WO2014077114A1

WO2014077114A1 - Method for producing alkali-free glass

Info

Publication number: WO2014077114A1
Application number: PCT/JP2013/079170
Authority: WO
Inventors: 良太安藤; 畑　雅之; 裕丈石原
Original assignee: 旭硝子株式会社
Priority date: 2012-11-15
Filing date: 2013-10-28
Publication date: 2014-05-22
Also published as: KR102086435B1; TW201429913A; CN104797537A; JPWO2014077114A1; JP6075383B2; KR20150087203A; CN104797537B

Abstract

The present invention is a method for producing an alkali-free glass, the method including the following: a step for melting a glass raw material and collecting exhaust gas; a step for cooling the exhaust gas by bringing the exhaust gas into contact with a cooling liquid; a step for adding at least one compound selected from among the group consisting of CaCO₃, Ca(OH)₂ and (Ca,Mg)CO₃ to the cooled exhaust gas and recovering from the exhaust gas a powder having an average particle diameter (D50) of 30-100 µm by using a dust collection member; and a step of bringing the exhaust gas from which the powder has been recovered into contact with Mg(OH)₂ and water so as to recover, as a recovered liquid, a component contained in the exhaust gas. The recovered liquid is used as the cooling liquid in the step for cooling the exhaust gas.

Description

Method for producing alkali-free glass

The present invention relates to a method for producing alkali-free glass.

Generally, various components derived from glass raw materials are contained in exhaust gas discharged from a glass melting furnace. For example, when producing borosilicate glass, a boron component containing boron (B) is contained in the exhaust gas. Moreover, the sulfur component containing sulfur (S) is often contained. If these components are released into the atmosphere as they are, there is a risk of adverse effects on the environment, and various methods for removing these components from exhaust gas have been studied.

In addition, non-alkali glass substantially free of alkali metal oxide is used for various display glass substrates and the like.

Patent Document 1 discloses a method for removing boron and sulfur components from exhaust gas by dissolving the boron component and sulfur component in the exhaust gas in water by bringing cooling water and contact water into contact with the exhaust gas. Are listed. The effluent containing the boron component and sulfur component generated by this method can be reused as cooling water or contact water after neutralization.

In the example of Patent Document 1, NaOH is used as a neutralizing agent for drainage, and no precipitate is generated due to neutralization. Therefore, the neutralized drainage is used as it is as a part of cooling water or contact water. Can be reused. Moreover, since the boron component etc. which are contained in exhaust gas are useful as a glass raw material, collect | recovering these and reusing as a glass raw material is also examined.

In Patent Document 2, a fuel that does not substantially contain sulfur is used as a fuel for heating and melting a glass raw material, and an exhaust gas from a glass melting furnace is brought into contact with water to form a collection liquid. A method of recovering arsenic, boron, and chlorine components useful as glass materials by neutralizing the liquid to obtain a neutralized collection liquid, followed by solid-liquid separation of the neutralized collection liquid and drying by heating. Are listed.

International Publication No. 2009/072612 Japanese Unexamined Patent Publication No. 2004-238236

In the method described in Patent Document 1, when NaOH is used as a neutralizing agent for drainage, sodium salt that is an alkali metal salt is contained in the drained liquid after neutralization. The neutralized effluent contains boron and sulfur components that can be reused as glass raw materials, but also contains alkali metal salts. Use this effluent for the production of alkali-free glass. Is not suitable.

In the method described in Patent Document 2, a spray dryer is used as a solid-liquid separation means, and the useful components recovered are mainly a relatively large solid content of several hundred μm or more. If the solid content is relatively large, it may be difficult to mix homogeneously with other components when reused as a glass raw material.

Further, in the method described in Patent Document 2, the amount of calcium compound added as a neutralizing agent is large in the useful component recovery cycle, and therefore, in order to reuse as a glass raw material, There is a problem that the calcium component becomes excessive.

One object of the present invention is to recover a reusable component in powder form from exhaust gas discharged from a glass melting furnace and to provide a method for producing alkali-free glass whose composition is suitable as a glass raw material And

As one aspect of the present invention, SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0.1 to 12%, MgO: 0.5-10%, CaO: 0.5-14.5%, SrO: 0-24%, BaO: 0-13.5%, ZrO ₂ : 0-5%, Cl: 0.01-0. 35%, F: 0.01-0.15%, and SO ₃ : 0.0001-0.0025%, MgO + CaO + SrO + BaO: 8-29.5%, MgO / (MgO + CaO): 0.1-0. 8 is a method for producing an alkali-free glass, a step of melting a glass raw material to collect exhaust gas, a step of bringing a cooling liquid into contact with the exhaust gas to cool the exhaust gas, and CaCO ₃ to the cooled exhaust gas. , Ca _{(OH) 2} and (Ca, Mg) CO ₃ or One or more selected from the group consisting of the above, a step of recovering powder having an average particle size (D50) of 30 to 100 μm from the exhaust gas using a dust collecting member, and Mg in the exhaust gas from which the powder is recovered (OH) ₂ and water are brought into contact with each other and a component contained in the exhaust gas is recovered as a recovered liquid, and the recovered liquid is used as the cooling liquid in the step of cooling the exhaust gas. It is.

According to the present invention, a reusable component is recovered in powder form from exhaust gas discharged from a glass melting furnace, and a method for producing alkali-free glass whose composition is suitable as a glass raw material is provided. it can.

FIG. 1 shows a flow chart of an example of a method for producing glass according to an embodiment of the present invention. FIG. 2 shows a schematic diagram of a production line as an example of a glass production method according to an embodiment of the present invention. FIG. 3 shows an example flow diagram for manufacturing a glass product according to one embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail.

FIG. 1 shows a flow chart of an example of a method for producing an alkali-free glass (hereinafter sometimes simply referred to as “glass”) of the present embodiment.

In FIG. 1, the glass raw material is melted at 1001 to collect the exhaust gas, and the exhaust gas is cooled by bringing the cooling liquid into contact with the exhaust gas at 1002, and the COCO ₃ , Ca (OH) ₂ and ( One or more selected from the group consisting of (Ca, Mg) CO ₃ (hereinafter sometimes simply referred to as “Ca compound”) is added, and the recovered powder is recovered from the exhaust gas using a dust collecting member, In 1004, Mg (OH) ₂ and water are brought into contact with the exhaust gas after the powder is recovered, and the components contained in the exhaust gas are recovered as a recovery liquid. Hereinafter, 1004 is also referred to as a Mg (OH) ₂ treatment step. At 1005, exhaust gas can be exhausted after the recovered liquid is recovered at 1004.

The recovered liquid recovered in 1004 is used as a cooling liquid in the process of cooling the exhaust gas in 1002. Further, the recovered powder recovered in 1003 may be used as a glass raw material in 1001 and circulated in the system. Further, the recovered powder may be taken out for use in another system without being circulated in the system.

