the dissolution tank 10, because the respective bubblers 13, the distance too close, from the upstream region bubbling unit There is a possibility that erosion of the upstream side wall surface of the dissolution tank 10 may be promoted by performing the bubbling.
On the other hand, if the distance from the upstream end of the molten glass flow path to the bubbler 13 is greater than 0.2L _F , the upstream side of the melting tank 10 can be upstream even when bubbling from the upstream bubbling unit is performed at the start of operation of the melting tank 10. The melting of the raw material of the volatile component into the circulating flow 100 cannot be promoted, and the homogenization of the molten glass G in the melting tank 10 cannot be promoted. Further, when the operating conditions of the melting tank 10 are changed, even if bubbling from the upstream region bubbling unit is performed, the retention of the molten glass G on the upstream side of the melting tank 10 cannot be suppressed.
In the melting tank 10 in the molten glass production apparatus of the present invention, the distance from the upstream end of the molten glass flow path to each bubbler 13 constituting the upstream region bubbling unit is preferably 0.1 L _{F to} 0.2 L _F. More preferably, it is 0.1L _{F to} 0.15L _F.

As described above, in the melting tank 10 shown in FIG. 2, the pair of bubblers 13 are provided at positions symmetrical to the center in the width direction of the molten glass flow path of the melting tank 10. Hereinafter, in the present specification, the fact that the bubbler 13 is provided at a position that is symmetric with respect to the center in the width direction of the molten glass flow path of the melting tank 10 is “being symmetrical in the width direction of the melting tank 10. A bubbler 13 is provided. " In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, the bubbler 13 needs to be provided so as to be symmetric in the width direction of the melting tank 10. An example in which the bubbler 13 is not provided so as to be symmetric in the width direction of the dissolution tank 10 is a case where one of the pair of bubblers 13 shown in FIG. 2 is not provided. In this case, when bubbling from the upstream region bubbling unit is performed, the flow of the molten glass G in the melting tank 10 is not symmetric with respect to the width direction of the melting tank 10, but toward the side wall of the melting tank 10. Since the flow of this is promoted, the side wall of the dissolution tank 10 may be eroded. Further, the upstream circulating flow 100 may be disturbed, and the homogenization of the molten glass G may be adversely affected.
Further, as an example in which the bubbler 13 is not provided so as to be symmetric in the width direction of the bubbler melting tank 10, one bubbler 13 is provided near the center in the width direction of the molten glass flow path of the melting tank 10. There are cases. Also in this case, when the bubbling from the upstream region bubbling unit is performed, the flow of the molten glass G toward the side wall of the melting tank 10 is promoted, so that the side wall of the melting tank 10 may be eroded.
In addition, since it is necessary to provide the bubbler 13 so that it may become symmetrical in the width direction of the dissolution tank 10, it is necessary to provide at least two bubblers 13. When the number of bubblers 13 is increased from two, the number of bubblers 13 needs to be an even number. For example, when four bubblers 13 are provided, it is necessary to provide two pairs of bubblers 13 so as to be symmetrical in the width direction of the dissolution tank 10.

It is preferable that the bubbler 13 which comprises an upstream area bubbling unit satisfy | fills the conditions described below also in relation with the width | variety of the molten glass flow path of the melting tank 10. FIG.
In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, when the width of the molten glass flow path of the melting tank 10 is W, each bubbler 13 constituting the upstream region bubbling unit is centered in the width direction of the molten glass flow path. It is preferable to be provided at a position where the distance from the center becomes 0.25 W or more.
If the distance from the center in the width direction of the molten glass flow path is smaller than 0.25 W, the bubbler 13 is provided near the center in the width direction of the molten glass flow path. Since the flow of the molten glass G in the direction of the side wall of the melting tank 10 is promoted, the side wall of the melting tank 10 may be eroded.
In the melting tank 10 in the molten glass production apparatus of the present invention, each bubbler 13 constituting the upstream bubbling unit is provided at a position where the distance from the center in the width direction of the molten glass flow path is 0.27 W or more. More preferably, it is more preferably provided at a position of 0.4 W or more.

However, it is preferable that each bubbler 13 which comprises an upstream area bubbling unit is provided in the position where the distance from the side wall of the dissolution tank 10 becomes 400 mm or more. When the bubbler 13 is provided at a position where the distance from the side wall of the dissolution tank 10 is smaller than 400 mm, the distance between the side wall of the dissolution tank 10 and the bubbler 13 is too close, so that the bubbling from the upstream area bubbling unit is performed. The erosion of the side wall of the dissolution tank 10 may be promoted.
In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, it is more preferable that each bubbler 13 constituting the upstream region bubbling unit is provided at a position where the distance from the side wall of the melting tank 10 is 1000 mm or more.

