CN112041277A

CN112041277A - Method for manufacturing glass article

Info

Publication number: CN112041277A
Application number: CN201980029112.0A
Authority: CN
Inventors: 长谷川彻; 爱陆朗
Original assignee: Nippon Electric Glass Co Ltd
Current assignee: Nippon Electric Glass Co Ltd
Priority date: 2018-06-27
Filing date: 2019-06-04
Publication date: 2020-12-04
Anticipated expiration: 2039-06-04
Also published as: KR20210023801A; WO2020003915A1; JP7198423B2; TWI807047B; JP2020001953A; TW202010715A; CN112041277B

Abstract

A method of manufacturing a glass article, comprising: a continuous production step in which a glass raw material (4) is continuously supplied to a molten glass (2) stored in a furnace (1), the raw material (4) is melted to continuously produce new molten glass (2), and the molten glass (2) is caused to flow out of the furnace (1) through a pipe (5) having an inner circumferential surface (5a) made of platinum or a platinum alloy; and a starting step of starting the furnace (1) to a state in which the continuous production step can be executed, wherein the starting step includes a temperature raising step of raising the temperature in the furnace (1) from a normal temperature by the burners (7, 8), and in the temperature raising step, the burners (7, 8) heat the furnace (1) while reducing contact between the ambient gas in the furnace and the inner circumferential surface (5a) of the pipe (5).

Description

Method for manufacturing glass article

Technical Field

The present invention relates to a method for producing a glass article, including a step of continuously producing molten glass, which is a source of the glass article, using a glass melting furnace, and a step of starting the furnace to a state in which the step can be performed.

Background

As is well known, glass articles represented by glass plates, glass tubes, glass fibers, and the like are manufactured by forming molten glass, which is produced by melting glass raw materials, into a predetermined shape. Here, patent document 1 discloses an example of a method for continuously producing molten glass using a glass melting furnace.

In the method disclosed in this document, while continuously supplying a glass raw material to a molten glass stored in a glass melting furnace, the glass raw material is melted to continuously produce a new molten glass, and the molten glass is allowed to flow out of the furnace through a flow-out passage (in this document, a furnace throat). The inner circumferential surface of the outflow passage is usually made of platinum or a platinum alloy.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-183031

Disclosure of Invention

Problems to be solved by the invention

However, when operating a glass melting furnace, the furnace needs to be started up to a state in which molten glass can be continuously produced. In order to raise the temperature in the furnace from room temperature at the start-up of the furnace, there are often used an air burner for mixing and burning a gaseous fuel such as natural gas with air, and an oxygen burner for mixing and burning a gaseous fuel with oxygen. When the temperature in the furnace rises to a temperature at which the glass raw material can be melted by heating with these burners, the supply of the glass raw material into the furnace is started. In conjunction with this, the glass raw material is melted, and the molten glass is stored in the furnace.

However, the glass melting furnace of the above-described type has the following problems in starting up the furnace.

That is, when an air burner or an oxygen burner is used to raise the temperature in the glass melting furnace, air and oxygen are continuously supplied into the furnace, and accordingly, the ambient gas in the furnace containing oxygen inevitably flows into the outflow passage. As a result, platinum or a platinum alloy constituting the inner peripheral surface of the outflow passage is oxidized or volatilized.

In view of the above, the technical object of the present invention is to suppress oxidation and volatilization of platinum and platinum alloys constituting the inner circumferential surface of the outflow passage of molten glass as much as possible when the furnace is started up by raising the temperature in the glass melting furnace by heating with the burner when producing glass articles.

Means for solving the problems

The present invention for solving the above-described problems provides a method for manufacturing a glass article, including: a continuous production step of continuously producing new molten glass by melting a glass raw material while continuously supplying the glass raw material to the molten glass stored in the glass melting furnace, and allowing the molten glass to flow out of the glass melting furnace through an outflow passage having an inner peripheral surface made of platinum or a platinum alloy; and a starting step of starting the glass melting furnace to a state in which the continuous production step can be executed, wherein the starting step includes a temperature raising step of raising a temperature in the glass melting furnace from a normal temperature by a burner and a raw material supply starting step of starting supply of a glass raw material into the glass melting furnace, and in the temperature raising step, the burner heats the glass melting furnace while contact between an ambient gas in the glass melting furnace and an inner peripheral surface of the outflow passage is reduced.