According to the present embodiment, a reusable component is recovered in powder form from the exhaust gas discharged by melting the glass, and a glass manufacturing method whose composition is suitable as a glass raw material can be provided. As a result, it is possible to remove a component that may cause a load on the environment from the exhaust gas and release it into the atmosphere, and it is possible to reuse the boron component or the like in the exhaust gas as a glass raw material.

According to this embodiment, the Mg component added in the 1004 Mg (OH) ₂ treatment step circulates in the system, and can be recovered as a powder together with the Ca component added in the powder recovery step. Thereby, since the composition of the recovered powder includes not only the Ca component but also the Mg component, a composition that can be easily reused as a glass raw material can be provided.

Further, since the recovered powder recovered in 1003 is in the form of a powder having an average particle diameter (D50) of 30 to 100 μm, the range of usage when reusing as a glass raw material can be expanded. That is, it can be used as it is as a powder, a separate component can be added to the powder, and a granulated body can be produced and used. Moreover, when the particle diameter of the powder is small, it can be more uniformly mixed with other components when reused as a glass raw material.

Furthermore, at 1004, the recovered liquid can be recovered in the form of a solution by recovering the recovered liquid with Mg (OH) ₂ and water. The slurry liquid may damage the pipes and nozzles when passing through the pipes in the system and the nozzles used when spraying the liquid in each process, so the recovered liquid may be in the form of a solution. desirable.

Magnesium hydroxide is used as a neutralizing agent for general acid drainage because it is cheap and easy to handle, but its solubility in water is low and it is usually in a slurry state. When doing so, there is a concern of clogging of piping. On the other hand, the inventors of the present invention have obtained the knowledge that when magnesium hydroxide slurry is added to a liquid containing a boron component, an aqueous solution is obtained despite containing magnesium.

Further, in the powder recovery step 1003, by adding the Ca component, the component derived from the fining agent can be recovered as a powder, and can be reused as a glass raw material. In particular, the fluorine (F) component derived from the fining agent can be removed in the powder recovery step. As a result, it is possible to prevent the fluorine component from being mixed into the subsequent Mg (OH) ₂ treatment step, and in the Mg (OH) ₂ treatment step, the fluorine component reacts with Mg (OH) ₂ to form a slurry. Can be prevented.

Further, the powder recovered by the powder recovery process 1003 is in a dry state and does not require heat treatment, and can be used as it is as a glass raw material.

<Glass composition>
The glass produced according to the present embodiment has a mass percentage based on oxides of SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0.1 to 12%, Preferably 0.3 to 12%, more preferably 0.5 to 12%, MgO: 0.5 to 10%, CaO: 0.5 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, ZrO ₂ : 0 to 5%, Cl: 0.01 to 0.35%, F: 0.01 to 0.15%, and SO ₃ : 0.0001 to 0.0025%, MgO + CaO + SrO + BaO: 8 to 29.5%, MgO / (MgO + CaO): 0.1 to 0.8. This glass composition is a composition of solid glass obtained by melting and solidifying a glass raw material.

Glass having such a glass composition can be used as non-alkali glass (hereinafter also referred to as non-alkali borosilicate glass).
In the glass produced according to this embodiment, the total content of alkali metal oxides is preferably 1% or less, more preferably 0.1% or less, and the alkali metal oxide is substantially reduced. It is preferably not included.

Here, the alkaline earth metal mainly means calcium (Ca), strontium (Sr), and barium (Ba).
Alkali metal mainly means lithium (Li), sodium (Na), and potassium (K).
The “boron component” is a general term for components containing a boron atom (B) (the same applies to other components).

[SiO ₂ ]
SiO ₂ is a glass network former and is an essential component. SiO ₂ is highly effective in increasing the acid resistance of the glass and reducing the density of the glass. The content is generally 73% or less, preferably 66% or less, considering that the viscosity of the molten glass becomes too high and it becomes difficult to produce the molten glass by a normal melting method. More preferably, it is 61.5% or less. On the other hand, if the amount of SiO ₂ is too small, it may cause deterioration of acid resistance, increase in linear expansion coefficient, etc., so in the case of display substrate glass, its content is preferably 50% or more, more preferably 54%. Or more, more preferably 58% or more.

[Al ₂ O ₃ ]
Al ₂ O ₃ is a component used for the purpose of increasing the strain point of the glass and suppressing the phase separation of the glass. The content of Al ₂ O ₃ is preferably 10.5% or more, more preferably 15% or more. On the other hand, the content of Al ₂ O ₃ is preferably 24% or less, more preferably 22.5% or less from the viewpoint of avoiding high viscosity of molten glass, devitrification characteristics of glass, and deterioration of acid resistance. More preferably, it is 22% or less, and more preferably 15% or less.

[B ₂ O ₃ ]
B ₂ O ₃ is a glass network former, and is also a component that improves the dissolution reactivity in melt vitrification. The content of B ₂ O ₃ is 0.1 to 12%, preferably 0.3 to 12%, more preferably 0.5% or more, still more preferably 5% or more, and particularly preferably 7%. % Or more. On the other hand, B ₂ O ₃ may reduce the acid resistance of the glass and is usually 12% or less. In the case of a substrate glass for display, the content of B ₂ O ₃ is preferably 10% or less, more preferably. 8% or less.

[MgO]
MgO is a component that lowers the viscosity of molten glass, lowers the density of glass, does not increase the linear expansion coefficient, and improves melting reactivity. It is an essential component when manufacturing a substrate. In the present embodiment, the content of MgO is 0.5% or more, preferably 1% or more, more preferably 2% or more, and still more preferably 4% or more. On the other hand, in order to avoid phase separation of the glass, the content is 10% or less, more preferably 8% or less, and further preferably 5% or less from the viewpoint of increasing acid resistance.

[CaO]
CaO is a component that lowers the viscosity of molten glass, and is a component that may be used for the purpose of adjusting glass properties such as density, linear expansion coefficient, and strain point. The content of CaO is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, and still more preferably 4% or more. On the other hand, the content is preferably 14.5% or less, more preferably 10% or less, and still more preferably 9% or less, from the viewpoint of avoiding deterioration of the devitrification characteristics of the glass, increase of the linear expansion coefficient, and the like. It is.

[SrO]
SrO is a component that lowers the viscosity of the molten glass, and is a component that may be included to improve the devitrification properties and acid resistance of the glass. In the case of containing SrO, the content is preferably 1% or more, more preferably 2% or more, and still more preferably 3% or more. The content is preferably 24% or less, more preferably 16% or less, still more preferably 12.5% or less, and even more preferably 6% or less.

[BaO]
BaO is a component that lowers the viscosity of the molten glass, and is a component that can be added for the purpose of, for example, phase separation of glass, improvement of devitrification characteristics, and improvement of acid resistance. However, when the glass is a glass substrate for liquid crystal in order to increase the density or the like, it is preferable to make the content inevitable. In addition, the content when BaO is positively contained is preferably 13.5% or less, more preferably 10% or less, still more preferably 5% or less, and still more preferably 2% or less.

[ZrO ₂ ]
ZrO ₂ is not essential, but may be contained at 5% or less in order to lower the glass melting temperature or to promote crystal precipitation during firing. By being 5% or less, the glass can be stabilized and ε can be reduced. Preferably it is 3% or less.

