JP7684631B2 - Glass article manufacturing method and glass article manufacturing device - Google Patents

Description

The present invention relates to an improvement to a method for manufacturing glass articles and an apparatus for manufacturing glass articles.

In a glass melting furnace, powdered or granular glass raw material is heated by a burner that burns fuel (e.g., hydrocarbon gas such as natural gas) or by passing electricity between electrodes to produce molten glass. This molten glass goes through a specific forming process to become various glass products such as glass sheets, glass tubes, and glass fibers.

At this time, the exhaust gas generated from the glass melting furnace contains some of the components contained in the glass raw materials in the form of gas or fine solids. For this reason, the exhaust gas also contains many components that can be recycled as glass raw materials. Therefore, if recycled raw materials can be recovered from the exhaust gas, it can contribute to saving glass raw materials. At the same time, it can also be environmentally friendly.

As one such method, for example, Patent Document 1 discloses a technology for recovering recycled materials containing boron from exhaust gas of a glass melting furnace that melts glass raw materials containing boron. In detail, when the exhaust gas discharged from the glass melting furnace is cooled by spraying cooling water in a spray tower, the boron contained as a gas in the exhaust gas precipitates as a solid (dust) and is collected in the cooling water (collection liquid). The boron that passes through the spray tower comes into contact with water from a wet electrostatic precipitator and is collected in the water (collection liquid). A neutralizing agent such as hydrated lime is added to this collection liquid containing boron, and processing such as removing impurities is performed, thereby recovering boron as a recycled material (see Patent Document 1).

JP 2013-180284 A

However, when recovering boron using wet equipment that uses spray towers or wet electrostatic precipitators, large-scale wastewater treatment equipment is required, which increases power consumption, resulting in higher running costs and higher initial costs.

The objective of the present invention is to efficiently recover dust from exhaust gas discharged from a glass melting furnace at low cost.

A method for manufacturing a glass article, comprising a melting process for heating glass raw materials in a melting furnace to obtain molten glass, a forming process for forming the molten glass into a glass article, and an exhaust gas treatment process for removing dust from exhaust gas discharged from the melting furnace, wherein the melting process comprises an electric heating process for melting the glass raw materials by electric heating mainly using electrodes, the exhaust gas treatment process comprises a dry collection process for treating the exhaust gas discharged from the melting furnace during the electric heating process, and the dry collection process comprises a dry cooling process for mixing a cooling gas with the exhaust gas, and a dry separation process for separating the dust from the exhaust gas that has been subjected to the dry cooling process using a dry separation device.

Electric heating and combustion heating are used as heating means for melting glass raw materials in a melting furnace. Electric heating is a method of heating molten glass by passing electricity between electrodes immersed in molten glass. Combustion heating is a method of heating glass raw materials and molten glass by burning fuel in a melting furnace. The exhaust gas generated by electric heating contains a lower proportion of water vapor than the exhaust gas generated by combustion heating. If the proportion of water vapor in the exhaust gas is high, clogging is likely to occur in dry separation devices such as bag filters, and maintenance costs may increase. Therefore, if the electric heating process melts glass raw materials mainly by electric heating using electrodes, the proportion of water vapor in the exhaust gas is low, so clogging can be suppressed and maintenance costs can be reduced. In addition, exhaust gas treatment is possible without using spray towers, wet electric dust collectors, wastewater treatment equipment, or chemicals such as neutralizing agents, and dust can be efficiently collected from the exhaust gas at low cost.

In the above configuration, the dry separation device is preferably a bag filter. With this configuration, dust can be collected from the exhaust gas at a lower cost.

In the above configuration, the melting process includes at least a combustion heating process for melting the glass raw material by combustion heating using a burner, and the exhaust gas treatment process includes a wet collection process for treating the exhaust gas discharged from the melting furnace during the combustion heating process, and the wet collection process preferably includes a wet cooling process for spraying a cooling liquid into the exhaust gas. The exhaust gas discharged from the melting furnace performing the combustion heating process contains a high proportion of water vapor. The wet collection process can treat exhaust gas containing a high proportion of water vapor without any problems. Therefore, when performing combustion heating, the wet collection process can be performed to efficiently treat the exhaust gas. The combustion heating process and the wet collection process are performed temporarily, for example, when the melting furnace is started up, and the spray tower or the like is not used all the time as in Patent Document 1. Therefore, it is possible to share the spray tower or the like with other melting furnaces or to reduce its size, thereby reducing running costs and initial costs.