According to the method, in the temperature raising step, the temperature in the glass melting furnace is raised from the normal temperature by heating with the burner while reducing contact between the ambient gas in the glass melting furnace and the inner peripheral surface of the outflow passage. Thus, even when the ambient gas in the furnace containing oxygen fed into the furnace along with the use of the burner flows into the outflow passage or attempts to flow into the outflow passage, oxidation and volatilization of platinum or a platinum alloy constituting the inner peripheral surface of the outflow passage can be suppressed as much as possible.

In the above method, it is preferable that the shield prevents the ambient gas in the glass melting furnace from contacting the inner peripheral surface of the outflow passage.

The contact between the ambient gas in the glass melting furnace and the inner peripheral surface of the outflow passage can be stably reduced by preventing the ambient gas in the glass melting furnace from contacting the inner peripheral surface of the outflow passage by the shield.

In the above method, it is preferable to use a glass member as the shielding member.

The following effects can be obtained by preventing the ambient gas in the furnace from contacting the inner peripheral surface of the outflow passage with the glass material. That is, a member other than glass (for example, a metal member, a refractory material, or the like) may be used as the mask, but in this case, an operation of removing the mask occurs. Further, the shield may be mixed into the molten glass, which may cause a problem. When a glass material is used, the glass material is not melted for a long time to become molten glass with an increase in temperature in the furnace, and is conveyed to the downstream process together with the molten glass melted from the glass raw material. Therefore, if the glass material is used as the shield, the work of removing the shield is not required, and the risk of the shield mixing into the molten glass and causing troubles can be eliminated.

In the above method, it is preferable to use a glass plate covering the opening at the upstream end of the outflow passage as the glass member.

In this way, the inflow of the ambient gas in the furnace containing oxygen into the outflow passage can be reliably avoided by the glass plate covering the opening at the upstream end of the outflow passage. This is more advantageous in that oxidation and volatilization of platinum or a platinum alloy constituting the inner circumferential surface of the outflow passage are suppressed as much as possible.

In the above method, the composition of the glass material is preferably the same as that of the molten glass.

In this way, the composition of the molten glass can be prevented from being changed by the glass material, and therefore, the use of the molten glass is advantageous.

In the above method, it is preferable that the glass melting furnace includes an electrode movable between an entry position into the furnace and a retreat position retreated from the furnace, and in the continuous forming step, the electrode located at the entry position is used to perform energization heating, and in the temperature raising step, the burner is used to perform heating in a state where the tip of the electrode located at the retreat position is covered with the cover member to prevent contact between the electrode and the ambient gas in the glass melting furnace.

In this way, by covering the electrode with the cover member, contact between the electrode and the atmosphere in the furnace can be reduced, and the electrode can be protected from oxidation.

In the above method, the glass melting furnace may be a first glass melting furnace, the flow-out passage is a first flow-out passage, and the first glass melting furnace and the second glass melting furnace are connected by the first flow-out passage, the second glass melting furnace into which the molten glass having flowed out of the first glass melting furnace flows, a temperature raising step of raising the temperature in the second glass-melting furnace from room temperature by a burner is executed, in the temperature raising step in the second glass-melting furnace, in a state where the contact of the ambient gas in the second glass-melting furnace with the inner peripheral surface of the first outflow passage and the contact of the ambient gas in the second glass-melting furnace with the inner peripheral surface of the second outflow passage formed of platinum or a platinum alloy are prevented by the shield, the burner heats the glass melt, and the second outflow path is used for flowing out the molten glass to the outside of the second glass melting furnace.

In this way, oxidation and volatilization of platinum or a platinum alloy constituting the inner peripheral surface of the outflow passage (second outflow passage) can be suppressed as much as possible not only in the first glass melting furnace but also in the second glass melting furnace.

In the above method, it is preferable that the molten glass stored in the glass melting furnace is heated only by electric heating in the continuous forming step.

