JPWO2007108324A1 - Glass melting method and glass melting furnace - Google Patents

Abstract

The glass melting method of the present invention uses a glass melting furnace equipped with a melting tank, arranges the adjusting tank downstream of the molten glass flow in the melting tank, and adjusts the temperature of the adjusting tank and the amount of gas introduced into the adjusting tank. Thus, the equilibrium state of the moisture concentration at the interface between the atmospheric gas and the molten glass surface is controlled to adjust the moisture concentration in the molten glass.

Description

The present invention relates to a glass melting method and a glass melting furnace for efficiently manufacturing a glass product in the manufacture of a glass product using oxygen combustion.
This application claims the priority based on Japanese Patent Application No. 2006-72235 for which it applied to Japan on March 16, 2006, and uses the content here.

  In recent years, in a glass melting furnace for industrially producing glass, oxyfuel combustion is increasingly used for types of glass that require high-temperature melting (Patent Documents 1 to 3). In particular, in the melting of glass that requires high-temperature melting in a batch-type melting furnace such as a day tank furnace, oxygen combustion is often adopted because air combustion has low thermal efficiency.

  By the way, when oxygen combustion is used for high-temperature melting of glass, since the combustion gas contains a large amount of carbon dioxide and water, there is a concern that the moisture concentration in the glass increases. Water is taken into the glass as OH groups, but depending on the type of glass, such as high-purity silica glass or non-alkali glass, this high OH group content affects the glass structure and adversely affects subsequent processes. There is a possibility that the product yield may be reduced. Note that the water concentration may vary depending on the season, and it is complicated to optimize the water concentration adjustment in a subsequent process of glass melting.

  Patent Document 4 discloses a method for adjusting the moisture concentration in a gas in a glass melting furnace. The purpose of this method is to install a humidifier in the secondary air duct and humidify the air supplied to the melting furnace to maintain a constant humidity, thereby preventing temperature fluctuations in the melting furnace. This method increases the water vapor concentration in air combustion. On the other hand, in oxyfuel combustion, the moisture content in the glass is adjusted by adjusting the moisture concentration in the gas as described above in the method described in Patent Document 4 in order to generate water three times or more that in air combustion. I can't.

When oxygen combustion is employed as a heat source in a glass melting furnace, there is a need for a melting method and a melting furnace that can properly manage the water concentration in the molten glass.
JP-A-6-24752 JP 10-316434 A JP-A-11-11954 JP-A-8-268724

  An object of the present invention is to provide a glass melting method and a glass melting furnace capable of adjusting the moisture concentration in glass even when an oxygen combustion system is used as a glass melting heat source in the glass melting furnace.

  In order to solve the above-mentioned problems, the present invention is a glass melting method using a glass melting furnace provided with a melting tank, wherein the adjusting tank is arranged downstream of the molten glass flow in the melting tank, and the temperature and the adjusting tank are adjusted. By adjusting the amount of gas introduced into the bath, the equilibrium state of the moisture concentration at the interface between the atmospheric gas and the molten glass surface is controlled, and a glass melting method for adjusting the moisture concentration in the molten glass is provided.

  In the present invention, since the effect is particularly great when the raw glass is melted using an oxygen burner, the present invention is preferably applied when the raw glass is melted using an oxygen burner in the melting tank. Moreover, in order to appropriately adjust the water concentration in the molten glass, it is preferable to maintain the pressure in the adjustment tank at a positive pressure.

  Further, the present invention is a glass melting furnace for melting raw glass as a glass melting furnace for carrying out the glass melting method, and adjusts the moisture concentration of the melting tank and the glass melted in the melting tank. An adjustment tank, a throat portion for flowing molten glass from the melting tank to the adjustment tank, and a partition wall for isolating the upper space of the melting tank and the upper space of the adjustment tank, Provided is a glass melting furnace provided with a partition weir provided downstream from the partition wall in the molten glass flow, a molten glass heating means for adjusting the molten glass temperature, and an atmospheric gas inlet.

In the present invention, since the effect is particularly great in a melting furnace equipped with an oxygen burner, the present invention is preferably applied to a melting furnace in which the melting tank is equipped with an oxygen burner.
The molten glass heating means is preferably an immersion electrode and / or an electric heater.
Furthermore, it is preferable that the adjusting tank is provided with an atmospheric gas heating means for adjusting the temperature of the atmospheric gas. The atmospheric gas heating means is preferably an electric heater.

  According to the present invention, in the glass melting furnace, an adjustment tank is provided downstream of the molten glass flow in the melting tank to adjust the moisture concentration in the molten glass. The water concentration in the glass can be properly managed.