In the above configuration, it is preferable that the wet collection process includes a wet separation process in which the dust is separated from the exhaust gas that has been subjected to the wet cooling process using a wet separation device. With this configuration, dust can be more reliably collected from the exhaust gas.

In the above configuration, the wet separation device is preferably a wet electrostatic precipitator. With this configuration, dust can be collected from the exhaust gas more reliably and at lower cost.

In the above configuration, it is preferable that the temperature of the exhaust gas after the dry cooling process is 60°C or less. With this configuration, components contained in the exhaust gas in a gaseous state can be precipitated as solids and recovered in the dry separation process.

In the above configuration, it is preferable that the volume fraction of water vapor contained in the exhaust gas discharged from the melting furnace during the electrical heating process is 10% or less. With this configuration, the water vapor contained in the exhaust gas does not condense even after the dry cooling process, and the dry collection process can be carried out efficiently.

In the above configuration, it is preferable that the glass raw material contains boron, and the exhaust gas treatment process includes a recovery process for recovering boron from the dust. With such a configuration, the recovered boron can be reused as a glass raw material. Note that "boron" here includes boron compounds such as boron oxide and boric acid (the same applies below).

In the above configuration, it is preferable that the exhaust gas treatment process includes a denitrification process in which the exhaust gas that has passed through the dry capture process or the wet capture process is subjected to a denitrification process. With this configuration, it is possible to reduce the amount of nitrogen oxides contained in the exhaust gas that flow into the environment.

In the above configuration, the temperature of the cooling gas is preferably 15°C or higher. With this configuration, the components contained in the exhaust gas in a gaseous state can be precipitated as solids. In addition, the exhaust gas that has been through the dry cooling process is not cooled more than necessary, and condensation of water vapor contained in the exhaust gas can be prevented. This makes it possible to prevent clogging of the dry separation device and corrosion of the equipment.

In the above configuration, it is preferable that the cooling gas is heated by exhaust heat from the melting furnace. When the outside air temperature is 15°C or higher, the outside air can be used directly as the cooling gas. On the other hand, when the outside air temperature is less than 15°C, the outside air can be used as the cooling gas by heating it to 15°C or higher to prevent condensation of the water vapor contained in the exhaust gas. By using the exhaust heat from the melting furnace to heat the outside air, the amount of energy used can be reduced.

The glass article manufacturing apparatus according to the present invention is an apparatus for manufacturing glass articles, comprising a melting furnace for heating glass raw materials to obtain molten glass, a forming device for forming the molten glass into a glass article, and an exhaust gas treatment facility for removing dust from exhaust gas discharged from the melting furnace, wherein the melting furnace performs an electric heating process for melting the glass raw materials mainly by electric heating using electrodes, and the exhaust gas treatment facility includes a dry collection facility, which includes a dry cooling device for mixing a cooling gas with the exhaust gas and a dry separation device for separating the dust from the exhaust gas using a bag filter, and the dry collection facility treats the exhaust gas discharged from the melting furnace during the electric heating process. With this configuration, dust can be efficiently collected from the exhaust gas discharged from the glass melting furnace at low cost.

According to the present invention, dust can be efficiently recovered from exhaust gas discharged from a glass melting furnace at low cost.

FIG. 1 is a schematic diagram showing the overall configuration of a method for producing a glass article according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the overall configuration of a glass article manufacturing apparatus according to one embodiment of the present invention.

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

As shown in Figures 1 and 2, the method for manufacturing a glass article according to this embodiment includes a melting process S1, a forming process S2, and an exhaust gas treatment process S3.

In the melting step S1, glass frit Gr adjusted to a predetermined component ratio is supplied to the melting furnace 1 using a raw material input device 11. For example, a screw feeder can be used as the raw material input device 11. In the melting furnace 1, the glass frit Gr is heated to obtain molten glass Gm. As the glass frit Gr and molten glass Gm are heated, exhaust gas Gs is discharged from the melting furnace 1. The melting step S1 includes an electrical heating step S11 and a combustion heating step S12.

