Exhaust treatment methods and manufacturing methods of glass articles

Abstract

The purpose of this invention is to provide an exhaust gas treatment method that can significantly suppress the problem of neutralizer adhesion on the walls of stabilizers. The exhaust gas treatment method of this invention treats exhaust gas generated during the manufacturing process of glass articles, and includes the following steps: a first step in which exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first treatment gas; a second step in which the first treatment gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second treatment gas; and a third step in which the second treatment gas is contacted with nitrogen oxides (NOx) using a reducing agent; and the cooling aqueous solution used in the first step contains urea or ammonia.

Description

Technical Field

[0001] This invention relates to an exhaust treatment method and a method for manufacturing glass articles. Prior Technology

[0002] During the manufacturing process of glass products, especially during the formation of molten glass, exhaust gases containing hydrogen chloride (HCl), sulfur oxides (SO₄⁻), and nitrogen oxides (NO₃⁻) are sometimes generated. These exhaust gases need to be properly treated before being released into the atmosphere.

[0003] Previously, exhaust treatment equipment was used to treat this type of exhaust. For example, Patent Document 1 describes an exhaust treatment device that includes a stabilizer, a bag filter, and a denitrification device.

[0004] The exhaust gas is cooled in a stabilizer, and a portion of the hydrogen chloride and sulfur oxides contained in the exhaust gas are removed. Furthermore, hydrogen chloride and sulfur oxides contained in the exhaust gas are also removed in a bag filter. In addition, nitrogen oxides contained in the exhaust gas are reduced and removed in a denitrification unit. Therefore, by using this exhaust gas treatment equipment, the exhaust gas can be properly treated.

[0005] Furthermore, in the previous exhaust gas treatment equipment, in order to remove acid from the exhaust gas, a neutralizing agent such as sodium hydroxide aqueous solution was sprayed into the stabilizer to neutralize the acid. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-184308 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] In recent years, with the increase in glass production capacity, the volume of exhaust gas emitted from manufacturing equipment has also tended to increase. Therefore, there is a need to further improve the efficiency of exhaust gas treatment.

[0009] To improve the efficiency of exhaust gas treatment, consider increasing the amount and / or concentration of the neutralizing agent sprayed in the stabilizer.

[0010] However, sodium hydroxide aqueous solution, used as a neutralizing agent, has a high viscosity. Therefore, when a high concentration or large amount of neutralizing agent (sodium hydroxide aqueous solution) is sprayed into the stabilizer, the risk of sodium hydroxide adhering to the wall surface increases. Furthermore, if this adhesion becomes significant, it may block the exhaust flow path.

[0011] The present invention was made in view of this background, and its object is to provide an venting treatment method that can significantly suppress the problem of neutralizer adhesion on the wall surface of a stabilizer. Furthermore, the present invention aims to provide a method for manufacturing glass articles utilizing this venting treatment method.

[0012] [Technical means to solve the problem] This invention provides an exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of glass articles, comprising the following steps: a first step in which the exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first treated gas; a second step in which the first treated gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second treated gas; and a third step in which the second treated gas is contacted with a reducing agent for nitrogen oxides (NOx); wherein the cooling aqueous solution used in the first step contains urea or ammonia. [Effects of the Invention]

[0013] This invention provides an venting treatment method that can significantly suppress the adhesion of neutralizing agents to the walls of stabilizers. Furthermore, this invention provides a method for manufacturing glass articles utilizing this venting treatment method. Simple Explanation of the Diagram

[0014] Figure 1 is a flowchart illustrating an exhaust gas treatment method according to one embodiment of the present invention. Figure 2 is a schematic diagram illustrating an example of the configuration of an exhaust treatment apparatus for implementing an exhaust treatment method according to one embodiment of the present invention. Figure 3 is a flowchart illustrating a method for manufacturing a glass article according to one embodiment of the present invention. Figure 4 is a summary graph showing the results of the ammonia content determination in the exhaust gas obtained in each example. Figure 5 is a summary graph showing the chlorine levels measured at the stabilizer outlet in each example. Figure 6 is a summary graph showing the amount of sulfur dioxide measured at the stabilizer outlet in each example. Figure 7 is a summary graph showing the dechlorination rates obtained in the stabilizers in each example. Figure 8 is a summary graph showing the desulfurization rates obtained in the stabilizers in each example. Figure 9 is a summary graph showing the denitrification rates obtained in the denitrification devices in each example. Implementation

[0015] The following describes one embodiment of the present invention.