The length L _F of the molten glass flow path of melting tank 10 of the present invention varies depending on the width W of the molten glass flow path, preferably 10 to 30 m, more preferably from 10 to 25, more preferably Is 15-22 m.
On the other hand, the width W of the molten glass channel is preferably 5 to 10 m, more preferably 5.5 to 9 m, and still more preferably 6.5 to 8 m.

In the melting tank 10 shown in FIGS. 1 and 2, each bubbler 13 constituting the upstream region bubbling unit is provided further upstream than the burner 16 located on the most upstream side in the length direction of the molten glass flow path. Yes. Thus, in the melting tank 10 in the molten glass manufacturing apparatus of the present invention, each bubbler 13 constituting the upstream region bubbling unit is provided further upstream than the burner 16 located on the most upstream side. It is preferable for exerting an effect of promoting homogenization of the molten glass by carrying out bubbling from the upstream region bubbling unit.
In some dissolution tanks, a flue for discharging combustion exhaust gas from the burner 16 may be provided further upstream than the burner 16 located on the most upstream side. In such a case, it is preferable that each bubbler 13 constituting the upstream region bubbling unit is provided further upstream than the flue.
However, in order to exert the effect of promoting homogenization of the molten glass by carrying out bubbling from the upstream region bubbling unit, in the length direction of the molten glass flow path, each bubbler 13 constituting the upstream region bubbling unit, It is preferable that the distance from the most upstream burner 16 is not too large. In the melting tank 10 in the molten glass production apparatus of the present invention, the distance in the length direction of the molten glass flow path between each bubbler 13 constituting the upstream region bubbling unit and the burner 16 located on the most upstream side is within 2000 mm. Preferably, it is within 1500 mm, more preferably within 1000 mm.

The midstream bubbling unit is composed of a bubbler group in which a plurality of bubblers 14 and 15 are provided in the vicinity of the bottom surface of the melting tank 10 over the width direction of the molten glass flow path of the melting tank 10.
In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, the bubbling from the middle-stream bubbling unit affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass flow path. Without providing a step structure, the formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10 is promoted, and the flow rate and downstream of the upstream circulating flow 100 are reduced. The flow rate of the side circulation flow 101 can be controlled to have a predetermined relationship.
In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, it is not necessary to provide a step structure in which erosion by the molten glass is a problem at the bottom of the molten glass flow path, so that T _η is 1500 to 1760 ° C. It is suitable for the production of an alkali-free glass that is 100 ° C. or more higher than the alkali-containing glass.

In the melting tank 10 shown in FIGS. 1 and 2, the midstream bubbling unit has two bubbler groups whose positions in the length direction of the molten glass channel of the melting tank 10 are different from each other, that is, across the width direction of the molten glass channel. The first bubbler group is provided with a plurality of bubblers 14 and the second bubbler group is provided with a plurality of bubblers 15 across the width direction of the molten glass flow path.
However, in the melting tank 10 in the molten glass manufacturing apparatus of the present invention, the midstream bubbling unit may have a single bubbler group. Specifically, for example, only one of the above-described first bubbler group and second bubbler group may be included.
However, the middle basin bubbling unit is composed of a plurality of bubbler groups whose positions in the length direction of the molten glass flow path of the melting tank 10 are different from each other. It is preferable when exhibiting.
In the case where the middle basin bubbling unit is constituted by a plurality of bubbler groups, it may be constituted by three or more bubbler groups whose positions in the length direction of the molten glass flow path of the melting tank 10 are different from each other. As in the melting tank 10 shown in FIG. 2, it is more preferable from the viewpoint of cost effectiveness that the melting tank 10 is composed of two bubbler groups whose positions in the length direction of the molten glass flow path are different from each other.

In order to exert the above-described effects, the bubblers 14 and 15 constituting the midstream bubbling unit must satisfy the following conditions in relation to the length of the molten glass flow path of the melting tank 10.
In the melting tank 10 in the molten glass production apparatus of the present invention, when the length of the molten glass flow path of the melting tank 10 is L _F , each bubbler (first first) of the midstream bubbling unit from the upstream end of the molten glass flow path. The distance to each of the bubblers 14 and 15 constituting the second bubbler group) is 0.4L _{F to} 0.6L _F.
Therefore, compared with the conventional melting tank (melting furnace) as described in Patent Documents 1 and 2, the length of the melting tank 10 is short, and the length of the part forming the downstream circulating flow in the melting tank is also short. .

Here, as in the melting tank 10 shown in FIGS. 1 and 2, two bubbler groups (first bubbler group and second bubbler group) having different positions in the length direction of the molten glass flow path of the melting tank 10 are mutually different. It is preferable that the distance from the upstream end of the molten glass flow path to the bubblers 14 and 15 constituting each bubbler group satisfy the following respectively.
Preferably the distance from the upstream end of the molten glass flow path to each bubbler 14 constituting the first bubbler group is 0.4L _F ~0.5L _F, it is 0.43L _F ~0.46L _F Is more preferable. On the other hand, it is preferable that the distance to the bubbler 15 constituting the second bubbler group from the upstream end of the molten glass flow path is 0.45L _F ~0.55L _F, in 0.46L _F ~0.53L _F More preferably.