The electric heating step S11 is a step of heating the glass frit Gr mainly by electric heating using electrodes not shown. In the electric heating step S11, combustion heating may be used as an auxiliary, but it is preferable to heat the glass frit Gr only by electric heating without using combustion heating. When combustion heating is used as an auxiliary, it is preferable that the ratio of the heat generated by electric heating to the total heat generated by the heat generated by combustion heating and the heat generated by electric heating is 90% or more, from the viewpoint of making the volume fraction of water vapor contained in the exhaust gas Gs preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. The electric heating step S11 of this embodiment is performed during operation, and the glass frit Gr is continuously supplied to the melting furnace 1, and the molten glass Gm is continuously discharged from the melting furnace 1.

The combustion heating step S12 is a step of heating the glass frit Gr by combustion heating using at least a burner. In the combustion heating step S12, the glass frit Gr may be heated only by combustion heating, or the glass frit Gr may be heated supplementarily by electrical heating. The combustion heating step S12 of this embodiment is performed at the start-up before operation. In this case, the glass frit Gr is supplied to the melting furnace 1 continuously or intermittently.

The exhaust gas Gs discharged from the melting furnace 1 contains burner combustion gas and volatile matter from the glass raw material Gr and molten glass Gm. The combustion gas contains carbon dioxide, water vapor, nitrogen oxides, and sulfur oxides. The volatile matter contains boron.

In electrical heating, the molten glass Gm is heated by passing electricity between electrodes immersed in the molten glass Gm. When glass raw material Gr is heated only by electrical heating, the exhaust gas Gs does not contain combustion gas.

For the combustion heating, burners such as air combustion burners and oxygen combustion burners are used. It is preferable to use oxygen combustion burners because they have high heating efficiency and produce a small amount of exhaust gas Gs. As fuel for the burners, gaseous fuels such as natural gas are used. It is preferable that the gaseous fuel contains a small amount of sulfur compounds. This makes it possible to omit the sulfur oxide removal process in the exhaust gas treatment process S3 described below, and prevents deterioration of the exhaust gas treatment equipment 3 due to the generation of sulfurous acid and sulfuric acid.

Electrical heating has the advantages of a small amount of exhaust gas Gs, a small proportion of water vapor contained in the exhaust gas Gs, and good heating efficiency for molten glass Gm. However, because it is difficult for electric current to flow through glass raw material Gr and solidified glass, it is difficult to obtain molten glass Gm by electrical heating when starting up the melting furnace 1 or when restarting the melting furnace 1 after it has been temporarily stopped. For this reason, when starting up and restarting the melting furnace 1, a method is used in which molten glass Gm is obtained initially only by combustion heating, and the proportion of electrical heating is gradually increased.

The molten glass Gm obtained in the melting step S1 is sent to a forming device 2, where the forming step S2 is carried out. In the forming step S2, the molten glass Gm is formed into a glass product Gp of a predetermined shape, such as a glass plate, a glass tube, or glass fiber. For example, when forming into a glass plate, the float method, the overflow downdraw method, the slot downdraw method, the roll-out method, or the like is used.

The exhaust gas Gs discharged from the melting furnace 1 is introduced into the exhaust gas treatment equipment 3, where the exhaust gas treatment process S3 is carried out. The exhaust gas treatment equipment 3 includes a dry capture equipment 31, a wet capture equipment 32, a denitrification equipment 33, and a recovery equipment 34. The exhaust gas treatment process S3 also includes a dry capture equipment S31, a wet capture equipment S32, a denitrification equipment S33, and a recovery process S34.

The exhaust gas Gs11 discharged from the melting furnace 1 performing the electrical heating process S11 is introduced into the dry collection equipment 31, where the dry collection process S31 is performed. The dry collection equipment 31 includes a dry cooling device 311 and a dry separation device 312. The dry collection process S31 also includes a dry cooling process S311 and a dry separation process S312.