In this way, the ambient gas in the glass melting furnace can be dried as compared with the case of heating by the burner and the energization heating in combination. This makes it easy to prevent moisture in the atmosphere gas in the furnace from dissolving into the molten glass, and to reduce the β -OH value in the glass article to be produced. As a result, the degree of compaction at the time of heating the glass article can be reduced, and a glass article suitable for an alkali-free glass substrate for a display can be obtained.

Here, the "alkali-free glass" means a glass containing substantially no alkali component (alkali metal oxide), and specifically means a glass having an alkali component in a weight ratio of 3000ppm or less. The weight ratio of the alkali component is preferably 1000ppm or less, more preferably 500ppm or less, and most preferably 300ppm or less.

Effects of the invention

According to the present invention, in the production of a glass article, oxidation and volatilization of platinum or a platinum alloy constituting the inner peripheral surface of the outflow path of molten glass can be suppressed as much as possible when the furnace is started up by raising the temperature in the glass melting furnace by heating with the burner.

Drawings

Fig. 1 is a vertical cross-sectional side view showing a continuous forming step in a method for producing a glass article according to a first embodiment of the present invention.

Fig. 2 is a cross-sectional plan view showing a continuous forming step in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 3 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 4 is a perspective view showing a startup process in the method for manufacturing a glass article according to the first embodiment of the present invention.

Fig. 5 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 6 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 7 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 8 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 9 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the first embodiment of the present invention.

Fig. 10 is a vertical cross-sectional side view showing a startup process in the method for producing a glass article according to the second embodiment of the present invention.

Detailed Description

< first embodiment >

Hereinafter, a method for manufacturing a glass article according to a first embodiment of the present invention will be described with reference to the drawings.

Fig. 1 and 2 show a case where a continuous production process is performed in a glass melting furnace 1 (hereinafter, simply referred to as furnace 1).

In the continuous forming step, while the molten glass 2 stored in the furnace 1 is electrically heated by the electrode 3 while the temperature in the furnace 1 (molten glass) is maintained at the operating temperature (for example, 1450 to 1550 ℃), the glass raw materials 4 continuously supplied onto the surface 2a of the molten glass 2 are sequentially melted to continuously form new molten glass 2, and the molten glass 2 is caused to flow out of the furnace 1 through the pipe 5 serving as an outflow path (first outflow path). In the continuous forming step, the molten glass 2 is heated only by the energization and heating of the electrodes 3.

The molten glass 2 produced in the continuous production step is conveyed to a downstream step including a forming step and the like, and in the downstream step, a glass article (for example, a glass plate, a glass tube, a glass fiber or the like) is produced through a process of forming the molten glass 2 and the like.

The furnace 1 used in the present embodiment has a rectangular cross-sectional shape in plan view. The furnace 1 has: a front wall 1a located at an upstream end in a flow direction T of the glass raw material 4 in the furnace 1; a rear wall 1b at a downstream end; a pair of

side walls

1c, 1 d; a neck wall 1 e; and a bottom wall 1 f. These furnace walls 1a to 1f are each formed of a refractory (in the present embodiment, high zirconia electrically fused cast refractory brick).

A plurality of (three in the present embodiment) screw feeders 6 for supplying the glass raw material 4 into the furnace 1 are arranged in parallel on the front wall 1 a. Each screw feeder 6 is inserted into the opening 1aa formed in the front wall 1a without a gap. In addition, tin oxide is added as a fining agent to the glass raw material 4 supplied from the screw feeder 6.

Here, in the present embodiment, the screw feeder 6 is used for supplying the glass raw material 4, but a raw material feeder other than the screw feeder 6 may be used. As an example of the raw material feeder, a vibration feeder, a pusher, a felt feeder, or the like may be used. From the viewpoint of improving the sealing property in the furnace 1, it is preferable to use the screw feeder 6 or the vibrating feeder. In the present embodiment, a plurality of screw feeders 6 are used, but the number of screw feeders 6 may be only one.

A pipe 5 for flowing out the molten glass 2 is disposed on the rear wall 1 b. The inner circumferential surface 5a of the pipe 5 is made of platinum or a platinum alloy.