As shown in the melting tank 10 shown in FIGS. 1 and 2, it is composed of two bubbler groups (first bubbler group and second bubbler group) whose positions in the length direction of the molten glass flow path of the melting tank 10 are different from each other. If, each bubbler 14 constituting the first bubbler group, and a distance between each bubbler 15 constituting the second bubbler group and L _P, that L _P is 500 to 1000 mm, in the above-mentioned It is preferable for exhibiting the effect of carrying out bubbling from the basin bubbling unit, and L _P is more preferably 600 to 800 mm.

  Moreover, the pitch p between each bubbler which comprises each bubbler group of a middle-stream area bubbling unit, ie, the distance between each bubbler in the width direction of the molten glass flow path of the melting tank 10, is 400 to 700 mm. It is preferable in order to exhibit the effect by carrying out the bubbling from the above-mentioned middle basin bubbling unit while considering the viewpoint of cost effectiveness.

As shown in the melting tank 10 shown in FIGS. 1 and 2, it is composed of two bubbler groups (first bubbler group and second bubbler group) whose positions in the length direction of the molten glass flow path of the melting tank 10 are different from each other. In this case, when the flow path direction of the molten glass in the melting tank 10 is used as an axis, the bubbler 14 constituting the first bubbler group and the bubbler 15 constituting the second bubbler group do not exist on the same axis. It is preferable that they are arranged.
In the dissolution tank 10 shown in FIG. 2, the protrusions of the bubblers 14 constituting the first bubbler group and the protrusions of the bubbler 15 constituting the second bubbler group are arranged in a staggered manner. The protruding port of the bubbler 14 constituting the bubbler group and the protruding port of the bubbler 15 constituting the second bubbler group do not exist on the same axis.
In such an arrangement, even if one of the protruding ports of the bubbler 14 constituting the first bubbler group stops functioning, the second bubbler group arranged in a staggered pattern on the downstream side The presence of the protruding port of the constituting bubbler 15 does not impair the effect of promoting the formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10, and The flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 can be controlled to have a predetermined relationship.

In the melting tank 10 in the molten glass production apparatus of the present invention, the constituent materials of the bubbler 13 constituting the upstream region bubbling unit and the bubblers 14 and 15 constituting the midstream region bubbling unit are excellent in flame resistance and corrosion resistance to the molten glass. Therefore, platinum or a platinum alloy is preferable.
Further, the gas 17 supplied from the bubbler 13 constituting the upstream region bubbling unit and the gases 18 and 19 supplied from the bubblers 14 and 15 constituting the midstream region bubbling unit include the molten glass G and the bubblers 13 and 14. , 15 and the like that do not adversely affect the components of the dissolution tank 10 are preferably used. Specific examples of such a gas include air, nitrogen, oxygen, helium, and argon. When platinum or a platinum alloy is used as the constituent material of the bubblers 13, 14, and 15, the gases 17, 18, and 19 supplied from the bubblers 13, 14, and 15 are oxygen such as nitrogen, helium, and argon. It is preferable to use a gas that does not contain. Of these, nitrogen is particularly preferred.

Burners 16 are provided at equal intervals over the entire length of the dissolution tank 10 on both side surfaces of the dissolution tank 10 shown in FIGS. However, the burner 16 is not provided above the bubbler 15 constituting the second bubbler group.
The reason why the burner 16 is not provided above the bubbler 15 constituting the second bubbler group is a mode of suitable control in the molten glass production method of the present invention described later (control 2). This is because the ambient temperature T ₂ above the bubbler 15 constituting the second bubbler group needs to be lower than the ambient temperature T ₁ above the bubbler 14 constituting the first bubbler group.
When (Control 2) is performed, it is preferable that the bubbler 15 constituting the second bubbler group and the burner 16 closest to the downstream side with respect to the bubbler 15 are arranged to some extent apart from each other. Specifically, it is preferable that the distance L _B2 between the bubbler 15 constituting the second bubbler group and the burner 16 closest to the downstream side with respect to the bubbler 15 is 800 mm or more.

However, if the bubbler 15 constituting the second bubbler group and the burner 16 closest to the downstream side with respect to the bubbler 15 are separated too much, the ambient temperature above the bubbler 15 constituting the second bubbler group is increased. On the other hand, it may become too low, and problems such as insufficient homogenization of the molten glass may occur. Moreover, the temperature of the molten glass G discharged | emitted from the discharge port 12 provided in the downstream edge part of the melting tank 10 becomes low, and when depressurization defoaming is performed in a post process, it is difficult to defoam. May occur. For this reason, L _B2 is preferably 2500 mm or less. Incidentally, L _B2 is preferably an 1000 to 2000 mm, L _B2 is more preferably 1000～1600Mm.