[Cl]
Cl is a component added for defoaming as a fining agent, and is contained at 0.01% to 0.35%. From the viewpoint of defoaming and re-boiling suppression, it is more preferably 0.30% or less, and still more preferably 0.25% or less. In order to further promote defoaming, it is more preferably 0.05% or more, further preferably 0.1% or more.

[F]
F, like Cl, is a component added for defoaming as a fining agent, and is contained at 0.01 to 0.15%. F has an effect of reducing the surface tension of the molten glass and easily breaking bubbles existing on the surface of the molten glass, or an effect of reducing minute bubbles in the molten glass. From the viewpoint of defoaming and re-boiling suppression, it is more preferably 0.10% or less, and still more preferably 0.05% or less. In order to further promote defoaming, the content is more preferably 0.02% or more, further preferably 0.03% or more.

[SO ₃ ]
SO ₃ is added as a fining agent and is a component that promotes defoaming or melting of the glass raw material, and is contained at 0.0001 to 0.0025%. From the viewpoint of suppressing re-boiling, it is more preferably 0.0010% or less. When it is desired to further promote defoaming or melting of the glass raw material, it is more preferable to contain 0.0012% or more of SO ₃ . The SO ₃ content is usually carried out by adding a sulfate such as bow glass to the glass raw material. In addition, for example, in heavy oil combustion kilns, it is also caused by S-containing impurities in heavy oil.

[MgO + CaO + SrO + BaO]
If the total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is small, the viscosity of the molten glass increases and the melting reactivity deteriorates. The total content of these is preferably 8% or more, more preferably 9% or more, and further preferably 16% or more. On the other hand, from the viewpoint of avoiding an increase in glass density and an increase in linear expansion coefficient, the total content thereof is preferably 29.5% or less, more preferably 26% or less, still more preferably 18% or less, even more. Preferably it is 15% or less.

[MgO / (MgO + CaO)]
MgO / (MgO + CaO) obtained by dividing the content of MgO by the total content of MgO and CaO is preferably 0.1 to 0.8 in terms of the mass ratio based on the oxide. By being 0.2 or more, an increase in specific gravity and an increase in expansion coefficient can be prevented. From the viewpoint of strain point and solubility, it is more preferably 0.25 to 0.55, still more preferably 0.3 to 0.5, and still more preferably 0.3 to 0.4.

[Other glass components]
Other examples of the glass component that can be contained are not particularly limited, and may include a solubilizer, a molding agent, and the like. As a clarifier, components other than the above-described Cl, F, and SO ₃ may be included. _{_{_{_{Further, Fe 2 O 3, TiO 2}}}} , Y 2 O 3 or the like may be appropriately contained.

[Example of glass composition]
From the viewpoint of increasing the strain point and the solubility, more preferable examples of the glass composition include SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O in terms of mass percentage based on oxide. ₃ : 5 to 12%, MgO: 0.5 to 8%, CaO: 0.5 to 9%, SrO: 3 to 12.5%, BaO: 0 to 2%, Cl: 0.01 to 0.35 %, F: 0.01 to 0.15%, and SO ₃ : 0.0001 to 0.0025%, MgO + CaO + SrO + BaO: 9 to 18%, MgO / (MgO + CaO): 0.35 to 0.55 .

Particularly preferable examples of the glass composition from the viewpoint of increasing the solubility include SiO ₂ : 50 to 61.5%, Al ₂ O ₃ : 10.5 to 18%, and B ₂ O ₃ : 7 to 10%, MgO: 2 to 5%, CaO: 0.5 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, Cl: 0.01 to 0 .35%, F: 0.01 to 0.15%, and SO ₃ : 0.0001 to 0.0025%, MgO + CaO + SrO + BaO: 16 to 29.5%, MgO / (MgO + CaO): 0.3 to 0 .5.

In particular, from the viewpoint of increasing the strain point, more preferable examples of the glass composition include SiO ₂ : 54 to 73%, Al ₂ O ₃ : 10.5 to 22.5%, B 2 ₂ O ₃ : 0.1 to 12%, preferably 0.3 to 12%, more preferably 0.5 to 5.5%, MgO: 0.5 to 10%, CaO: 0.5 to 9%, SrO: 0 to 16%, BaO: 0 to 2.5%, Cl: 0.01 to 0.35%, F: 0.01 to 0.15%, and SO ₃ : 0.0001 to 0.0025% MgO + CaO + SrO + BaO: 8 to 26%, MgO / (MgO + CaO): 0.3 to 0.8.

<Glass raw material>
In the present embodiment, the glass raw material is a compound that can be an oxide as a glass component, and may be in the form of a powder or a granulated body. The glass raw material may contain the following silicon source, aluminum source, boron source and the like. Known raw material powders can be appropriately selected and used.

The composition of the glass raw material can be designed so as to obtain the desired glass composition.
The composition of the glass raw material is substantially the same as the glass composition to be obtained on the oxide basis, except for boron oxide. Boron oxide is preferably blended so that the amount of boron source in the glass raw material is increased on an oxide basis, usually by an amount considering the volatile content, compared to the boron oxide content in the glass composition to be obtained.

Further, the glass raw material can contain a clarifying agent, a colorant, a melting aid, an opacifier, etc. as auxiliary raw materials as required. As these auxiliary materials, known components can be appropriately used.
Among these, the fining agent component is volatilized and collected as exhaust gas in the glass melting step, and can be recovered as a recovered powder. In that case, the recovered powder can be used as a fining agent raw material.

[Silicon source]
The raw material powder as a silicon source is a powder of a compound that can be a SiO ₂ component during the glass production process. Silica sand is preferably used as the silicon source.

[Aluminum source]
The raw material powder as the aluminum source is a powder of a compound that can be an Al ₂ O ₃ component during the glass production process. Aluminum oxide, aluminum hydroxide and the like are preferably used. These may be used alone or in combination of two or more.

[Boron source]
The raw material powder as a boron source is a powder of a compound that can be a B ₂ O ₃ component during the glass production process. Specific examples include boric acid such as orthoboric acid (H ₃ BO ₃ ), metaboric acid (HBO ₂ ), tetraboric acid (H ₂ B ₄ O ₇ ), boron oxide (B ₂ O ₃ ), and colemanite. It is done. These may be used alone or in combination of two or more. Orthoboric acid is preferred because it is inexpensive and easily available. Colemanite is also a calcium source described later.

[Magnesium source]
The raw material powder as the magnesium source is a powder of a compound that can be an MgO component during the glass production process. Specific examples include magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂ ), magnesium carbonate (MgCO ₃ ), and the like.

[Alkaline earth metal source]
The raw material powder as the alkaline earth metal source is a powder of a compound that can be SrO, CaO, or BaO during the glass production process. As specific examples, carbonates such as calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ), dolomite (ideal chemical composition: CaMg (CO ₃ ) ₂ ); calcium oxide (CaO), Oxides such as barium oxide (BaO) and strontium oxide (SrO); calcium hydroxide (Ca (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ), strontium hydroxide (Sr (OH) ₂ ) and the like Hydroxides. These may be used alone or in combination of two or more. Dolomite is also the aforementioned magnesium source.