A burner pair 9 formed by a pair of one air burner 7 and one oxygen burner 8 is disposed on each of the

side walls

1c and 1d, and in the present embodiment, three pairs of burner pairs 9 are disposed on the side wall 1c and two pairs of burner pairs 9 are disposed on the side wall 1 d. In the present embodiment, the air burners 7 and the oxygen burners 8 are arranged in pairs, but the number of the air burners 7 and the number of the oxygen burners 8 may be different. The air burner 7 and the oxygen burner 8 may be disposed on the ceiling wall 1 e. In the execution of the continuous production process of the present embodiment, both the air burner 7 and the oxygen burner 8 are in the state of operation stoppage in each of the five pairs of burners 9 in total.

The air burner 7 is a burner that mixes and burns a gas fuel such as natural gas with air. In contrast, the oxygen burner 8 is a burner that mixes and burns a gas fuel with oxygen.

As shown by the two-dot chain lines in fig. 2, the

burners

7 and 8 can inject

flames

7a and 8a from the side wall 1c (side wall 1d) toward the side wall 1d (side wall 1c) facing each other. The heating power of the oxygen burner 8 is larger than that of the air burner 7. On the other hand, the flame 7a injected from the air burner 7 is wider than the flame 8a injected from the oxygen burner 8 in a plan view. In the present embodiment, the air burner 7 can be removed from the side wall 1c (side wall 1d) in a state in which the operation is stopped. The oxygen burner 8 may be detachable from the side wall 1c (side wall 1d) in a state in which the operation is stopped.

The electrode 3 disposed on the bottom wall 1f is formed in a rod shape. The electrode 3 is movable between an entering position (position where the electrode 3 is located in fig. 1) where it enters the furnace 1 from the bottom wall 1f and a retreating position (position where the electrode 3 is located in fig. 3 mentioned later) where it retreats from the inside of the furnace 1. The electrode 3 is made of molybdenum, for example.

During the continuous forming step, the molten glass 2 is heated by the electrode 3 located at the entry position and in a state immersed in the molten glass 2 in the furnace 1. By adjusting the voltage applied to the electrode 3, the energy generated by the electrode 3 (the thermal energy applied to the molten glass 2) can be adjusted. As the electrode 3 heats the molten glass 2, the glass material 4 on the surface 2a of the molten glass 2 is indirectly heated and melted. Thereby, new molten glass 2 is sequentially produced.

Here, in the present embodiment, the molten glass 2 is heated by the rod-shaped electrode 3, but the molten glass 2 may be heated by a plate-shaped electrode or a block-shaped electrode arranged on each of the pair of

side walls

1c and 1d in addition to the rod-shaped electrode 3 or in place of the rod-shaped electrode 3.

In the present embodiment, when the furnace 1 is started up to a state in which the above-described continuous production process can be performed, the following start-up process is performed.

In the start-up step, a first temperature raising step (fig. 3) of raising the temperature in the furnace 1 from a normal temperature (not particularly cold or hot, for example, 20 ℃ ± 15 ℃) by the air burner 7, a second temperature raising step (fig. 5) of raising the temperature in the furnace 1 by the oxygen burner 8, a raw material supply starting step (fig. 6) of starting supply of the glass raw material 4 into the furnace 1, and an energization heating starting step (fig. 8) of starting energization heating of the molten glass 2 stored by melting the glass raw material 4 are performed. In the present embodiment, the temperature raising step is constituted by both the first temperature raising step and the second temperature raising step.

First, as a preparation for executing the startup process, before the first temperature raising step is started, as shown in fig. 3, the first glass plate 10 (cover member) is placed on the bottom wall 1f of the furnace 1 with the electrode 3 positioned at the retracted position. Since the first glass plate 10 is positioned directly above the electrode 3, the front end (upper end) of the electrode 3 is covered with the first glass plate 10. In this way, the electrode 3 is protected by the first glass plate 10. The state in which the electrode 3 is covered with the first glass plate 10 continues until the first glass plate 10 is melted as the temperature in the furnace 1 rises. Thus, the oxygen-containing ambient gas in the furnace 1 is prevented from contacting the electrode 3 during the period from the start of the first temperature increasing step to the melting of the first glass plate 10, and the oxidation of the electrode 3 is avoided as much as possible. The space formed between the first glass plate 10 and the electrode 3 is filled with a plurality of pieces of glass (not shown) formed in a block shape.