In addition, if the (control 2), above the ambient temperature T ₂ of the bubbler 15 constituting the second bubbler group, lower than the atmosphere above the temperature T ₁ of the bubbler 14 constituting the first bubbler group Therefore, the distance L _B1 between the bubbler 14 constituting the first bubbler group and the burner 16 closest to the upstream side with respect to the bubbler 14 and the above-mentioned distance L _B2 are _expressed as L _B2 It is preferable that the relationship is> L _B1 . Therefore, as shown in FIG. 2, it is preferable that the burner 16 is provided above the bubbler 14 which comprises a 1st bubbler group. With this arrangement, the ambient temperature T ₂ above the bubbler 15 constituting the second bubbler group is made lower than the ambient temperature T ₁ above the bubbler 14 constituting the first bubbler group. Can do.
In the present invention, L _B2 −L _B1 ≧ 300 mm is preferable, L _B2 −L _B1 ≧ 500 mm is more preferable, and L _B2 −L _B1 ≧ 800 mm is further preferable.

On the other hand, in the dissolution tank 10 shown in FIG. 2, the nearest burner 16 is provided above the bubbler 14 constituting the first bubbler group. However, as long as the relationship of L _B2 > L _B1 is satisfied, the first bubbler group And the burner 16 nearest to the upstream side of the bubbler 14 may be arranged apart from each other to some extent. However, if the bubbler 14 constituting the first bubbler group and the burner 16 closest to the upstream side of the bubbler 14 are separated too much, the ambient temperature above the bubbler 14 becomes too low and the upstream side circulation flow 100 is weakened. There is a possibility that problems such as insufficient melting of the glass raw material and insufficient homogenization of the molten glass G in the downstream region of the melting tank 10 may occur. From such a viewpoint, it is preferable that L _B1 is 2000 mm or less. Incidentally, L _B1 is more preferably 500～1500Mm.

  Moreover, although the pitch between the adjacent burners 16 is based also on the kind of burner 16, and the layout of the dissolution tank 10, 600-2600 mm is preferable and 800-2400 mm is more preferable.

Combustion in the burner 16 can be performed by mixing the fuel with oxygen gas and burning it, or mixing the fuel with oxygen gas and air and burning it. By using these methods, moisture can be contained in the molten glass. In the post-process of the molten glass sent from the melting tank 10 to the downstream conduit 20, when the bubbles in the molten glass are defoamed by vacuum degassing, the molten glass preferably contains moisture. Therefore, the combustion as described above is preferable.
In order to prevent deposits on the inner wall brick surface of the melting tank 10 (for example, glassy material eluted from the bricks, volatilized materials or molten glass) from falling on the burner portion, the melting tank 10 An eaves (not shown) is preferably provided on the upper wall of the burner 16 on the inner wall.

The constituent material of the melting tank 10 in contact with the molten glass G is required to be excellent in heat resistance and corrosion resistance to the molten glass. Therefore, a refractory brick containing ZrO ₂ is used. of the bottom surface of the dissolving tank 10, in a portion of the first 0.1L from bubbler 14 of the bubbler group upstream _{F ~0.3L F,} ZrO ₂ is not more than 97% 85% by mass%, It is preferable to use a glassy hot-melt refractory material whose main part is SiO ₂ . When the temperature of the molten glass flowing through the melting tank 10 is higher on the upstream side than on the downstream side, and is a preferred control mode in the molten glass production method of the present invention described later (control 1). Since the flow rate of the gas 18 from the bubbler 14 constituting the first bubbler group is larger than the flow rate of the gas 19 from the bubbler 15 constituting the second bubbler group, the melting tank forming the molten glass flow path This is because the constituent material of the bottom surface 10 is easily eroded.
Further, from the viewpoint of preventing erosion of the constituent material of the bottom surface of the melting tank 10 forming the molten glass flow path, it is preferable to use the above-described hot-melt refractory also for the peripheral portion of the bubbler 13 constituting the upstream region bubbling unit. .
In addition, when the length L _F of the molten glass flow path of the melting tank 10 is 10 to 30 m (preferably 10 to 25 m, more preferably 15 to 22 m) as described above, the upstream region bubbling unit is configured. It is preferable to use the above-mentioned hot-melt refractory in the range of 100 to 600 mm, preferably in the range of 150 to 400 mm, in the length direction of the molten glass flow path with the bubbler 13 as the center.
Further, as described above, when the width W of the molten glass channel of the melting tank 10 is 5 to 10 m (preferably or 5.5 to 9 m, more preferably 6.5 to 8 m), the upstream bubbling unit The above-mentioned hot-melt refractory in the range of 100 to 600 mm, preferably in the range of 150 to 400 mm, more preferably in the range of 150 to 300 mm, respectively, in the width direction of the molten glass flow path, centering on the bubbler 13 constituting Is preferably used.
In these cases, the thickness of each hot-melt refractory is preferably 50 to 400 mm, and preferably two or three hot-melt refractories are laminated. Furthermore, 2-5 layers of other ZrO ₂ -containing refractory bricks can be laminated outside the layer of the hot-melt refractory thus formed. In addition, it is preferable to comprise all the parts which contact | connect the molten glass G of the melting tank 10 with the hot-melt refractory material of the said composition. Moreover, each refractory brick can be laminated | stacked via stamp materials, such as an alumina zircon material.
In order to prevent molten glass from entering from the joints of the refractory bricks at the bottom of the melting tank 10 and eroding the refractory bricks, the refractory bricks are stacked and arranged under the joints so as to close the joints. preferable.
It is preferable that cooling means by air cooling or water cooling for cooling the refractory brick is provided on the outer side of the refractory brick at the bottom of the melting tank 10 because the life of the refractory brick is improved.
Moreover, it is preferable that a ring-shaped or horseshoe-shaped water pipe for cooling the pipe is provided around the pipes of the bubblers 13, 14, 15 inside the refractory brick at the bottom of the melting tank 10 or outside the refractory brick.