[0016] As mentioned earlier, in previous exhaust treatment methods, an aqueous sodium hydroxide solution was used as a neutralizing agent sprayed into the stabilizer. However, the aqueous sodium hydroxide solution has a high viscosity, and when spraying high concentrations or large quantities of the aqueous sodium hydroxide solution, there is an increased risk that the sodium hydroxide will adhere to the walls of the stabilizer.

[0017] Therefore, in one embodiment of the present invention, an exhaust gas treatment method is provided, which treats exhaust gas generated during the manufacturing process of glass articles, comprising the following steps: a first step, wherein the exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first treatment gas; a second step, wherein the first treatment gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second treatment gas; and a third step, wherein the second treatment gas is contacted with a reducing agent for nitrogen oxides (NOx); and wherein the cooling aqueous solution used in the first step contains urea or ammonia.

[0018] In one embodiment of the exhaust treatment method of the present invention, a cooling aqueous solution containing urea or ammonia (hereinafter collectively referred to as "ammonia-containing aqueous solution") is used in the first step.

[0019] The viscosity of urea aqueous solution and ammonia aqueous solution is lower than that of sodium hydroxide aqueous solution. Therefore, in the first step, when using an ammonia-containing aqueous solution as a neutralizing agent, even if the concentration of the ammonia-containing aqueous solution is high and / or the amount is relatively large, the problem of the neutralizing agent adhering to the wall of the stabilizer can be significantly reduced.

[0020] Therefore, the exhaust gas treatment method of one embodiment of the present invention can treat exhaust gas more efficiently than the previous method.

[0021] Furthermore, in one embodiment of the present invention, the ammonia-containing aqueous solution can be used alone or in combination with a sodium hydroxide aqueous solution. In the latter case, a mixed aqueous solution containing urea or ammonia and sodium hydroxide can be used, or the ammonia-containing aqueous solution and the sodium hydroxide aqueous solution can be used separately. Moreover, the latter case can significantly reduce the concentration of the sodium hydroxide aqueous solution and / or the spray volume compared with the case of using sodium hydroxide aqueous solution alone.

[0022] (An exhaust treatment method according to one embodiment of the present invention) Hereinafter, an exhaust treatment method according to one embodiment of the present invention will be described in more detail with reference to the drawings.

[0023] Figure 1 schematically illustrates the flow of an exhaust treatment method according to one embodiment of the present invention.

[0024] As shown in Figure 1, an exhaust gas treatment method according to one embodiment of the present invention includes the following steps: a first step (step S110), in which exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first reaction product and a first treatment gas, wherein the cooling aqueous solution contains urea or ammonia; a second step (S120), in which the first treatment gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second reaction product and a second treatment gas; and a third step (S130), in which the second treatment gas is contacted with nitrogen oxides (NOx) using a reducing agent.

[0025] Figure 2 schematically illustrates an example of the configuration of an exhaust treatment apparatus (hereinafter referred to as "treatment apparatus") for implementing an exhaust treatment method according to one embodiment of the present invention.

[0026] As shown in Figure 2, the processing equipment 100 includes: a melting furnace 110, a stabilizer 120, a bag filter 140, a denitrification device 160, a wet scrubbing device 170, and a chimney 180.

[0027] The melting furnace 110 is used to melt glass raw materials to form molten glass.

[0028] Stabilizer 120 is located downstream of melting furnace 110 and is provided to cool the exhaust gas G generated in melting furnace 110. In addition, stabilizer 120 has one or more nozzles 122 capable of spraying neutralizing agent and a first recovery unit 126 for recovering the product generated by the reaction of exhaust gas G and neutralizing agent (hereinafter referred to as "first reaction product S1").

[0029] A bag filter 140 is disposed downstream of the stabilizer 120. The bag filter 140 is provided to process the process gas (hereinafter referred to as "first process gas") G1 discharged from the stabilizer 120. Furthermore, the bag filter 140 includes: a plurality of body sections 142, a powder supply device 150 for supplying powder to each body section 142, and a second recovery unit 146 for recovering the product generated in the body section 142 (hereinafter referred to as "second reaction product S2").