Here, in the present embodiment, when the electrode 3 is separated from the inside of the furnace 1, the tip of the electrode 3 is covered with the first glass plate 10, but the present invention is not limited thereto. Instead of the first glass plate 10, the front end of the electrode 3 may be covered with, for example, cullet. Of the first glass plate 10 and cullet, a glass plate and cullet composed of glass of the same composition system as the molten glass 2 produced by melting the glass raw material 4 are preferably used, and a glass plate and cullet composed of the same composition as the molten glass 2 are more preferably used.

Before the first temperature raising step is started, the opening 5ba of the upstream end portion 5b of the tube 5 is covered with the second glass plate 11 and the third glass plate 12 as glass members. In this way, the interior of the tube 5 is separated from the interior of the furnace 1 by the two

glass plates

11, 12. The state in which the inside of the duct 5 and the inside of the furnace 1 are partitioned continues until the

glass plates

11 and 12 are melted as the temperature in the furnace 1 rises. Thus, during the period from the start of the first temperature raising step to the melting of both

glass sheets

11 and 12, the gas is prevented from going between the inside of the furnace 1 and the inside of the tube 5, and the ambient gas containing oxygen in the furnace 1 is prevented from coming into contact with the inner peripheral surface 5a of the tube 5. In this way, oxidation of platinum constituting the inner circumferential surface 5a of the tube 5 is avoided as much as possible. When the molten glass 2 is alkali-free glass, it is preferable to use a glass plate made of alkali-free glass as the

glass plates

11 and 12.

Hereinafter, a specific embodiment of providing the second glass plate 11 and the third glass plate 12 will be described with reference to fig. 4. In the present embodiment, a case where the flow path cross section of the tube 5 is rectangular will be described as an example. Of course, the present invention can be applied to a case where the cross section of the flow path of the tube 5 is not rectangular, but circular, elliptical, or polygonal, for example.

As shown in fig. 4, one second glass plate 11 is provided, and two third glass plates 12 are provided so as to sandwich the second glass plate 11. In the present embodiment, both

glass plates

11, 12 have a rectangular shape.

The second glass plate 11 is provided in an upright state at the upstream end 5b of the tube 5 (the rear wall 1b of the furnace 1). The principal surface (front and back surfaces) of the second glass plate 11 is inclined with respect to the vertical line. The width dimension (the dimension of the width in the horizontal direction) of the second glass plate 11 is the same as the width dimension of the tube 5. The upper edge portion of the second glass plate 11 is located above the upper portion of the upstream end portion 5 b. On the other hand, the lower edge of the second glass plate 11 is in contact with the bottom wall 1f of the furnace 1.

The two third glass plates 12 are respectively provided in a substantially upright posture in a state in which the principal surfaces thereof are upright so as to be in contact with the width direction end surfaces of the second glass plate 11. The upper edge portions of the third glass plates 12 are located above the upper portion of the upstream end portion 5 b. On the other hand, the lower edge of the third glass plate 12 is in contact with the bottom wall 1f of the furnace 1. One of a pair of side portions extending in the vertical direction of the third glass sheet 12 is in contact with the rear wall 1b of the furnace 1.

Although not shown, it is preferable that the gap extending from the inside of the furnace 1 into the pipe 5, including the gap formed between the end face in the width direction of the second glass plate 11 and the main face of the third glass plate 12, be closed by a glass sheet, cullet, or the like, which is a glass material. Since these gaps are required to be as small as possible, the glass raw material 4 may be used for blocking, but a glass material is preferably used from the viewpoint of avoiding a risk that a part of the components of the raw material 4 volatilizes before melting. The surface shapes of the second glass plate 11 and the third glass plate 12 may be, for example, trapezoidal or triangular, instead of being rectangular, or glass plates having different surface shapes may be used in combination.