The exhaust gas Gs11 introduced into the dry collection equipment 31 is first introduced into the dry cooling device 311, where the dry cooling process S311 is performed. In the dry cooling process S311, the exhaust gas Gs11 at about 80°C to 300°C is mixed with cooling gas Gc to lower the temperature. The temperature of the mixed cooling gas Gc is preferably 15°C or higher, more preferably 20°C or higher. The temperature of the cooled exhaust gas Gs12 is preferably 15°C or higher and 60°C or lower, more preferably 20°C or higher and 40°C or lower. If the temperature of the cooled exhaust gas Gs12 is too low, the water vapor contained in the exhaust gas Gs12 condenses and water droplets are generated. The generated water droplets have adverse effects such as clogging of the bag filter and corrosion of the piping, which will be described later. On the other hand, if the temperature of the exhaust gas Gs12 is too high, the boron contained in the exhaust gas Gs in a gaseous state cannot be precipitated as a solid, and therefore the boron cannot be recovered in the dry separation step S312 described below, and flows out into the atmosphere. Also, when the temperature of the outside air is 15°C or higher, it is preferable to introduce and use the outside air as the cooling gas Gc. When the temperature of the outside air is less than 15°C, it is preferable to heat the outside air using the exhaust heat from the melting furnace 1 and use it as the cooling gas Gc. By using the exhaust heat from the melting furnace 1, it is possible to save energy for maintaining the cooling gas Gc at an optimal temperature.

The exhaust gas Gs12 that has passed through the dry cooling process S311 is introduced into the dry separation device 312, where the dry separation process S312 is carried out. In the dry separation process S312, as the exhaust gas Gs12 passes through the dry separation device 312, dust containing solid boron is separated from the exhaust gas Gs12. As the dry separation device 312, it is preferable to use a bag filter, which can be operated at low cost.

The exhaust gas Gs21 discharged from the melting furnace 1 performing the combustion heating process S12 is introduced into the wet collection equipment 32, where the wet collection process S32 is performed. The wet collection equipment 32 includes a wet cooling device 321 and a wet separation device 322. The wet collection process S32 also includes a wet cooling process S321 and a wet separation process S322. The exhaust gas Gs discharged from the melting furnace 1 performing the combustion heating process S12 contains a high proportion of water vapor, so the water vapor is likely to condense when cooled. For this reason, if a separation process is performed using a filter such as a bag filter, clogging easily occurs, and maintenance costs increase. In order to separate dust containing boron from the exhaust gas Gs while suppressing costs and without being affected by condensation, it is preferable to perform the wet collection process S32.

The exhaust gas Gs21 introduced into the wet collection equipment 32 is first introduced into a wet cooling device 321 (e.g., a spray tower) and a wet cooling process S321 is performed. In the wet cooling process S321, the exhaust gas Gs21 is sprayed with a cooling liquid Lc to lower the temperature. The temperature of the cooled exhaust gas Gs22 is preferably 60°C or higher and 70°C or lower. By lowering the temperature of the exhaust gas Gs22 in this manner, most of the boron contained in the exhaust gas Gs in a gaseous state can be precipitated as a solid and recovered. As the cooling liquid Lc, water or lime water may be used. In addition, a liquid that has captured boron in the wet separation device 322 described later may be used. As the exhaust gas Gs21 comes into contact with the cooling liquid Lc, boron in a solid (dust) state or gaseous state is captured from the exhaust gas Gs21 by the cooling liquid Lc.

The exhaust gas Gs22 that has passed through the wet cooling step S321 is preferably introduced into the wet separation device 322, where the wet separation step S322 is performed. In the wet separation step S322, as the exhaust gas Gs22 passes through the wet separation device 322, boron in a solid (dust) state or gaseous state from the exhaust gas Gs22 comes into contact with the liquid (e.g., water) and is collected in the liquid. As the wet separation device 322, it is preferable to use a wet electrostatic precipitator because of its high performance in separating dust and liquid droplets from the exhaust gas Gs22.

The exhaust gas Gs13 that has passed through the dry capture process S31, and the exhaust gas Gs23 that has passed through the wet capture process S32 are preferably introduced into the denitration equipment 33, where the denitration process S33 is carried out. In the denitration process S33, the exhaust gas Gs13 and the exhaust gas Gs23 are mixed with ammonia as a reducing agent, and then brought into contact with a catalyst to reduce the nitrogen oxides contained in the exhaust gas Gs13 and the exhaust gas Gs23. The exhaust gas Gs3 that has passed through the denitration process S33 is released into the atmosphere via a chimney.