[0030] Each body section 142 is provided with a filter cloth (not shown) forming a flow path for the first processed gas G1. The filter cloth is made of resin such as polytetrafluoroethylene. The powder supply device 150 has a plurality of powder supply chambers 152, each powder supply chamber 152 being connected to its corresponding body section 142. Furthermore, in the example shown in FIG2, each body section 142 and powder supply chamber 152 is composed of three sections. However, the number of sections is not particularly limited.

[0031] The denitrification device 160 is located downstream of the bag filter 140. The denitrification device 160 is provided to treat the treated gas (hereinafter referred to as "second treated gas") G2 discharged from the bag filter 140. Furthermore, the denitrification device 160 has a reducing agent injection nozzle and a catalyst (neither shown). The catalyst may, for example, contain vanadium pentoxide (V₂O₅).

[0032] A wet scrubbing unit 170 is located downstream of the denitrification unit 160. The wet scrubbing unit 170 has the function of recovering water-soluble components contained in the treated gas (hereinafter referred to as "third treated gas") G3 discharged from the denitrification unit 160. Furthermore, the wet scrubbing unit 170 has a nozzle for spraying liquid and a tank for recovering the discharged liquid (neither shown). The liquid may be, for example, water or an aqueous solution. In addition, the wet scrubbing unit 170 may be connected to a piping 174 for returning the discharged liquid recovered to the tank to the stabilizer 120. Alternatively, the wet scrubbing unit 170 may be omitted from the treatment equipment 100.

[0033] Chimney 180 is provided for discharging the treated gas (hereinafter referred to as "fourth treated gas") G4 from the wet scrubbing unit 170 into the atmosphere. However, when the treatment equipment 100 does not have a wet scrubbing unit 170, the third treated gas G3 from the denitrification unit 160 is introduced into chimney 180.

[0034] Hereinafter, with reference to FIG2, each step of an exhaust treatment method (hereinafter referred to as "the first method") according to an embodiment of the present invention will be described.

[0035] (Step S110) First, glass raw materials are melted in melting furnace 110 to form molten glass. During the melting of the glass raw materials, exhaust gas G is generated. This exhaust gas G contains various components, including chlorine, sulfur, and nitrogen. The chlorine component is mainly hydrogen chloride (HCl), the sulfur component is mainly sulfur oxides (SO₄⁻), and the nitrogen component is mainly nitrogen oxides (NO₃⁻). Exhaust gas G cannot be directly discharged; therefore, it is appropriately treated as follows.

[0036] Exhaust gas G is supplied to stabilizer 120. Exhaust gas G is cooled by passing through stabilizer 120. The inlet temperature of stabilizer 120 is, for example, in the range of 700°C to 900°C, and the outlet temperature is, for example, in the range of 200°C to 220°C.

[0037] Furthermore, as mentioned above, one or more nozzles 122 are provided in the stabilizer 120, and an aqueous cooling solution serving as a neutralizing agent is sprayed from these nozzles 122. The neutralizing agent comprises an "ammonia-containing aqueous solution," that is, an aqueous solution containing urea or ammonia. The "ammonia-containing aqueous solution" has a low viscosity, which makes it less likely to cause the aforementioned problem, that is, less likely to cause the neutralizing agent to adhere to the inner wall of the stabilizer 120. Therefore, a higher concentration of the ammonia-containing aqueous solution or a relatively large amount of the ammonia-containing aqueous solution can be used.

[0038] Furthermore, compared to the sodium hydroxide aqueous solution, the "ammonia-containing aqueous solution," as the first reaction product S1 generated by the reaction with exhaust gas G, is less likely to adhere to the inner wall of the stabilizer 120. Specifically, the "ammonia-containing aqueous solution" reacts with the chlorine and sulfur components contained in exhaust gas G to generate ammonium chloride and ammonium sulfate (see reaction formulas (1) to (4) described below). On the other hand, the sodium hydroxide aqueous solution reacts with the chlorine and sulfur components contained in exhaust gas G to generate sodium chloride and sodium sulfate (see reaction formulas (5) and (6) described below). Moreover, compared to the first reaction product S1 containing sodium chloride and sodium sulfate, the first reaction product S1 containing ammonium chloride and ammonium sulfate has a smaller particle size and better flowability, and therefore is less likely to adhere to the inner wall of the stabilizer 120.