Next, the molten glass manufacturing method of this invention is demonstrated.
In the molten glass manufacturing method of the present invention, the above-described molten glass manufacturing apparatus is used to perform bubbling from the middle-stream bubbling unit and bubbling from the upstream bubbling unit in the melting tank 10 of the molten glass manufacturing apparatus. A molten glass is produced while performing.
As described above, by carrying out the bubbling from the middle basin bubbling unit, without providing a step structure that affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass flow path, The formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10 is promoted, and the flow velocity of the upstream circulating flow 100 and the downstream circulation flow 101 are increased. Since it can control so that it may become a predetermined relationship, T ( _eta) is 1500-1760 degreeC and it is suitable for manufacture of an alkali-free glass with high homogeneity.
Moreover, homogenization of the molten glass G in the melting tank 10 can be promoted by carrying out the bubbling from the middle basin bubbling unit when the operation of the melting tank 10 is started or when the operating conditions of the melting tank are changed. Therefore, the time required for manufacturing the alkali-free glass can be shortened.

Specific examples of the alkali-free glass having T _η of 1500 to 1760 ° C. include alkali-free glass compositions 1 to 4 in which the oxide-based mass percentage display has the following composition.
Alkali-free glass composition 1
SiO ₂ : 50 to 73%, preferably 50 to 66%
Al ₂ O _3: 10.5~24%
B ₂ O _3: 0~12%
MgO: 0 to 10%, preferably 0 to 8%
CaO: 0 to 14.5%
SrO: 0 to 24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 8 to 29.5%, preferably 9 to 29.5%
ZrO ₂ : 0 to 5%
When considering the solubility with a high strain point, the alkali-free glass composition 2 is preferable.
SiO _2: 58~66%
Al ₂ O ₃ : 15-22%
B ₂ O _3: 5~12%
MgO: 0 to 8%
CaO: 0 to 9%
SrO: 3 to 12.5%
BaO: 0 to 2%
MgO + CaO + SrO + BaO: 9 to 18%
In particular, when considering solubility, the alkali-free glass composition 3 is preferable.
SiO _2: 50~61.5%
Al ₂ O _3: 10.5~18%
B ₂ O _3: 7~10%
MgO: 2-5%
CaO: 0 to 14.5%
SrO: 0 to 24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 16-29.5%
In particular, when considering a high strain point, it is preferable to use an alkali-free glass composition 4
SiO _2: 54~73%
Al ₂ O ₃ : 10.5 to 22.5%
B ₂ O ₃ : 0 to 5.5%
MgO: 0 to 10%
CaO: 0 to 9%
SrO: 0 to 16%
BaO: 0 to 2.5%
MgO + CaO + SrO + BaO: 8-26%

In the molten glass production method of the present invention, it is possible to set the average flow rate of the gases 18 and 19 supplied from the respective bubblers 14 and 15 constituting the middle-stream bubbling unit to 0.5 to 5.0 liters / minute. The formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) is promoted, and the flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 have a predetermined relationship. It is preferable when controlling so that it becomes.
Here, when the middle basin bubbling unit is configured by the first and second bubbler groups as in the dissolution tank 10 shown in FIGS. 1 and 2, the following (Control 1) and (Control 2) are performed. This promotes the formation of a circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10, and the flow rate of the upstream circulating flow 100 and the downstream circulating flow 101 This is preferable in controlling the flow rate so as to have a predetermined relationship. Thus, when the T _eta is producing molten glass from 1500 to 1760 ° C., can promote homogenization of molten glass, it is possible to obtain high homogeneity quality molten glass.