The recovery process S34 is carried out following the dry separation process S312 and the wet separation process S322. The recovery process S34 also includes a dry recovery process S341 for recovering dust D containing boron from the dry separation device 312, and a wet recovery process S342 for recovering boron from the liquid in which boron has been collected. The recovery facility 34 includes a solid-liquid separator 3421 and a dryer 3422.

In the dry recovery step S341, for example, dust D accumulated on a bag filter is brushed off and collected from an outlet (not shown) provided at the bottom of the dry separation device 312. When brushing off the dust D, a vibration method that applies vibrations to the bag filter, a backwash method that applies a reverse airflow, a pulse jet method that instantly sprays compressed air, or other methods can be used. These methods may also be combined. The collected dust D contains boron.

In the wet recovery process S342, boron is recovered from the cooling liquid Lc from which boron has been collected in the wet cooling device 321 and the liquid from which boron has been collected in the wet separation device 322. Hereinafter, the cooling liquid Lc from which boron has been collected in the wet cooling device 321 and the liquid from which boron has been collected in the wet separation device 322 are collectively referred to as the collected liquid Lt. The collected liquid Lt is introduced into the solid-liquid separation device 3421 and separated into the extracted solid Se and the waste liquid Lw. Examples of the solid-liquid separation device 3421 include a filter press, a centrifugal separator, a vacuum filtration, and the like, but the type is not particularly limited. The extracted solid Se is introduced into the dryer 3422 and dried until it has a predetermined moisture content. Examples of the dryer 3422 include a vacuum dryer, a rotary dryer, a band dryer, a spray dryer, and the like, but the type is not particularly limited. The dried extracted solid Se contains boron. The waste liquid Lw is treated and discharged using waste liquid treatment equipment (not shown).

In the dry recovery step S341 and the wet recovery step S342, it is preferable to remove impurities from the dust D or the extracted solid Se to extract boron. For example, if the dust D or the extracted solid Se is mixed with a high-concentration boron solution, the impurities contained in the extracted solid Se will dissolve in the high-concentration boron solution, and the boron contained in the extracted solid Se will remain as undissolved (extracted). The boron thus recovered is used as a boron source for the glass raw material Gr.

The above-mentioned manufacturing method of a glass article includes a dry collection step S31, and the manufacturing apparatus of a glass article includes a dry collection facility 31. Therefore, the manufacturing method and manufacturing apparatus of a glass article of this embodiment can efficiently recover dust from the exhaust gas Gs discharged from the glass melting furnace 1 in which the electric heating step S11 is performed at low cost. In addition, by performing the dry collection step S31 when the electric heating step S11 is performed and the wet collection step S32 when the combustion heating step S12 is performed, it is possible to treat the exhaust gas Gs containing a high proportion of water vapor discharged from the glass melting furnace 1 in which the combustion heating step S12 is performed without any problems. In addition, for example, if the electric heating step S11 and the dry collection step S31 are performed during operation and the combustion heating step S12 and the wet collection step S32 are temporarily performed when the melting furnace 1 is started up, there is no need to use a spray tower or the like all the time as in Patent Document 1. Therefore, it is possible to share the spray tower with other melting furnaces or the like or to reduce the size, thereby reducing running costs and initial costs.

The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects. Various modifications of the present invention are possible without departing from the gist of the present invention.

In the above embodiment, the glass raw material is supplied to the melting furnace using a screw feeder, but this is not limited to this. A vibration feeder or a pusher may also be used. Also, multiple units may be used instead of one unit.

In the above embodiment, a bag filter was used as the dry separation device, but this is not limited to this. A dry electrostatic precipitator or a ceramic filter may be used instead of the bag filter.

In the above embodiment, the wet separation process is performed after the wet cooling process, but this is not limited to the above. If the amount of cooling liquid sprayed in the wet cooling process is small, all of the cooling liquid sprayed into the exhaust gas will evaporate. On the other hand, if the amount of cooling liquid sprayed is sufficiently large, some of the cooling liquid will not evaporate but will remain as droplets, and dust containing boron can be collected in the droplets. In this case, dust can be collected from the exhaust gas without performing the wet separation process.