In the present embodiment, the outer peripheral surface of the upstream end portion 5b is not exposed to the atmosphere in the furnace 1, but is in contact with the rear wall 1b, but the outer peripheral surface of the upstream end portion 5b may be exposed to the atmosphere in the furnace 1. In this case, all the portions (portions made of platinum or a platinum alloy) of the pipe 5 that come into contact with the molten glass 2 during the execution of the continuous forming step, including the outer peripheral surface of the upstream end portion 5b, may be covered with cullet, a glass plate, a glass sheet, the glass material 4, and the like. For example, the upper surface of the outer peripheral surface of the upstream end portion 5b may be covered with glass plates, and the side surfaces of the outer peripheral surface of the upstream end portion 5b may be covered with the two third glass plates 12. The inner circumferential surface 5a of the tube 5 may be covered with the glass material 4 filled in the tube 5.

Here, in the present embodiment, before the first temperature raising step is started, the tip of the electrode 3 is covered with the first glass plate 10, and the opening 5ba of the upstream end portion 5b is covered with the second glass plate 11 and the third glass plate 12, but the present invention is not limited thereto, and these steps may be performed at the start of the first temperature raising step.

As described above, when the preparation for executing the startup process is completed, next, as shown in fig. 3, the air burner 7 is operated to inject the flame 7a, thereby starting the first temperature raising step. In the present embodiment, at the start of the first temperature raising step, the glass sheets and cullet blocking the gaps between the first to

third glass sheets

10, 11, 12 and the two

glass sheets

11, 12 are removed without starting the supply of the glass material 4 into the furnace 1, and the molten glass 2 and the glass material 4 are not present in the furnace 1.

After the first temperature raising step is started, when the temperature in the furnace 1 (the ambient air temperature of the ceiling wall 1 e) rises to any temperature in the range of 700 to 900 ℃, as shown in fig. 5, switching is performed from the first temperature raising step to the second temperature raising step. For example, the operation of the air burner 7 is sequentially stopped, and the operation of the oxygen burner 8 is sequentially started. When the operation of the first oxygen burner 8 is started, the second temperature raising step is started.

After the switching from the first temperature raising step to the second temperature raising step, when the temperature in the furnace 1 rises to a temperature at which the glass raw material 4 can be melted (hereinafter, referred to as a temperature at which the glass raw material can be melted), as shown in fig. 6, the raw material supply starting step is performed by operating the screw feeder 6 and starting the supply of the glass raw material 4 into the furnace 1. The glass raw material 4 may be a part or the whole of cullet.

In the raw material supply starting step, the temperature in the furnace 1 may be increased to a temperature at which the raw material can be melted, and the switching from the first temperature increasing step to the second temperature increasing step may be completed at the same time. On the other hand, the raw material supply starting step may be performed at any time point before the temperature in the furnace 1 rises to a temperature at which melting is possible. However, from the viewpoint of avoiding the risk that components contained in the glass raw material 4 volatilize and disappear before the melting of the raw material 4, it is preferable to perform the raw material supply starting step after the temperature in the furnace 1 rises to a temperature at which the melting is possible.

After the raw material supply starting step, as shown in fig. 7, the glass raw materials 4 supplied into the furnace 1 are sequentially melted, and the molten glass 2 is stored in the furnace 1. Thereby, the height position of the surface 2a of the molten glass 2 gradually rises in the furnace 1. As shown by the two-dot chain line in fig. 7, the first glass plate 10 that partitions the interior of the furnace 1 from the electrode 3, the second glass plate 11 that partitions the interior of the furnace 1 from the interior of the tube 5, and the third glass plate 12 are melted in this order as the temperature in the furnace 1 increases.

Then, after the height position of the surface 2a of the molten glass 2 reaches a predetermined reference position, the electrode 3 is moved from the retreat position to the retreat position as shown in fig. 8. Then, an energization heating start step is performed by applying a voltage to the electrode 3. The temperature in the furnace 1 (molten glass) at this time is, for example, in the range of 1300 ℃ to 1600 ℃.

Thereafter, as shown in fig. 9, when the height position of the surface 2a of the molten glass 2 reaches the position at the time of performing the continuous forming process and the temperature in the furnace 1 is substantially uniform at the operating temperature, the operation of the oxygen burners 8 is sequentially stopped in order to maintain the temperature in the furnace 1. When the operation of all the oxygen burners 8 is stopped, the startup process is completed. Then, the continuous production process is started in the furnace 1.