(Control 1)
The average flow rate V ₂ of the gas 19 from the bubbler 15 constituting the second bubbler group is made smaller than the average flow rate V ₁ of the gas 18 from the bubbler 14 constituting the first bubbler group.
(Control 2)
The ambient temperature T ₂ above the second bubbler 15 is set lower than the ambient temperature T ₁ above the first bubbler 14.

When (Control 1) is carried out, the V ₁ is preferably 0.5 to 20 liters / minute, more preferably 0.7 to 5 liters / minute, and 0.9 to 3 liters / minute. More preferably, it is particularly preferably 1.8 to 2.6 liters / minute. The V ₂ is preferably 0.3 to 19.8 liters / minute, more preferably 0.4 to 4.8 liters / minute, and 0.5 to 2 liters / minute. Is more preferable, and 0.9 to 2.0 liter / min is particularly preferable.
Further, V ₁ −V ₂ ≧ 0.2 liter / min is preferable, V ₁ −V ₂ ≧ 0.4 liter / min is more preferable, V ₁ −V ₂ ≧ 0.6 liter / min is further preferable, V ₁₋ V ₂ ≧ 1.0 liter / min is particularly preferred.

When carrying out (control 2), it is preferable that the T ₁ is a 1,590 to 1710 ° C., and more preferably from 1,600 to 1695 ° C.. Further, it is preferable that the T ₂ is 1570-1690 ° C., and more preferably 1580-1675 ° C..
Further, T ₁ -T ₂ is preferably 10~35 ℃, T ₁ -T ₂ is more preferably 15 to 30 ° C., more preferably 19 to 26 ° C..

T ₁ and T ₂ can be measured by the following method.
(Measurement position)
T ₁ : An intermediate position between the burner 16 closest to the upstream side of the bubbler 14 constituting the first bubbler group and the latest burner 16 positioned further upstream than the burner 16.
T ₂ : Intermediate position between the burner 16 closest to the downstream side of the bubbler 15 constituting the second bubbler group and the burner 16 closest to the downstream side of the bubbler.
(Measuring method)
From the observation window provided on the side surface of the dissolution tank, the inner wall surface temperature of the facing side surface is measured with a radiation thermometer (for example, CHINO IR-AH3SU (measurement wavelength: 0.65 μm, ε = 1.0)). taking measurement.

In the molten glass production method of the present invention, when the average flow rate of the gas 17 supplied from each bubbler 13 constituting the upstream region bubbling unit is 0.1 to 5.0 liters / minute, the operation of the melting tank 10 is started. In addition, it is preferable because the homogenization of the molten glass G in the melting tank 10 can always be promoted, including when the operating conditions of the melting tank 10 are changed.
Here, the average flow rate of the gas 17 supplied from each bubbler 13 constituting the upstream region bubbling unit is the upstream region bubbling unit at the start of operation of the dissolution tank 10 or when the operation conditions of the dissolution tank 10 are changed. Can be changed depending on the situation in which the homogenization of the molten glass G in the melting tank 10 is more demanded by bubbling and the normal operation of the melting tank 10. For example, when the operation of the dissolution tank 10 is started or when the operation conditions of the dissolution tank 10 are changed, the average flow rate of the gas 17 supplied from each bubbler 13 constituting the upstream region bubbling unit is 0.5 to 3.0. Liters / minute, preferably 1.0 to 2.0 liters / minute, and the average flow rate of the gas 17 supplied from each bubbler 13 constituting the upstream bubbling unit during the normal operation of the dissolution tank 10 is 0.1 to 1. It is preferably 0 liter / minute, preferably 0.2 to 0.5 liter / minute. The normal operation of the dissolution tank 10 where, for example, when the glass composition containing B ₂ O ₃ is, ± 1% are B ₂ O ₃ in mass percentage based on oxides with respect to the target composition, preferably It means a state of ± 0.5%, more preferably ± 0.3%.

In the molten glass production method of the present invention, when the average flow velocity of the upstream circulation flow 100 is F ₁ [m / hour] and the average flow velocity of the downstream circulation flow 101 is F ₂ [m / hour], F ₁ = 5 to 20 m / time is preferably controlled such that F ₂ = 0.5~7m / time. Thus, when the T _eta is producing molten glass from 1500 to 1760 ° C., can promote homogenization of molten glass, it is possible to obtain high homogeneity quality molten glass.
It is more preferable to control such that F ₁ = 8 to 15 m / hour and F ₂ = _{1 to 4} m / hour.
F ₁ and F ₂ can be measured by the following method.
(Measurement position)
F _1: distance from the upstream end of the molten glass flow path at 0.30L _F ~0.34L _F, near the center in the width direction of the molten glass flow path.
F _2: distance from the downstream end of the molten glass flow path at 0.22L _F ~0.30L _F, near the center in the width direction of the molten glass flow path.
(Measuring method)
Video of the flow of bubbles on the surface of the molten glass is taken, and the moving time with respect to the moving distance of the bubbles is measured to obtain the flow velocity. Repeat this procedure 2-3 times to determine the average flow rate.