[0039] The concentration of urea or ammonia in the cooling aqueous solution is preferably 3% to 30% by mass. When the concentration of urea or ammonia is 3% by mass or higher, it can effectively treat hydrogen chloride (HCl) and sulfur oxides (SO₄⁻) contained in the exhaust gas G. When the concentration of urea or ammonia is below 30% by mass, the viscosity of the cooling aqueous solution is low, making it less likely for the neutralizing agent to adhere to the inner wall of the stabilizer 120. The concentration of urea or ammonia is more preferably 5% to 25% by mass.

[0040] The cooling aqueous solution preferably contains sodium hydroxide or magnesium hydroxide. In this case, the concentration of sodium hydroxide or magnesium hydroxide is more preferably 2.0% by mass or less, and more preferably 1.0% by mass or less. At concentrations above this, the viscosity of the cooling aqueous solution increases, which may cause problems with adhesion to the wall surface.

[0041] Furthermore, the mole ratio (hereinafter referred to as "urea addition rate") of the total amount of urea added to the sprayed neutralizing agent (cooling aqueous solution) relative to the total amount of alkali added is preferably 20% or more, and more preferably 30% or more. Here, the total amount of alkali added refers to the total mole number of urea, ammonia, sodium hydroxide, and magnesium hydroxide added to the neutralizing agent. When the urea addition rate is 20% or more, hydrogen chloride (HCl) and sulfur oxides (SOx) contained in exhaust gas G can be effectively treated.

[0042] Furthermore, the molar ratio (hereinafter referred to as "ammonia addition rate") of the total ammonia added to the sprayed neutralizing agent (cooling aqueous solution) relative to the total alkali added is preferably 30% or more, and more preferably 50% or more. When the ammonia addition rate is 30% or more, hydrogen chloride (HCl) and sulfur oxides (SOx) contained in the exhaust gas G can be effectively treated.

[0043] Furthermore, different neutralizing agents can be sprayed from each nozzle 122. Alternatively, the same neutralizing agent can be sprayed from each nozzle 122. For example, one nozzle 122 can be used for spraying an ammonia-containing aqueous solution, and another nozzle 122 can be used for spraying a sodium hydroxide aqueous solution. Alternatively, a mixed aqueous solution containing urea or ammonia and sodium hydroxide can be sprayed from a single nozzle 122.

[0044] The sprayed neutralizing agent is vaporized within stabilizer 120 and comes into contact with the chlorine and sulfur components contained in the exhaust gas G. As a result, a first reaction product S1 and a first treated gas G1 are generated.

[0045] For example, when the neutralizing agent contains urea, it is believed that hydrogen chloride and sulfur oxides are separated from exhaust gas G by the following reaction formulas (1) and (2). 2HCl+(NH 2) 2CO+H 2O=2NH 4Cl+CO 2(1) SO 3+(NH 2) 2CO+2H 2O=(NH 4) 2SO 4+CO 2(2) Furthermore, when the neutralizing agent contains ammonia, it is believed that hydrogen chloride and sulfur oxides are separated from the exhaust gas G by the following reaction formulas (3) and (4). HCl + NH₃ = NH₄Cl (3) SO 3+2NH 3+H 2O=(NH 4) 2SO 4(4) Furthermore, when the neutralizing agent contains sodium hydroxide, it is believed that hydrogen chloride and sulfur oxides are separated from the exhaust gas G by the following reaction formulas (5) and (6). HCl + NaOH = NaCl + H₂O (5) SO₃ + 2NaOH = Na₂SO₄ + H₂O (6) In this manner, a portion of the chlorine and sulfur components are removed from the exhaust gas G in the form of the first reaction product S1 via the stabilizer 120, and the first treated gas G1 is discharged.

[0046] The first reaction product S1 generated is recovered using the first recovery unit 126.

[0047] (Step S120) Next, the first processing gas G1 discharged from the stabilizer 120 is supplied to the body 142 of the bag filter 140. The temperature of the body 142 is, for example, in the range of 180°C to 220°C. As mentioned above, the body 142 is connected to each powder supply chamber 152 of the powder supply device 150, and powder is supplied from the powder supply chambers 152 to the body 142.

[0048] The powder is composed of alkali metal salts and / or alkaline earth metal salts. The alkali metal salt is preferably sodium bicarbonate or sodium carbonate. The alkaline earth metal salt is preferably calcium hydroxide, calcium carbonate, or a double salt of calcium carbonate and magnesium carbonate. Furthermore, in this specification, alkaline earth metal salts include hydroxides of alkaline earth metals.