[Zirconia source]
The raw material powder as a zirconia source is a powder of a compound that can be a ZrO ₂ component during the glass production process. Examples of the zirconia source include zirconium dioxide and zircon.

[Clarifier]
The glass raw material can contain sulfate, chloride, or fluoride, for example, as a fining agent. These may use 1 type and may use 2 or more types.

As the sulfate, chloride, or fluoride, a compound containing an oxide cation constituting glass can be used. Specifically, Mg or alkaline earth metal sulfate, chloride, or fluoride can be used. When these are used, Mg sulfate, chloride, or fluoride is the source of magnesium. The alkaline earth metal sulfate, chloride, or fluoride is the source of the alkaline earth metal.

<Glass manufacturing method>
Hereinafter, with reference to FIG. 2, an example of the manufacturing method of the glass of this embodiment is demonstrated in more detail. FIG. 2 is a diagram schematically showing a production line which is an example of the glass production method of the present embodiment.

The production line shown in FIG. 2 includes a glass melting furnace 1, a first cooling tower 2, a bag filter 3 as a dust collecting member, a second cooling tower 4, a scrubber (exhaust gas cleaning device) 6, a centrifugal dust collector 8, a chimney 10, A recovery liquid tank 14, a Mg (OH) ₂ addition device 16, a circulation pump 17, a Ca compound supply device 18, and a recovery powder tank 19 are provided.

"1. Melting glass raw materials and collecting exhaust gas"
The present embodiment includes a step of melting a glass raw material and collecting exhaust gas. The glass raw material may be in the form of a powder or a granulated body.

In the glass manufacturing method of the present embodiment, a glass raw material is charged into the glass melting furnace 1 and melted to obtain molten glass. Examples of the glass melting method include a normal melting method using an Siemens type glass melting furnace, an air melting method, and the like. In this embodiment, the ordinary melting method is preferable.

[Normal melting method]
In the ordinary melting method, a glass raw material is put on the surface of a molten glass already melted in a glass melting furnace, and this glass raw material (also called a batch pile or batch pile) is heated by a burner or the like. This is a method in which melting is advanced to gradually form molten glass.

[Air melting method]
In the air melting method, at least a part of glass particles (including a granulated body) contained in a glass raw material is melted into a molten glass particle in a gas phase atmosphere, and the molten glass particles are accumulated to form a molten glass. Is the method. Specifically, first, a glass raw material is introduced into a high-temperature gas phase atmosphere of an air heating device. A well-known thing can be used for an air heating apparatus.

[Collecting exhaust gas]
The exhaust gas generated in the melting process of the glass raw material in the present embodiment is the exhaust gas G0 generated from the glass melting furnace 1 in FIG. The exhaust gas G0 includes gas components derived from the constituent components of the glass raw material charged into the glass melting furnace 1.

As the gas component, a boron component can be mainly cited. The boron component in the exhaust gas G0 is, for example, boric acid or boron oxide.

The exhaust gas G0 includes components derived from fining agents, such as components containing sulfur atoms (S) (also referred to as sulfur components), components containing chlorine atoms (Cl) (also referred to as chlorine components), fluorine atoms (F). May contain a component (also referred to as a fluorine component) or the like. Further, when a fuel containing sulfur such as heavy oil is burned in the glass melting furnace 1, the exhaust gas G0 contains a sulfur component derived from this fuel.

Sulfur components in the exhaust gas G0 are mainly oxides (SO _x ).
The chlorine component in the exhaust gas G0 is mainly HCl.
The fluorine component in the exhaust gas G0 is mainly HF.

When the exhaust gas G0 discharged from the glass melting furnace 1 contains a sulfur component and a chlorine component, when these components are dissolved in water and reacted with Mg (OH) ₂ , magnesium salts (MgSO ₄ , MgCl ₂₎ ) Is generated.

Therefore, the method of the present embodiment is also suitable when the exhaust gas G0 contains a sulfur component and / or a chlorine component in addition to the boron component, and these components are recovered as a magnesium salt in the Mg (OH) ₂ treatment step. Thus, it can be reused for the production of glass. This allows the recovered MgSO ₄ and / or MgCl _{2 to} be reused as a magnesium source and as sulfate and / or chloride as a fining agent.

In addition, when the fluorine component is contained in the exhaust gas G0, the fluorine component is adsorbed to the Ca compound in the bag filter 3 in front of the second cooling tower 4 and the scrubber 6 that performs the Mg (OH) ₂ treatment, and is used as a recovered powder. It can be recovered. Therefore, a fluorine component is magnesium salt (MgF _2), it is possible to prevent contained as solids in the recovery liquid.

“2. Exhaust gas cooling process”
Next, the present embodiment includes a step of cooling the exhaust gas by bringing the cooling liquid into contact with the exhaust gas. In FIG. 2, the exhaust gas G0 collected from the glass melting furnace 1 is supplied to the first cooling tower 2 through a pipe, and the cooling liquid is brought into contact with the exhaust gas G0 in the first cooling tower 2 to cool the exhaust gas G0.

By cooling the exhaust gas G0 in the first cooling tower 2, the temperature of the exhaust gas G1 supplied to the subsequent bag filter 3 can be lowered, and the bag filter 3 can be prevented from being damaged by heat. For example, damage to the furnace cloth portion of the bag filter 3 can be prevented, and the life of the furnace cloth can be extended.

The temperature of the exhaust gas G0 immediately before being supplied to the first cooling tower 2 is not particularly limited. The temperature of the exhaust gas G0 is usually 1000 to 1600 ° C. in a state where the exhaust gas is collected from the glass melting furnace 1, and may be supplied to the first cooling tower 2 at that temperature. Further, it may be 350 to 1000 ° C. by being cooled to some extent by piping or the like.

In the first cooling tower 2, the cooling liquid is brought into contact with the exhaust gas G0. For example, a nozzle can be provided in the upper part in the 1st cooling tower 2, and the liquid for cooling can be sprayed to exhaust gas G0 from a nozzle. When the exhaust gas G0 comes into contact with the cooling liquid, the temperature decreases, and the exhaust gas G0 is discharged as the exhaust gas G1 after cooling. At this time, a part of the components in the exhaust gas G0 may be dissolved in the cooling liquid. The cooling liquid in contact with the exhaust gas G0 is dispersed in the exhaust gas G0 and supplied to the subsequent bag filter 3 as the exhaust gas G1. When a part of the cooling liquid is stored at the bottom of the first cooling tower 2, it may be sprayed again on the exhaust gas G0.

In the present embodiment, the recovered liquid recovered in the Mg (OH) ₂ processing step described later is used as the cooling liquid. This recovered liquid is preferably an aqueous liquid mainly containing water and Mg salt. Since the recovered liquid has a small solid content, it is possible to prevent damage to the piping and the apparatus due to the solid content. In particular, damage to the nozzles of the first cooling tower 2 can be prevented.