Next, the plate glass manufacturing method of the present invention will be described.
In the plate glass manufacturing method of the present invention, the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into a plate glass. As a means for forming molten glass into plate glass, various forming methods such as a float method and a downdraw method can be used. If T _eta is a glass of 1,500 to 1,760 ° C., a float method is particularly preferable.
In the plate glass manufacturing method of the present invention, before the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into plate glass, bubbles in the molten glass may be degassed by vacuum degassing.
In the plate glass manufacturing method of the present invention, since the molten glass having high homogeneity obtained by the molten glass manufacturing method of the present invention is formed into a plate glass, a plate glass having high homogeneity and high transparency can be obtained.
The plate glass production apparatus of the present invention can be applied to the production of plate glass for various uses. However, since a plate glass having high homogeneity and high transparency can be obtained, the homogeneity of the glass substrate for FPD can be obtained. It is particularly preferable to apply it to the production of plate glass for applications in which the demands of these are extremely strict.

A glass raw material is introduced into the charging port of the melting tank 10 shown in FIGS. 1 and 2 so as to have a desired composition, and T _η is 1500 to 1760 ° C. Non-alkali glass. 1-4 are produced. The dimensions of each part of the dissolution tank 10 shown in FIGS.
Molten glass flow path length L _F : 16 to 25 m
Width W of molten glass channel: 5.5-9m
Distance from upstream end of molten glass flow path to each bubbler 13 constituting upstream bubbling unit: 0.1 L _F
Distance from the center in the width direction of the molten glass flow path to each bubbler 13 constituting the upstream bubbling unit: 0.5 W
Distance from the upstream end of the molten glass flow path to each of the bubblers 14 constituting the first bubbler group: 0.43L _{F to} 0.46L _F
Distance from the downstream end of the molten glass flow path to each bubbler 15 constituting the second bubbler group: 0.47L _{F to} 0.54L _F
Distance L _P between each bubbler 14 constituting the first bubbler group and each bubbler 15 constituting the second bubbler group: 600 to 800 mm
Pitch p between each bubbler 14 constituting the first bubbler group: 400 to 700 mm
Pitch p between each bubbler 15 constituting the second bubbler group: 400 to 700 mm
The distance from the upstream end of the molten glass channel to the burner 16 located on the most upstream side in the molten glass channel direction in the melting tank is 0.15 L _F
Distance L _B1 between the bubbler 14 constituting the first bubbler group and the burner 16 closest to the upstream side of the bubbler 14 in the flow direction of the molten glass in the melting tank: 500-1500 mm
Distance L _B2 between the bubbler 15 constituting the second bubbler group and the burner 16 closest to the downstream side of the bubbler 15 in the flow direction of the molten glass in the melting tank: 1000 to 2000 mm
L _B2 -L _B1 ≧ 500mm
Distance between individual burners 16 in the flow direction of the molten glass in the melting tank: 800 to 2400 mm
The average flow rate of the gas 17 from the bubbler 13 constituting the upstream bubbling unit is adjusted to 0.25 to 0.5 liter / min.
The average flow rate V ₁ of the gas 18 from the bubbler 14 constituting the first bubbler group, and the average flow rate V ₂ of the gas 19 from the bubbler 15 constituting the second bubbler group is adjusted to be the following conditions .
V ₁ : 1.8 to 2.6 liters / minute V ₂ : 0.9 to 2.0 liters / minute V ₁ −V ₂ ≧ 0.6 liters / minute By the combustion in the burner 16, the first bubbler group the atmosphere above the temperature T ₁ of the bubbler 14 of the, and, ambient temperature T ₂ above the bubbler 15 constituting the second bubbler group is held in the following conditions. T ₁ and T ₂ are measured by the method described above.
T ₁ : 1590 to 1710 ° C.
T ₂ : 1580-1675 ° C
T ₁ -T _2: 10~35 ℃
At the start of the operation of the melting tank 10, the time required for homogenization of the molten glass in the melting tank 10 is shortened by carrying out the bubbling from the bubbler 13 constituting the upstream bubbling unit.
The average flow rate F ₂ in average flow rate F ₁ and the downstream circulation flow 101 of the upstream circulation flow 100 in the dissolution tank 10 is measured by the method described above. The results are as follows.
F ₁ = 8 to 15 m / hour F ₂ = _{1 to 4} m / hour By carrying out under the above conditions, a high-quality alkali-free glass having a high homogeneity at a T _η of 1500 to 1760 ° C. is produced. The time required for the production of alkali glass can be shortened.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2011-277287 filed on Dec. 19, 2011, the contents of which are incorporated herein by reference.