It is sectional drawing of the glass fusing furnace for implementing this invention.

Explanation of symbols

  1 .... Glass melting furnace 2 .... Melting tank 3 .... Adjusting tank 4 .... Partition wall 5 ... Throat part 6, ... Division weir 7, ... Adjusting bath 8, ... Oxygen burner, 10 .... Atmosphere gas inlet, 11 .... Electric heater, 12 .... Immersion electrode, 14 .... Glass outlet, 22 ... Raw glass, 23 ... Molten glass

  An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a melting furnace suitable for carrying out the present invention. As shown in the figure, the melting furnace 1 has a melting tank 2 and an adjusting tank 3. The upper space of the melting tank 2 and the adjustment tank 3 is isolated by the partition wall 4.

  The raw material glass 22 in the raw material hopper 20 is put into the melting tank 2 by the raw material feeder 21. The raw glass 22 is melted by a plurality of oxygen burners 8, 8... Installed in the melting tank 2, and sequentially becomes a molten glass 23. The molten glass 23 is introduced into the adjustment tank 3 through the throat portion 5 below the partition wall 4. The adjustment tank 3 is provided with a partition weir 6, and the molten glass 23 overflows the partition weir 6 and is stored in the adjustment bath 7. The raw material is supplied until the amount of accumulated glass in the adjustment bath 7 reaches a predetermined level.

  In the upper space of the adjustment tank 3, an atmospheric gas inlet 10 for adjusting the moisture concentration in the gas phase is provided. By introducing dry nitrogen gas or the like from the atmosphere gas inlet 10 and making the moisture concentration in the atmosphere gas lower than the moisture concentration in the molten glass 23, the moisture content in the glass is reduced at the interface between the atmosphere gas and the surface of the molten glass 23. Diffusion into the atmospheric gas is developed, and the water concentration in the glass is lowered. In the upper space of the melting tank 2 and the adjusting tank 3, a melting tank exhaust gas port 9 and an adjusting tank exhaust gas port 24 through which excess exhaust gas is led out are provided, respectively.

  In the adjustment tank 3, in order to perform heat compensation of the molten glass 23, it is preferable to provide a molten glass heating means. Specifically, heat compensation is performed by installing the electric heater 11 in the upper space of the adjustment tank 3 or by providing the immersion electrode 12 in the molten glass 23 and performing Joule heating. The electrode 12 is preferably made of platinum so as not to be eroded by the molten glass 23, but it is also possible to use molybdenum depending on the glass component. The adjustment tank 3 is preferably provided with an atmospheric gas heating means for adjusting the temperature of the atmospheric gas. Specifically, the electric heater 11 is mentioned.

  It is preferable that the partition weir 6 has a shape in which the side walls are inclined on both the throat portion 5 side and the adjustment bath 7 side, and flows smoothly when the molten glass 23 overflows the partition weir 6. By providing the partition weir 6 having such a shape, the contact area with the atmospheric gas increases when the molten glass 23 flows down the side wall on the adjustment bath 7 side. For this reason, it becomes easier to adjust the water concentration, and the residence time in the adjustment bath 7 can be shortened.

  Moreover, forced stirring of the molten glass also enhances the moisture concentration adjustment effect. Therefore, it is good to provide a stirrer (not shown) in the molten glass 23 or introduce gas bubbling gas from the gas bubbling port 13 to perform gas bubbling. At this time, it is preferable that the moisture concentration of the gas bubbling gas is lower than the moisture concentration in the molten glass 23, similarly to the atmospheric gas. The atmosphere gas and gas bubbling gas introduced into the adjustment tank 3 may be preheated by heat exchange with the combustion exhaust gas discharged from the melting tank 2. The amount of energy used can be reduced by heat exchange.

  The residence time of the molten glass 23 in the adjustment bath 7 varies depending on the type of glass and the amount of melting. Therefore, it is desirable to determine the volume of the adjustment bath 7 so as to ensure an appropriate residence time.

  When the molten glass 23 is adjusted to a desired moisture concentration, the molten glass 23 in the adjustment bath 7 is allowed to flow out from the glass outlet 14 installed at the bottom or lower part of the adjustment bath 7 until the predetermined level is reached, and is then subjected to the next process. send. After the molten glass 23 flows out, the glass outlet 14 is closed again, the raw material glass 22 is charged again into the melting tank 2, and the melting of the glass is started. By repeating this operation, it is possible to manufacture a glass whose moisture concentration is appropriately controlled.