The cooling liquid is not particularly limited in the initial stage of the production line, and a liquid that can cool the exhaust gas G0 by contacting with the exhaust gas G0 can be used. In this case, those that dissolve the components in the exhaust gas G0 are preferred, and water (industrial water, distilled water, etc.) or aqueous solutions (the solute is acceptable as a component in the glass raw material) are preferred. In addition to the recovered liquid, these cooling liquids may be used in combination.

The temperature of the exhaust gas G1 after cooling is preferably 350 ° C. or lower, and more preferably 250 ° C. or lower. This can prevent the material of the subsequent device from being damaged by heating. The lower limit of the temperature of the exhaust gas G1 after cooling is preferably in a temperature range in which components in the gas do not precipitate. For example, 150 degreeC or more is preferable and 180 degreeC or more is more preferable.

“3. Powder recovery process”
Next, in the present embodiment, the cooled exhaust gas is selected from the group consisting of CaCO ₃ , Ca (OH) ₂ (also referred to as slaked lime) and (Ca, Mg) CO ₃ (also referred to as dolomite). A step of adding the above Ca compound and collecting powder having an average particle size (D50) of 30 to 100 μm from the exhaust gas using the bag filter 3 as a dust collecting member.

In FIG. 2, the exhaust gas G1 from the first cooling tower 2 is supplied to the bag filter 3 through a pipe, and the Ca compound is added from the Ca compound supply unit 18 between them, and the recovered powder is recovered from the exhaust gas G1 by the bag filter 3. to recover. Reference symbol G <b> 2 in the figure indicates exhaust gas before being exhausted from the bag filter 3 and supplied to the second cooling tower 4.

The recovered powder is supplied to the recovered powder tank 19. Thereafter, as described later, it is supplied to the glass melting furnace 1 and can be reused as a glass raw material. Note that the recovered powder tank 19 may be directly supplied to the glass melting furnace 1 by piping without providing the recovered powder tank 19.

In the Ca compound supply device 18, CaCO ₃ , Ca (OH) ₂ and (Ca, Mg) CO ₃ can be supplied alone or in combination. These are preferably supplied in an amount of 1.0 to 5.0 g, more preferably 2.0 to 3.0 g, with respect to 1 Nm ^{3 of} the exhaust gas G1.

Here, considering the removal rate of boron components, sulfur components, chlorine components, fluorine components, etc. in the exhaust gas G1 supplied to the bag filter 3 (that is, reactivity at the bag filter), the Ca compound is Ca (OH ) ₂ and / or CaCO ₃ are preferred, and Ca (OH) ₂ is more preferred.

In consideration of reducing the increase in β-OH in the glass when the recovered raw material is reused as a glass raw material, CaCO ₃ and / or (Ca, Mg) CO ₃ is preferable, and (Ca, Mg) CO ₃ is more preferred. β-OH is water contained in the molten glass, and if it is contained in the glass, the combustion efficiency may be lowered.

On the other hand, considering stable production of glass (that is, improvement of removal rate of boron component, sulfur component, chlorine component, fluorine component, etc. in bag filter 3 and reduction of β-OH in glass), Ca (OH) ₂ And / or (Ca, Mg) CO ₃ is preferred, and Ca (OH) ₂ is more preferred.

A well-known bag filter 3 can be used as appropriate. By providing the bag filter 3, the solid content in the exhaust gas G1 can be removed.

When the fluorine component is contained in the exhaust gas G1, the above-described Ca compound is supplied into the exhaust gas G1 in the path from the first cooling tower 2 to the bag filter 3, thereby removing the fluorine component in the exhaust gas G1. Can do. The Ca compound may be added in powder form. The Ca compound is removed by the bag filter 3 together with the fluorine component after adsorbing the fluorine component in the exhaust gas G1. By removing the fluorine component in the exhaust gas G1 in advance in this way, magnesium that is hardly soluble in water due to the reaction between the fluorine component and Mg (OH) _{2 in} the Mg (OH) ₂ treatment step described later. Formation of a salt (MgF ₂ ) can be prevented.

In the bag filter 3, the concentration of the fluorine component contained in the exhaust gas G2 after powder recovery is preferably 30 mg / Nm ³ or less, more preferably 10 mg / Nm ³ or less, and even more preferably 5 mg / Nm ^3. It is as follows. As a result, it is possible to prevent the fluorine component from being mixed in the subsequent Mg (OH) ₂ treatment process and to prevent the formation of a magnesium salt (MgF ₂ ) that is hardly soluble in water. Further, the recovered powder recovered by the bag filter 3 contains a fluorine component, and when this is reused as a glass raw material, a composition containing the fluorine component as a refining agent can be provided.

The concentration of the fluorine component can be obtained from the amount of fluorine component per 1 Nm ^{3 of} the exhaust gas by collecting the exhaust gas with a metering pump and absorbing it into the absorption liquid, measuring the concentration of the fluorine component in the solution with ICP.

“4. Mg (OH) ₂ treatment process”
Next, this embodiment includes a step of bringing Mg (OH) ₂ and water into contact with the exhaust gas from which the powder has been recovered to recover the components contained in the exhaust gas as a recovery liquid.

In FIG. 2, after the powder is collected from the exhaust gas G1 by the bag filter 3, the exhaust gas G2 is supplied to the second cooling tower 4, and the first contact liquid L1 is brought into contact with the exhaust gas G2 in the second cooling tower 4. Then, the exhaust gas G3 is supplied to the scrubber 6, and the second contact liquid L2 is then brought into contact with the exhaust gas G3 in the scrubber 6. The first contact liquid L1 and the second contact liquid L2 contain Mg (OH) ₂ and water, and after being processed by the second cooling tower 4 and the scrubber 6, the first recovery liquid S1 and the second recovery liquid S1 The recovered liquid S2 is recovered in the recovered liquid tank 14.

The first contact liquid L1 and the second contact liquid L2 contain Mg (OH) ₂ as a neutralizing agent. In the present embodiment, after being used in the second cooling tower 4 and the scrubber 6, the first recovered liquid S1 and the second recovered liquid S2 circulate in the system.

Here, if the neutralizing agent contains a Ca component, a precipitate such as gypsum and calcium borate is generated in the recovery liquid tank 14. Such a deposit adheres to the bottom of the recovery liquid tank 14, the bottom of the first cooling tower 2, the bottom of the second cooling tower 4, the bottom of the scrubber 6, and the pipes connecting them, the nozzles of each device, and the like. And may be closed. Therefore, it is desirable that no Ca component is contained as a neutralizing agent.

Further, the glass composition according to the present embodiment includes a predetermined amount of MgO. When calcium hydroxide is used as a neutralizing agent, since the Mg component is not included, the Mg component in the recovered powder is insufficient, which is not preferable.

The temperature of the exhaust gas G2 immediately before being supplied to the second cooling tower 4 is not particularly limited. For example, 130 to 180 ° C. is preferable.