In the above embodiment, the exhaust gas treatment process includes a denitrification process, but is not limited to this. If the concentration of nitrogen oxides contained in the exhaust gas is low, the denitrification process does not need to be performed.

In the above embodiment, ammonia was used as the reducing agent in the denitrification process, but this is not limited to this. Ammonia water or urea may be used instead of ammonia.

The present invention can be suitably used to recover dust from exhaust gas discharged from a glass melting furnace efficiently and at low cost.

1 Melting furnace 2 Molding device 3 Exhaust gas treatment equipment 31 Dry collection equipment 311 Dry cooling device 312 Dry separation device 322 Wet separation device Gp Glass article Gm Molten glass Gr Glass raw material Gs Exhaust gas Gc Cooling gas Lc Cooling liquid S1 Melting process S11 Electric heating process S12 Combustion heating process S2 Molding process S3 Exhaust gas treatment process S31 Dry collection process S311 Dry cooling process S312 Dry separation process S32 Wet collection process S321 Wet cooling process S322 Wet separation process S33 Denitrification process S34 Recovery process

Claims (11)

A melting step of heating glass raw materials in a melting furnace to obtain molten glass;
forming the molten glass into a glass article;
and an exhaust gas treatment step for removing dust from the exhaust gas discharged from the melting furnace,
The melting step includes an electric heating step of melting the glass raw material by electric heating mainly using electrodes,
The exhaust gas treatment process includes a dry collection process for treating the exhaust gas discharged from the melting furnace during the electric heating process,
The dry collection step includes a dry cooling step of mixing a cooling gas with the exhaust gas, and a dry separation step of separating the dust from the exhaust gas that has been subjected to the dry cooling step by using a dry separation device,
The melting step includes at least a combustion heating step of melting the glass frit by combustion heating using a burner,
The exhaust gas treatment process includes a wet collection process for treating exhaust gas discharged from the melting furnace during the combustion heating process,
The method for manufacturing a glass article , wherein the wet collection step includes a wet cooling step of spraying a cooling liquid into the exhaust gas . The method for manufacturing glass articles according to claim 1, characterized in that the dry separation device is a bag filter. 3. The method for manufacturing a glass article according to claim 1 , wherein the wet collection step includes a wet separation step of separating the dust from the exhaust gas that has been subjected to the wet cooling step by using a wet separation device. The method for manufacturing a glass article according to claim 3 , wherein the wet separation device is a wet electric dust collector. 5. The method for producing a glass article according to claim 1 , wherein the temperature of the exhaust gas having undergone the dry cooling step is 60° C. or lower. The method for manufacturing a glass article according to any one of claims 1 to 5 , characterized in that the volume fraction of water vapor contained in the exhaust gas discharged from the melting furnace during the electrical heating step is 10% or less. The glass frit contains boron,
7. The method for manufacturing a glass article according to claim 1, wherein the exhaust gas treatment step includes a recovery step of recovering boron from the dust. 8. The method for manufacturing a glass article according to claim 1 , wherein the exhaust gas treatment step includes a denitration step of subjecting the exhaust gas that has been subjected to the dry collection step or the wet collection step to a denitration treatment. The method for manufacturing a glass article according to any one of claims 1 to 8 , characterized in that the temperature of the cooling gas is 15°C or higher. The method for producing a glass article according to claim 9 , wherein the cooling gas is heated by exhaust heat from the melting furnace. a melting furnace for heating glass raw materials to obtain molten glass;
a forming device for forming the molten glass into a glass article;
and an exhaust gas treatment facility for removing dust from the exhaust gas discharged from the melting furnace,
The exhaust gas treatment equipment includes a dry collection equipment for treating exhaust gas discharged from the melting furnace during an electric heating process for melting the glass frit mainly by electric heating using electrodes in the melting furnace , and a wet collection equipment for treating exhaust gas discharged from the melting furnace during a combustion heating process for melting the glass frit by combustion heating using at least a burner in the melting furnace ,
The dry collection equipment includes a dry cooling device that mixes a cooling gas with the exhaust gas, and a dry separation device that separates the dust from the exhaust gas using a bag filter,
The apparatus for manufacturing a glass article , wherein the wet collection equipment includes a wet cooling device that sprays a cooling liquid into the exhaust gas .