[0049] The powder supplied to the main body 142 comes into contact with the chlorine and sulfur components contained in the first processing gas G1. As a result, a second reaction product S2 and a second processing gas G2 are generated. For example, when the powder contains calcium hydroxide, hydrogen chloride and sulfur oxides are separated from the first processing gas G1 by the following reaction formulas (7) and (8), respectively. 2HCl+Ca(OH) 2=CaCl 2+2H 2O (7) SO₃ + Ca(OH)₂ = CaSO₄ + H₂O (8) In this manner, a portion of the chlorine and sulfur components are removed from the first processed gas G1 as a second reaction product S2 via a bag filter 140, and the second processed gas G2 is discharged. The second reaction product S2 is recovered using a second recovery unit 146.

[0050] Here, as shown in reaction formula (1) above, the first processed gas G1 contains ammonium chloride (NH4Cl) generated by reaction in step S110. In bag filter 140, the ammonium chloride reacts with the supplied powder (calcium hydroxide) as shown in reaction formula (9) below, thereby converting it into calcium chloride and ammonia. 2NH 4Cl+Ca(OH) 2=CaCl 2+2NH 3+2H 2O (9) Therefore, when calcium hydroxide is used as a powder, it is assumed that the second processing gas G2 contains ammonia generated by the reaction. This ammonia can then be used in the subsequent step S130.

[0051] Furthermore, as shown in reaction formula (9), when the powder supplied to the bag filter 140 is calcium hydroxide, the supplied calcium hydroxide is also consumed during the formation of ammonia. It is known that most of the calcium hydroxide supplied to the bag filter 140 usually remains in an unreacted state. However, in the first method, for example, by means of reaction formula (9), the amount of calcium hydroxide remaining in the bag filter 140 in an unreacted state can be significantly suppressed. Therefore, the powder supplied to the bag filter 140 can be utilized more efficiently.

[0052] The concentration of sulfur in the second treated gas G2 discharged from the bag filter 140, converted to sulfur dioxide (SO2), is, for example, 100 mg / Nm3 or less. Also, the concentration of chlorine in the second treated gas G2, converted to hydrogen chloride (HCl), is, for example, 100 mg / Nm3 or less.

[0053] (Step S130) Next, the second processed gas G2 discharged from the bag filter 140 is supplied to the denitrification unit 160.

[0054] Furthermore, the second processing gas G2 can be heated before being supplied to the denitrification unit 160. By heating the second processing gas G2, the reaction efficiency within the denitrification unit 160 can be improved. The heating temperature can be, for example, in the range of 250°C to 300°C.

[0055] When the second processing gas G2 is supplied to the denitrification unit 160, a reducing agent is injected through the injection nozzle. The reducing agent is preferably ammonia, ammonia water, or an aqueous urea solution. When the second processing gas G2 comes into contact with the reducing agent (ammonia or ammonia water), for example, the reactions shown in the following reaction formulas (10) and (11) occur. NO + NO₂ + 2NH₃ = 2N₂ + 3H₂O (10) SO 3+2NH 3+H 2O=(NH 4) 2SO 4(11) In this way, nitrogen oxides and sulfur oxides in the second processing gas G2 are removed, and the third processing gas G3 is generated.

[0056] Furthermore, as mentioned above, the second processing gas G2 sometimes contains ammonia (refer to reaction formula (9)). This ammonia can be used to react with nitrogen oxides and sulfur oxides. In this case, the amount of reducing agent supplied from the injection nozzle can be suppressed in the denitrification unit 160.

[0057] The temperature of the third treated gas G3 discharged from the denitrification unit 160 is, for example, in the range of 250°C to 300°C. Furthermore, the concentration of nitrogen oxides contained in the third treated gas G3 is, for example, below 800 mg / Nm³.

[0058] Then, as needed, the third treatment gas G3 discharged from the denitrification unit 160 can be supplied to the wet scrubbing unit 170. By using the wet scrubbing unit 170, residual sulfur and chlorine components that could not be removed in the upstream unit are removed. Specifically, when the third treatment gas G3 is supplied to the wet scrubbing unit 170, a liquid such as water is sprayed from a nozzle. Here, the sulfur and chlorine components dissolve in the water, thus allowing these residual components to be recovered into a tank. The aqueous solution recovered into the tank can be returned to the stabilizer 120 via piping 174. In this case, the amount of wastewater discharged can be reduced.