In the second cooling tower 4, the first contact liquid L1 is brought into contact with the exhaust gas G2. In the example shown in FIG. 2, the second cooling tower 4 includes an introduction pipe part 4a into which the exhaust gas G2 is introduced from the upper part, and a cooling tower in which the exhaust gas G2 supplied from the introduction pipe part 4a is introduced from the lower part and discharged to the upper part. Part 4b. The first contact liquid L1 is sprayed in the flow direction of the exhaust gas G2 from the nozzle provided in the upper portion of the introduction portion 4a, and is in the direction opposite to the flow of the exhaust gas G2 from the nozzle provided in the lower portion of the cooling tower portion 4b. Sprayed on.

The temperature of the exhaust gas G2 is lowered by contacting with the first contact liquid L1, and is discharged as exhaust gas G3 after cooling. At this time, a part of the components in the exhaust gas G2 may be dissolved in the first contact liquid L1. The first contact liquid L1 that has come into contact with the exhaust gas G2 is stored as a first recovered liquid S1 at the bottom of the second cooling tower 4.

The first contact liquid L1 is preferably a liquid containing water and Mg (OH) ₂ . When the second contact liquid L2 described later is a liquid containing water and Mg (OH) ₂ , the first contact liquid L1 is not limited to a liquid containing water and Mg (OH) ₂ , and the exhaust gas G2 What is necessary is just to be able to cool the exhaust gas G2 by contacting with. In this case, what dissolves the components in the exhaust gas G2 is preferable, and water (industrial water, distilled water, etc.) or an aqueous solution (solute is acceptable as a component in the glass raw material) is preferable. In the present embodiment, the first contact liquid L1 at the start of operation is water, and a part of the recovered liquid recovered in the recovery liquid tank 14 described later can be reused as the first contact liquid L1. it can.

The temperature of the exhaust gas G3 after cooling is preferably 80 ° C. or lower, and more preferably 70 ° C. or lower. This can prevent subsequent devices from being damaged by heat. The lower limit of the temperature of the exhaust gas G3 after cooling is preferably within a temperature range in which components in the gas are not precipitated. For example, 40 degreeC or more is preferable and 60 degreeC or more is more preferable.

After cooling, the exhaust gas G3 is supplied to the scrubber 6 through the pipe 5. As the scrubber 6, a known scrubber (exhaust gas cleaning device) can be used. For example, a venturi scrubber can be used.

In the scrubber 6, the second contact liquid L2 is brought into contact with the exhaust gas G3 after cooling. For example, a nozzle can be provided in the upper part of the scrubber 6 to spray the second contact liquid L2. By bringing the second contact liquid L2 into contact with the exhaust gas G3 after cooling, the boron component in the exhaust gas G3 after cooling is dissolved in the second contact liquid L2. At this time, components other than the boron component in the exhaust gas G3 after cooling may be dissolved in the second contact liquid L2.

For example, when the exhaust gas G0 contains a sulfur component and / or a chlorine component, the sulfur component and / or chlorine component in the exhaust gas G3 after cooling is dissolved in the second contact liquid L2.

The second contact liquid L2 is preferably a liquid containing water and Mg (OH) ₂ . When the first contact liquid L1 described above is a liquid containing water and Mg (OH) ₂ , the second contact liquid L2 is not limited to a liquid containing water and Mg (OH) ₂ , and the exhaust gas G3. Is used, which can dissolve at least the boron component in the exhaust gas G3 and remove it from the gas. In this case, water (industrial water, distilled water, etc.) or an aqueous solution (a solute is acceptable as a component in the glass raw material) is preferable. In the present embodiment, the second contact liquid L2 at the start of operation is water, and the recovered liquid recovered in the recovery liquid tank 14 described later can be reused as the second contact liquid L2.

In order to efficiently clean the exhaust gas, the second contact liquid L2 of the first contact liquid L1 and the second contact liquid L2 is more preferably a liquid containing water and Mg (OH) _2. Preferably, both are liquids containing water and Mg (OH) ₂ .

In the present embodiment, the high differential pressure portion 7 may be provided in the scrubber 6. For example, immediately after the second contact liquid L2 is sprayed on the exhaust gas G3 after cooling, these mixed fluids pass through the high differential pressure portion 7 that causes a pressure loss. As a result, the mixed fluid becomes a turbulent state, and the exhaust gas G3 after cooling and the second contact liquid L2 are more sufficiently mixed, and the components in the exhaust gas G3 after cooling into the second contact liquid L2. Can be further promoted.

The second contact liquid L2 after coming into contact with the exhaust gas G3 after cooling is stored at the bottom of the scrubber 6 as the second recovered liquid S2.

In this way, it is possible to obtain the clean gas G4 from which the boron component in the exhaust gas G3 after cooling is dissolved and removed in the recovered liquid.

In this embodiment, a centrifugal dust collector 8 may be provided. For example, the clean gas G4 is discharged from the chimney 10 to the atmosphere after the mist-like water is removed by the centrifugal dust collector 8 to become the exhaust clean gas G5. In the present embodiment, a fan 9 may be provided between the centrifugal dust collector 8 and the chimney 10, whereby the gas flow rate in the apparatus from the entrance of the second cooling tower 4 to the exit of the chimney 10 can be adjusted.

The mist-like water separated by the centrifugal dust collector 8 is stored as a third recovered liquid S3 at the bottom of the centrifugal dust collector 8.

The first recovered liquid S <b> 1 is extracted from the bottom of the second cooling tower 4 through the pipe 11 and collected in the recovered liquid tank 14.
The second recovered liquid S2 is extracted from the bottom of the scrubber 6 through the pipe 12 and collected in the recovered liquid tank 14.
The third recovered liquid S3 is extracted from the bottom of the centrifugal dust collector 8 through the pipe 13 and collected in the recovered liquid tank 14.

Note that any one of the first recovered liquid S1, the second recovered liquid S2, and the third recovered liquid S3 may be recovered in the recovered liquid tank 14, but all the recovered liquids S1 to S3 are stored. By collecting, the recovery rate of the glass component from the exhaust gas can be increased. Further, it is preferable that the recovered liquid tank 14 recovers the recovered liquid after being treated with water and Mg (OH) ₂ . That is, it is preferable that the first contact liquid L1 and the second contact liquid L2 are liquids that contain water and Mg (OH) ₂ .

In the example shown in FIG. 2, the second cooling tower 4 is provided together with the first cooling tower 2, but the second cooling tower can be omitted by sufficiently cooling the exhaust gas by the first cooling tower. In this case, the exhaust gas may be brought into contact with water and Mg (OH) ₂ in the scrubber 6.

“5. Reuse of recovered liquid”
In the present embodiment, the recovered liquid is used as a cooling liquid in the process of cooling the exhaust gas.

In FIG. 2, the recovered liquid tank 14 from which the recovered liquid is recovered includes a pH measurement device 15 and an Mg (OH) ₂ addition device 16. The first to third recovered liquids S1 to S3 are mixed in the recovered liquid tank 14 to become a recovered liquid mixture. In this recovered liquid mixture, at least a boron component in the exhaust gas G0 is dissolved. In the recovered liquid tank 14, Mg (OH) ₂ is added to the recovered liquid mixture. Thereby, the liquid containing a boron component and a magnesium component is obtained.