Hereinafter, the main operation and effect of the method for manufacturing a glass article according to the embodiment of the present invention will be described.

In the method for producing a glass article according to the first embodiment, in the first temperature raising step and the second temperature raising step, the ambient gas in the furnace 1 is heated by the air burner 7 or the oxygen burner 8 while the contact with the inner peripheral surface 5a of the pipe 5 is prevented by the

glass plates

11 and 12, and the temperature in the furnace 1 is raised from the normal temperature. This can prevent the ambient gas in the furnace 1 containing the oxygen fed into the furnace 1 from flowing into the pipe 5 as the

burners

7 and 8 are used. As a result, oxidation or volatilization of platinum or a platinum alloy constituting the inner circumferential surface 5a of the tube 5 can be suppressed as much as possible.

< second embodiment >

A method for manufacturing a glass article according to a second embodiment of the present invention will be described below with reference to fig. 10. In the description of the second embodiment, substantially the same elements as those described in the above-described first embodiment are denoted by the same reference numerals, and overlapping description is omitted, and only differences from the first embodiment will be described.

The second embodiment is different from the first embodiment described above in that the furnace 1 is a first glass melting furnace 13 (hereinafter referred to as a first furnace 13) and the pipe 5 is a first pipe 14, and the first furnace 13 is connected to a second glass melting furnace 15 (hereinafter referred to as a second furnace 15) into which the molten glass 2 flowing out from the first furnace 13 flows via the first pipe 14. The second furnace 15 has the same structure as the first furnace 13, except that it does not have the screw feeder 6. The first pipe 14 of the present embodiment is disposed in a posture in which the longitudinal direction thereof is horizontal, but may be disposed in the following posture: the longitudinal direction is inclined so as to become higher as the distance from the first furnace 13 increases. In the present embodiment, the bottom wall 1f of the first furnace 13 and the bottom wall 1f of the second furnace 15 are at the same height, but the bottom wall 1f of the second furnace 15 may be disposed at a position higher than the bottom wall 1f of the first furnace 13, or the bottom wall 1f of the second furnace 15 may be disposed at a position lower than the bottom wall 1f of the first furnace 13.

In the second furnace 15, a first temperature raising step and a second temperature raising step are also executed in which the temperature in the second furnace 15 is raised from the normal temperature by the air burner 7 or the oxygen burner 8. In the present embodiment, the first temperature raising step and the second temperature raising step of the second furnace 15 are started to be executed simultaneously with the execution of the first temperature raising step and the second temperature raising step in the first furnace 13, but the simultaneous start or the synchronous execution is not necessarily required, and a time lag may be somewhat caused. The first temperature raising step and the second temperature raising step in the second furnace 15 can be performed under the same conditions as those in the first temperature raising step and the second temperature raising step in the first furnace 13.

In the first temperature raising step and the second temperature raising step in the second furnace 15, the opening 5ca of the downstream side end portion 5c of the first pipe 14 may not be covered with a glass plate, but in order to further prevent the ambient gas in the second furnace 15 from coming into contact with the inner peripheral surface 5a of the first pipe 14, it is preferable to cover the opening 5ca of the downstream side end portion 5c of the first pipe 14 with the second glass plate 11 and the third glass plate 12 as glass members, as shown in fig. 10. The opening 5ca of the downstream end portion 5c is covered in the same manner as the opening 5ba of the upstream end portion 5 b.

In the first temperature increasing step and the second temperature increasing step in the second furnace 15, the ambient gas in the second furnace 15 is prevented from contacting the inner circumferential surface 5a of the second pipe 16 serving as a second outflow path for flowing the molten glass 2 out of the second furnace 15. For this purpose, the opening 5ba of the upstream-side end portion 5b of the second tube 16 is covered with the second glass plate 11 and the third glass plate 12 as glass members. The opening 5ba of the upstream side end portion 5b of the second tube 16 is covered in the same manner as the opening 5ba of the upstream side end portion 5b of the first tube 14.