[0059] Then, the fourth treatment gas G4 discharged from the wet scrubbing unit 170 is released into the atmosphere through the chimney 180. To prevent condensation, the fourth treatment gas G4 may also be supplied to the chimney 180 after being heated to 200°C to 250°C.

[0060] However, as mentioned above, the wet scrubbing unit 170 is not a necessary component and can be omitted. In this case, the third treatment gas G3 from the denitrification unit 160 is directly supplied to the chimney 180, or heated before being supplied to the chimney 180 to prevent condensation.

[0061] The above describes how, through this step in the first method, exhaust gas G can be appropriately processed. Taking the first method as an example, an exhaust gas processing method according to one embodiment of the present invention has been described.

[0062] However, the above description is only one example, and the exhaust gas treatment method of one embodiment of the present invention may also have other steps. For example, the second reaction product S2 recovered by the second recovery unit 146 in step S120 of the first method can be returned to the melting furnace 110 and melted together with the glass raw material. In this case, the amount of waste discharged from the processing equipment 100 can be significantly reduced. In addition, modifications, changes, and additions to each step can be made.

[0063] (A method for manufacturing a glass article according to one embodiment of the present invention) Next, a method for manufacturing a glass article according to one embodiment of the present invention will be described with reference to FIG3. FIG3 schematically illustrates the flow chart of a method for manufacturing a glass article according to one embodiment of the present invention.

[0064] As shown in Figure 3, a method for manufacturing a glass article according to one embodiment of the present invention (hereinafter referred to as the "manufacturing method") includes the following steps: melting glass raw materials to form molten glass (S210); shaping the molten glass to form shaped glass (S220); and slowly cooling the shaped glass to obtain a glass article (S230).

[0065] The following is a description of each step.

[0066] (Step S210) First, the glass raw material is melted using the melting furnace 110 shown in Figure 2 above, thereby forming molten glass.

[0067] (Step S220) Next, the molten glass is shaped. There are no particular restrictions on the shaping method; the methods mentioned earlier can be used. For example, a float glass method or a melting glass method can be used to shape the glass ribbon.

[0068] (Step S230) Next, the shaped glass is slowly cooled to room temperature. Then, the slowly cooled glass is cut to the desired size, thereby producing a glass article.

[0069] Here, during the implementation of the manufacturing method, particularly in the process of forming molten glass (step S210), exhaust gas is generated. This exhaust gas is treated using an exhaust gas treatment method according to one embodiment of the present invention. For example, the exhaust gas can be treated using the aforementioned first method. By treating the exhaust gas using the exhaust gas treatment method according to one embodiment of the present invention, the chlorine, sulfur, and nitrogen components contained in the exhaust gas can be appropriately removed.

[0070] There are no particular restrictions on the composition of the glass articles to be manufactured. However, the manufacturing method is suitable for the manufacture of alkali-free glass for the following reasons. Alkali-free glass refers to glass in which the total content of alkali metal oxides is less than 0.1% by mass.

[0071] In the manufacture of alkali-free glass, in step S210, glass raw materials containing a chlorine-containing clarifying agent are added to the melting furnace 110 to remove air bubbles contained in the molten glass. Therefore, during the manufacturing process of alkali-free glass, exhaust gas containing the corresponding chlorine component may be generated.

[0072] Therefore, in the manufacturing method, an ammonia-containing aqueous solution that does not easily adhere to the wall surface is used as a cooling aqueous solution sprayed in the stabilizer 120. Thus, even when the exhaust gas contains a high concentration of chlorine, the exhaust gas can be efficiently treated by using a higher concentration and / or a relatively large amount of ammonia-containing aqueous solution.

[0073] For example, expressed as a percentage by mass based on oxides, alkali-free glass contains: 54%~66% SiO2, 10%~23% Al2O3, 6%~12% B2O3, and 8%~26% MgO+CaO+SrO+BaO.

[0074] To obtain a high strain point, for example, alkali-free glass contains, by mass % based on oxides: 54%~68% SiO2, 10%~25% Al2O3, 0.1%~5.5% B2O3, and 8%~26% MgO+CaO+SrO+BaO.

[0075] The Cl content in alkali-free glass is, for example, 0.1% to 0.35% by mass. [Example]

[0076] Hereinafter, embodiments of the present invention will be described. Furthermore, in the following description, Examples 1 to 5 are embodiments, and Example 11 is a comparative example.