It is believed that the addition of Mg (OH) ₂ causes the boron component in the recovered liquid mixture to react with Mg (OH) ₂ to produce magnesium borate. The liquid obtained by adding Mg (OH) ₂ contains the produced magnesium borate and, optionally, an unreacted boron component and Mg (OH) ₂ . This liquid is called a liquid containing a boron component and a magnesium component.

The liquid containing the boron component and the magnesium component is preferably an aqueous solution in which these components are dissolved. In addition, components in the liquid such as magnesium borate are not sufficiently dissolved due to changes in the concentration, liquid temperature, liquid pH, etc., and the addition of Mg (OH) ₂ to the recovered liquid mixture may cause some cloudiness. is there. However, even the liquid in a state in which the cloudiness is generated can be used as various liquids for the first cooling tower 2, the second cooling tower 4, and the scrubber 6.

Further, when the glass melted in the glass melting furnace 1 is an alkali-free glass, the liquid obtained by adding Mg (OH) ₂ may contain a trace amount of chlorine, fluorine, calcium, and the like.

In addition, since Mg (OH) ₂ is hardly soluble in water, in the Mg (OH) ₂ addition device 16, a slurry in which Mg (OH) ₂ is dispersed in water (hereinafter referred to as a water slurry of Mg (OH) ₂ is referred to. It is preferred to prepare and add this to the recovered liquid mixture. The Mg _(OH) of Mg _{(OH) 2} in ₂ water slurry concentration may be constant or may be changed according to the water level in the collection liquid tank 14.

In addition, in the liquid to which the aqueous slurry of Mg (OH) ₂ is added, a stirring means such as a bubbler is provided in the recovery liquid tank 14 in order to prevent generation of precipitates or white turbidity due to unreacted Mg (OH) _2. It is preferable to provide and stir this liquid.

In the recovered liquid tank 14, the amount of Mg (OH) ₂ added to the recovered liquid mixture is preferably sufficient to convert a boron component such as boric acid in the recovered liquid mixture into a magnesium salt. When the recovered liquid mixture contains a sulfur component and / or a chlorine component, the amount is preferably sufficient to convert these components and the boron component into a magnesium salt.

On the other hand, when the supply amount of Mg (OH) ₂ is too large, precipitation of unreacted Mg (OH) ₂ occurs in the liquid. When such a large amount of precipitation occurs, it is difficult to reuse this liquid as the cooling liquid, the first contact liquid L1, or the second contact liquid L2, which is not preferable.

Accordingly, the pH of the liquid in the recovered liquid tank 14 is measured by the pH measuring device 15, and the supply amount of the aqueous slurry of Mg (OH) ₂ is maintained so that this pH is maintained within the range of 6.5 to 7.7. Is preferably controlled. When the pH of this liquid is 6.5 or more, the boron component and the like in the recovered liquid mixture can be favorably converted into a magnesium salt, and the unreacted boron component and the like remaining in the liquid can be reduced.

On the other hand, in order to satisfactorily prevent precipitation or white turbidity due to Mg (OH) _{2 in the} liquid, the pH of the liquid is preferably maintained at 7.7 or less, more preferably 7.5 or less, 7.0 or less is particularly preferable.

The liquid thus obtained is supplied from the recovery liquid tank 14 to the first cooling tower 2 and reused as a cooling liquid.

In this embodiment, a part of this liquid may be reused as the first contact liquid L1 and the second contact liquid L2. That is, a part of the liquid in the recovered liquid tank 14 passes through the circulation pump 17 and is temperature-adjusted as necessary, and then sprayed into the second cooling tower 4 and the scrubber 6. It can be used as the second contact liquid L2 sprayed on.

<Recovered powder>
Next, the collected powder collected by the bag filter 3 will be described. The recovered powder has an average particle size (D50) of 30 to 100 μm.

According to this embodiment, since the alkali metal is not added in the system, the recovered powder can be used as a glass raw material for producing an alkali-free borosilicate glass. The recovered powder can be reused as a glass raw material after being recovered from the bag filter 3 and put into the glass melting furnace 1 on the same line. The recovered powder may be taken out from the bag filter 3 for use in another glass production line after being recovered.

This recovered powder has a melting point of 100 ° C. or higher than soda lime glass containing an alkali component, and is added to the glass raw material when the alkali-free glass raw material that is hardly soluble is melted in the glass melting furnace 1. Suitable for By adding this recovered powder to the alkali-free glass raw material, the solubility can be improved and the clarity can be improved. Thereby, high productivity and high quality alkali-free glass can be obtained.

The recovered powder may contain boron components, sulfur components, chlorine components, fluorine components, etc. contained in the exhaust gas G0 as components recovered by the bag filter 3. Further, the recovered powder may contain a calcium component added from the Ca compound supply device 18. Further, the recovered powder may include a magnesium component, a boron component, a sulfur component, a chlorine component, and the like as components added to the first cooling tower 2 from the recovered liquid tank 14.

The recovered powder preferably has a MgO / (CaO + MgO) ratio of 0.1 to 1.0, more preferably 0.1 to 0.8, and still more preferably 0.1 by mass ratio based on oxide. ~ 0.4. This can provide a composition that can be easily reused as a glass raw material.

When the fluorine component is contained in the exhaust gas G0 as a clarifier component, the fluorine component is adsorbed on the calcium component by the bag filter 3 and can be recovered together as a recovered powder.

In the recovered powder, the fluorine component is preferably 0.1 to 2.0% by mass, more preferably 0.3 to 1.0% by mass, based on the oxide, with respect to the entire powder. Thereby, when reusing as a glass raw material, the composition containing a fluorine as a clarifier can be provided. Examples of the fluorine component contained in the recovered powder include calcium fluoride and magnesium fluoride.

When using fuel such as heavy oil in the glass melting furnace 1, sulfur components may be mixed into the exhaust gas G0. In this case, sulfur components may be circulated and concentrated in the exhaust gas treatment system. In this case, when the recovered powder is reused as a glass raw material, the blending amount may be adjusted in consideration of the increase in the sulfur component.

On the other hand, in the case of using a fuel with a low sulfur component content in the glass melting furnace 1, it is possible to prevent the sulfur component from being concentrated, so that the entire recovered powder can be reused as a glass raw material. Is possible.

In this case, the volume concentration of the sulfur oxide gas in the exhaust gas G0 collected from the glass melting furnace 1 is 500 vol. It is preferable to melt the glass raw material so as to be equal to or lower than ppm, and more preferably 50 vol. More preferably, it is not more than ppm, and further substantially does not contain sulfur oxide gas. Examples of such a melting method include gas combustion and electric heating.

Here, examples of the sulfur oxide gas in the exhaust gas G0 include SO ₃ and SO ₂ .