According to the molten glass manufacturing apparatus and the molten glass manufacturing method of the present invention, homogenization of the molten glass can be promoted even when the operation of the melting tank is started or when the operating conditions of the melting tank are changed. It is suitable for production of high-quality, high-quality alkali-free glass, and the time required for production of the alkali-free glass can be shortened.
Since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and high transparency, it is suitable for manufacture of the board | substrate for FPD.

10: Dissolution tank 11: Input port 12: Discharge port 13: Bubbler (upstream bubbling unit)
14: Bubbler (middle basin bubbling unit, first bubbler group)
15: Bubbler (middle basin bubbling unit, second bubbler group)
16: Burner 17: Gas from bubbler (upstream bubbling unit) 18: Gas from bubbler (middle basin bubbling unit, first bubbler group) 19: From bubbler (middle basin bubbling unit, second bubbler group) Gas 20: Downstream conduit 100: Upstream circulating flow 101: Downstream circulating flow

Claims (12)

A molten glass production apparatus having a melting tank for melting glass raw materials,
The dissolution tank has a burner for heating the upper space of the dissolution tank,
When the length of molten glass flow path of the melting tank and L _F, and midstream bubbling unit is provided at a position where the distance from the upstream side of the dissolution tank becomes 0.4L _F ~0.6L _F , and the upstream region bubbling unit provided at a position where the distance from the upstream side of the dissolution tank becomes 0.05L _F ~0.2L _F,
The midstream bubbling unit is composed of a bubbler group in which a plurality of bubblers are provided in the vicinity of the bottom surface of the melting tank over the width direction of the molten glass flow path of the melting tank,
The upstream region bubbling unit is composed of a plurality of bubblers provided in parallel in the width direction of the molten glass flow path of the melting tank in the vicinity of the bottom surface of the melting tank,
The upstream glass bubbling unit includes at least a pair of bubblers provided at positions symmetrical to the center in the width direction of the molten glass flow path.   When the width of the molten glass flow path of the melting tank is W, each bubbler constituting the upstream region bubbling unit has a distance from the center in the width direction of the molten glass flow path of 0.25 W or more, and The molten glass manufacturing apparatus of Claim 1 provided in the position where the distance from the side wall of a melting tank satisfy | fills 400 mm or more.   The melter according to claim 1 or 2, wherein each bubbler constituting the upstream region bubbling unit is provided further upstream than a burner located most upstream in the length direction of the molten glass flow path. Glass manufacturing equipment.   The molten glass manufacturing apparatus according to any one of claims 1 to 3, wherein the midstream bubbling unit includes a plurality of bubbler groups whose positions in the length direction of the molten glass channel are different from each other.   5. Each of the bubblers constituting the midstream bubbling unit and the upstream bubbling unit is made of platinum or a platinum alloy, and the gas supplied from each of the bubblers is a gas not containing oxygen. The molten glass manufacturing apparatus as described in any one of Claims.   Using the molten glass production apparatus according to any one of claims 1 to 5, a molten glass is produced while supplying a gas from each bubbler constituting the midstream bubbling unit and the upstream bubbling unit. Glass manufacturing method. The molten glass manufacturing method of Claim 6 which manufactures the molten glass whose temperature T ( _eta ) from which glass viscosity (eta) becomes 10 < ² > [dPa * s] is 1500-1760 degreeC.   The average flow rate of the gas supplied from each bubbler constituting the midstream bubbling unit is 0.5 to 5.0 liters / minute, and the average flow rate of the gas supplied from each bubbler constituting the upstream bubbling unit is 0. The molten glass manufacturing method of Claim 6 or 7 set to 1-5.0 liters / min.   The plate glass manufacturing method which shape | molds the molten glass obtained by the molten glass manufacturing method as described in any one of Claims 6-8 to plate glass. Molten glass is a mass percentage display based on oxide,
SiO _2: 50~73%
Al ₂ O _3: 10.5~24%
B ₂ O _3: 0~12%
MgO: 0 to 10%
CaO: 0 to 14.5%
SrO: 0 to 24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 8 to 29.5%
ZrO ₂ : 0 to 5%
The molten glass manufacturing apparatus according to any one of claims 1 to 5, wherein the glass-containing alkali-free glass is contained. Molten glass is a mass percentage display based on oxide,
SiO _2: 50~73%
Al ₂ O _3: 10.5~24%
B ₂ O _3: 0~12%
MgO: 0 to 10%
CaO: 0 to 14.5%
SrO: 0 to 24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 8 to 29.5%
ZrO ₂ : 0 to 5%
The method for producing molten glass according to any one of claims 6 to 8, wherein the glass is a non-alkali glass. Molten glass is a mass percentage display based on oxide,
SiO _2: 50~73%
Al ₂ O _3: 10.5~24%
B ₂ O _3: 0~12%
MgO: 0 to 10%
CaO: 0 to 14.5%
SrO: 0 to 24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 8 to 29.5%
ZrO ₂ : 0 to 5%
The plate glass manufacturing method according to claim 9, wherein the glass is non-alkali glass.

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