  When the adjustment bath 7 is enlarged and the outflow amount of the molten glass 23 is managed, the continuous production is possible when the residence time for appropriately adjusting the moisture concentration can be secured. When the melting furnace 1 becomes too large, the batch type may be more energy efficient.

(Example 1)

  A melting test of soda-lime glass was performed. A melting furnace 1 having a melting amount of 2 tons / day and a volume of the adjusting bath 7 of 4 tons was used.

  The raw glass 22 began to melt from a state where 50% of the molten glass 23 was stored in the adjustment bath 7, and the molten glass 23 was stored until a predetermined amount was obtained over 24 hours. During this time, adjustment of the atmospheric gas temperature by the electric heater 11 in the upper space and joule heating by the immersion type platinum electrode were performed for heat compensation.

  As the atmospheric gas, dry nitrogen gas preheated by heat exchange with the combustion exhaust gas from the melting tank 2 was used. The preheating temperature was about 300 ° C. A restriction was provided in the exhaust gas port 24 for the adjustment tank so that the inside of the adjustment tank 3 was always kept at a positive pressure to prevent air from entering from the exhaust gas port 9 for the melting tank. After the introduction of the material glass 22 was stopped and the water content was adjusted while introducing nitrogen gas into the adjustment bath 7 for 24 hours, the amount of the molten glass 23 in the adjustment bath 7 was 50% from the glass outlet 14. It was made to flow out until it became, and the glass was molded.

  The steps from the introduction of the raw glass 22 to the outflow of the molten glass 23 are repeated three times, and three plate samples (a) to (c) are cut out from the molded glass obtained in each step, and the moisture concentration is measured. Went. The moisture concentration in the glass was measured by an infrared absorption test, and identified from a comparison with a standard sample using Lambert-Beer's law with an infrared absorption band of OH group (2.8 μm, 3.6 μm).

  The water concentration of the sample obtained in the first step was 400 to 500 ppm. The first step was excluded from the evaluation because it may be affected by the unsteady state until 50% accumulation in the adjustment tank 3. Table 1 shows the moisture measurement results of the second samples 2 (a) to 2 (c) and the samples 3 (a) to 3 (c) obtained in the third step. The moisture concentration of each sample was reduced to around 200 ppm, that is, 220 ppm or less, and it was shown that moisture adjustment at the latter stage of the melting step is unnecessary.

(Comparative Example 1)
Oxygen burners 8, 8,... Were installed in the upper space of the adjustment tank 3 in place of the electric heater 11, and the batch processing of the molten glass 23 was performed under the same conditions as in the examples. Three plate samples (C (a) to C (c)) were cut out from the obtained molded glass, and the water concentration was measured in the same manner as in the examples. The results are shown in Table 1. Samples C (a) to C (c) had a moisture concentration of around 700 ppm.

  In the present invention, even if an oxyfuel combustion system is used as a glass melting heat source, the moisture concentration in the molten glass 23 can be properly managed, so that it is not necessary to adjust moisture at the latter stage of the melting step. Therefore, it is useful industrially.

Claims (8)

A glass melting method using a glass melting furnace provided with a melting tank,
An adjustment tank is placed downstream of the molten glass flow in this melting tank, and the equilibrium state of the moisture concentration at the interface between the atmospheric gas and the molten glass surface is adjusted by adjusting the temperature of the adjusting tank and the amount of gas introduced into the adjusting tank. The glass melting method which has the process of controlling water and adjusting the water concentration in molten glass.   The glass melting method according to claim 1, wherein the raw glass is melted using an oxygen burner in the melting tank.   The glass melting method according to claim 1, wherein the adjustment tank is maintained at a positive pressure. A glass melting furnace for melting raw glass,
A melting tank;
An adjustment tank for adjusting the moisture concentration of the glass melted in the melting tank;
A throat portion for flowing molten glass from the melting tank to the adjustment tank;
A partition wall for isolating the upper space of the melting tank and the upper space of the adjustment tank;
The said adjustment tank is a glass melting furnace provided with the partition weir provided in the downstream of the molten glass flow from the said partition wall, the molten glass heating means for adjusting molten glass temperature, and an atmospheric gas inlet.   The glass melting furnace according to claim 4, wherein the melting tank includes an oxygen burner.   The glass melting furnace according to claim 4, wherein the molten glass heating means is an immersion type electrode and / or an electric heater.   The glass melting furnace according to claim 4, wherein the adjustment tank further includes an atmospheric gas heating means.   The glass melting furnace according to claim 7, wherein the atmospheric gas heating means is an electric heater.

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