[Particle size of recovered powder]
The lower limit of the average particle diameter (D50) of the recovered powder may be 30 μm or more, more preferably 35 μm or more, and further preferably 40 μm or more. On the other hand, the upper limit value may be 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less.

When the recovered powder is used in a method of melting by a normal melting method, the average particle size (D50) is preferably 100 μm or less from the viewpoint of easily suppressing the generation of bubbles in the molten glass.

The volume-based 90% cumulative particle size (D90) of the recovered powder is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less, and even more preferably 80 μm or less.

The above average particle diameter (D50) and volume-based 90% cumulative particle diameter (D90) can be adjusted by the type, thickness, air permeability, etc. of the bag cloth of the bag filter 3.

Here, the average particle diameter (D50) is a median diameter of 50% cumulative volume in a particle size distribution curve measured using a laser diffraction scattering method when the particles are less than 1 mm.

The volume-based 90% cumulative particle diameter (D90) is a particle diameter of 90% cumulative volume in a particle size distribution curve measured using a laser diffraction scattering method when the particles are less than 1 mm.

[Granulated body]
The recovered powder recovered by the present embodiment may be provided as a granulated body. As a manufacturing method of a granulated body, it can granulate by mixing powder and arbitrary liquids and using a well-known granulation method suitably. For example, a dry granulation method such as rolling granulation or a wet granulation method such as spray drying is preferably used. By using the first to third recovery liquids S1 to S3 as the liquid to be mixed with the powder, the glass raw material recovery rate from the exhaust gas can be increased.

Moreover, since the alkaline powder metal component and the boric acid component are contained in the recovered powder, an alkaline earth metal borate hydrate can be generated in the granulated body. By containing the alkaline earth metal borate hydrate in the granulated body, the strength of the granulated body can be improved. As the alkaline earth metal, Ca and / or Sr are preferable. In particular, Ca is a component added in the powder recovery process, and thus is included in the recovered powder. By adding this Ca component in the form of dolomite ((Ca, Mg) CO ₃ ), calcium borate hydrate can be more easily generated.

Moreover, when the recovered powder contains a magnesium component, the strength of the granulated body can be improved when the granulated body is formed. Since Mg is a component added in the second cooling tower 4 and the scrubber 6, it is contained in the recovered powder.

<Glass product manufacturing method>
According to this embodiment, it can obtain as a final product by shape | molding the molten glass obtained in the above-mentioned glass manufacturing method, and cooling it slowly. In addition, the final product of glass is a product in which glass that is solid at room temperature and has substantially no fluidity is used for part or all of the glass, and the glass surface is processed. .

FIG. 3 is a flowchart showing an example of the glass manufacturing method of the present embodiment. Reference numeral 101 denotes a glass melting step, which corresponds to the glass melting step described above.

First, the molten glass obtained in the glass melting step 101 is formed into a target shape in the forming step 102 and then slowly cooled in a slow cooling step 103 by a known method. Thereafter, the glass is obtained by performing post-processing by a known method such as cutting or polishing in the post-processing step 104 as necessary.

The forming step 102 can be performed by a known method such as a float method, a down draw method, or a fusion method. The float process is a method of forming molten glass into a plate shape on molten tin. In the present embodiment, the molten glass is preferably formed into a plate shape by a float method or the like.

Although the present 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. 2012-250944 filed on November 15, 2012, the contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1 Glass melting furnace 2 1st cooling tower 3 Bag filter 4

2nd cooling tower

5, 11, 12, 13 Pipe 6 Scrubber 7 High differential pressure part 8 Centrifugal dust collector 9 Fan 10 Chimney 14 Recovery liquid tank 15 pH measuring device 16 Mg (OH) ₂ addition device 17 circulating pump 18 Ca compound supply device 19 recovered powder tanks G0, G1, G2 exhaust gas G3 cooled exhaust gas G4 clean gas G5 exhaust clean gas L1 first contact liquid L2 second contact liquid S1 First recovered liquid S2 Second recovered liquid S3 Third recovered liquid 101 Glass melting step (granulated material melting step)
102 Molding process 103 Gradual cooling process 104 Post-processing process 1001 Glass melting / exhaust gas collection process 1002 Exhaust gas cooling process 1003 Powder recovery process 1004 at the dust collecting member Liquid recovery process 1005 with Mg (OH) ₂ and water Exhaust process

Claims

By mass percentage based on oxide, SiO 2 : 50 to 73%, Al 2 O 3 : 10.5 to 24%, B 2 O 3 : 0.1 to 12%, MgO: 0.5 to 10%, CaO : 0.5 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, ZrO 2 : 0 to 5%, Cl: 0.01 to 0.35%, F: 0.01 Manufactures alkali-free glass containing ˜0.15% and SO 3 : 0.0001˜0.0025%, MgO + CaO + SrO + BaO: 8˜29.5%, MgO / (MgO + CaO): 0.1˜0.8 A way to
A process of melting glass raw material and collecting exhaust gas,
Cooling the exhaust gas by bringing a cooling liquid into contact with the exhaust gas,
One or more selected from the group consisting of CaCO 3 , Ca (OH) 2 and (Ca, Mg) CO 3 is added to the cooled exhaust gas, and an average particle diameter (D50) from the exhaust gas using a dust collecting member Recovering a powder of 30 to 100 μm, and contacting the exhaust gas from which the powder is recovered with Mg (OH) 2 and water to recover the components contained in the exhaust gas as a recovery liquid,
The recovered liquid is used as the cooling liquid in the step of cooling the exhaust gas.
A method for producing alkali-free glass.
The method for producing alkali-free glass according to claim 1, wherein the powder collected using the dust collecting member is added to the glass raw material and melted.
The method for producing an alkali-free glass according to claim 1 or 2, wherein the powder recovered using the dust collecting member has an MgO / (CaO + MgO) ratio of 0.1 to 1.0 based on an oxide-based mass ratio. .
The step of recovering powder using the dust collecting member is alkali-free according to any one of claims 1 to 3, wherein a fluorine component contained in the exhaust gas after powder recovery is 30 mg / Nm 3 or less. Glass manufacturing method.
The alkali-free glass production according to any one of claims 1 to 4, wherein the powder collected using the dust collecting member has a fluorine component of 0.1 to 2.0 mass% based on oxides. Method.
The method for producing alkali-free glass according to any one of claims 1 to 5, wherein the powder collected using the dust collecting member has a volume-based 90% cumulative particle diameter (D90) of 200 µm or less.
The glass material has a sulfur oxide gas concentration of 500 vol. The manufacturing method of the alkali free glass of any one of Claim 1 to 6 fuse | melted so that it may become ppm or less.
The method for producing alkali-free glass according to any one of claims 1 to 7, wherein a boron component is recovered from the exhaust gas.
The method for producing an alkali-free glass according to any one of claims 1 to 8, wherein the glass has an alkali metal oxide content of 1% or less in terms of a mass percentage based on the oxide.
The method for producing alkali-free glass according to any one of claims 1 to 9, wherein the molten glass is formed into a plate shape after melting the glass raw material.