The present invention is not limited to the configurations of the above embodiments, and is not limited to the above-described operational effects. The present invention can be variously modified within a scope not departing from the gist of the present invention.

In the above-described embodiment, the molten glass is continuously produced only by heating the electrode 3 in the continuous production step, but the present invention is not limited thereto, and the heating by the

burners

7 and 8 may be used in combination. In the continuous production step in the case where the glass melting furnace is constituted by the first furnace 13 and the second furnace 15 as in the second embodiment, the heating by the electrode 3 and the heating by the

burners

7 and 8 may be used in combination in the first furnace 13, and only the heating by the

burners

7 and 8 may be used in the second furnace 15. When the

burners

7 and 8 are used for heating in the continuous production step, it is preferable to use the oxygen burner 8. From the viewpoint of reducing the β -OH value of the glass article to be produced, it is preferable to use a single melting furnace 1 and continuously produce molten glass only by heating the electrode 3 in the continuous production step, as in the first embodiment.

Description of reference numerals:

1 glass melting furnace

2 molten glass

4 glass raw material

5 tube

5a inner peripheral surface

5b upstream end portion

5ba opening

7 air burner

8 oxygen burner

11 second glass plate

12 third glass plate

13 first glass melting furnace

14 first pipe

15 second glass melting furnace

16 second tube.

Claims

1. A method of manufacturing a glass article, comprising: a continuous production step of continuously producing new molten glass by melting a glass raw material stored in a glass melting furnace while continuously supplying the glass raw material to the molten glass, and allowing the molten glass to flow out of the glass melting furnace through an outflow passage having an inner circumferential surface made of platinum or a platinum alloy; and a start-up step of starting up the glass melting furnace to a state in which the continuous production step can be executed,

the method for manufacturing a glass article is characterized in that,

the start-up step includes a temperature raising step of raising the temperature in the glass melting furnace from a normal temperature by a burner and a raw material supply starting step of starting supply of the glass raw material into the glass melting furnace,

in the temperature increasing step, the burner heats the glass melting furnace while reducing contact between the ambient gas in the glass melting furnace and the inner circumferential surface of the outflow passage.

2. The method for manufacturing a glass article according to claim 1,

the contact between the ambient gas in the glass melting furnace and the inner peripheral surface of the outflow passage is prevented by a shield.

3. The method for manufacturing a glass article according to claim 2,

a glass piece is used as the shield.

4. The method for manufacturing a glass article according to claim 3,

a glass plate covering an opening of an upstream end portion of the outflow passage is used as the glass member.

5. The method for manufacturing a glass article according to claim 3 or 4,

the composition of the glass piece is the same as the composition of the molten glass.

6. The method for producing a glass article according to any one of claims 1 to 5,

the glass melting furnace is provided with an electrode which can move between an entering position entering the furnace and a retreating position retreating from the furnace,

in the continuous production step, the electrode located at the entry position is used to perform energization heating,

in the temperature raising step, the burner heats the glass melting furnace while preventing the contact between the electrode and the ambient gas in the glass melting furnace by covering the tip of the electrode located at the retracted position with a cover member.

7. The method for producing a glass article according to any one of claims 1 to 6,

the glass melting furnace is set as a first glass melting furnace, and the outflow passage is set as a first outflow passage,

the first glass melting furnace and a second glass melting furnace into which molten glass flowing out from the first glass melting furnace flows are connected by the first outflow passage,

in the second glass-melting furnace, a temperature raising step of raising a temperature in the second glass-melting furnace from a normal temperature by a burner is performed,

in the temperature increasing step in the second glass-melting furnace, the burner heats the glass melt while preventing contact between the ambient gas in the second glass-melting furnace and the inner peripheral surface of the first outflow path and contact between the ambient gas in the second glass-melting furnace and the inner peripheral surface of a second outflow path made of platinum or a platinum alloy, the second outflow path being used to flow the molten glass out of the second glass-melting furnace, from each other by a shutter.

8. The method for producing a glass article according to any one of claims 1 to 7,

in the continuous forming step, the molten glass stored in the glass melting furnace is heated only by electric heating.