[0077] (Example 1) The exhaust gas discharged from the melting furnace is treated using an exhaust gas treatment device. The device shown in Figure 2 above is used as the exhaust gas treatment device. The operating conditions of each component of the exhaust gas treatment device are as follows. [Melting Furnace] Glass melting temperature: 1600℃ Glass raw materials: Raw materials for manufacturing alkali-free glass (AN100 from AGC Corporation). Exhaust temperature: 1200℃ [Stabilizer] Exhaust stabilizer inlet temperature: 750℃ Neutralizing agent 1: A 10% by mass urea aqueous solution Neutralizer 1 flow rate: 5 L / hour Neutralizer 1 mole count: 505 moles / hour Neutralizing agent 2: 0.61% by mass sodium hydroxide aqueous solution Neutralizer 2 flow rate: 3300 L / hour Neutralizer 2 mole count: 503 moles / hour Total alkali addition: 1008 moles / hour Urea addition rate: 50% Exhaust stabilizer outlet temperature: 210℃ [Bag Filter] Inlet temperature of the exhaust bag filter: 210℃ Powder material: calcium hydroxide Powder supply rate: 1.5 tons / day Exhaust bag filter outlet temperature: 190℃ [Denitrification unit] Inlet temperature of exhaust gas denitrification unit: 280℃ Reducing agent: Ammonia (supply rate = 300 L / min) Exhaust gas denitrification unit outlet temperature: 280℃ [Wet Filter Unit] Inlet temperature of the wet exhaust system: 80℃ Spray liquid: water (supply rate = 3000 L / hour) Exhaust wet scrubbing unit outlet temperature: 70℃ (Example 2~Example 5) The exhaust treatment was performed using the same equipment as in Example 1. However, in Examples 2 to 5, the conditions for the neutralizing agent sprayed in the stabilizer were changed, as shown in Table 1 below.

[0078] The other operating conditions are the same as in Example 1.

[0079] (Example 11) The exhaust treatment was performed using the same equipment as in Example 1. However, in Example 11, neutralizing agent 1 (urea aqueous solution) was not sprayed into the stabilizer. That is, only neutralizing agent 2 (sodium hydroxide aqueous solution) was sprayed under the conditions specified in Table 1 below.

[0080] The other operating conditions are the same as in Example 1. [Table 1] example 1 2 3 4 5 11 Neutralizer 1 Urea concentration (%) 10 5.8 5.8 5.8 5.8 - Urea flow rate (L / hour) 5 3 3 3 5.3 - Urea addition amount (mol / hour) 505 176 176 176 310 - Neutralizer 2 NaOH concentration (%) 0.61 0.61 0.49 0.39 0.25 0.57 NaOH flow rate (L / hour) 3300 3600 3500 3500 3500 3700 NaOH addition amount (mol / hour) 503 549 429 341 219 527 Total alkali addition (mol / hour) 1008 725 604 517 529 527 Urea addition rate (%) 50 twenty four 29 34 59 0

[0081] (result) In each case, the following items were evaluated.

[0082] (The behavior of ammonia) In Examples 1 through 5, the amount of ammonia contained in the exhaust gas was measured at various locations within the exhaust gas treatment equipment. Here, "exhaust gas" refers to exhaust gas G, the first treated gas G1, the second treated gas G2, and the fourth treated gas G4.

[0083] Figure 4 shows the results of ammonia concentration measurements in the exhaust gas obtained in each example. The measurement locations were set as stabilizer inlet (hereinafter referred to as "Location A"), stabilizer outlet (hereinafter referred to as "Location B"), bag filter outlet (hereinafter referred to as "Location C"), and directly in front of the chimney (hereinafter referred to as "Location D").

[0084] As shown in Figure 4, the amount of ammonia in the exhaust gas exhibits a characteristic behavior. That is, the amount of ammonia decreases from position A to position B, then increases again at position C, and then decreases again at position D.

[0085] The movement from position A to position B corresponds to the reaction within the stabilizer. Specifically, the urea solution sprayed into the stabilizer decomposes into ammonia immediately after spraying. Therefore, at position A, the ammonia level is high. However, the generated ammonia reacts with the chlorine and sulfur components in the exhaust gas, for example, as in the aforementioned reactions (3) and (4). Therefore, at position B, the ammonia level decreases.

[0086] On the other hand, the movement from position B to position C corresponds to the reaction within the bag filter. That is, within the bag filter, for example, as in the aforementioned reaction formula (9), the ammonium salt reacts with calcium hydroxide to generate ammonia. Therefore, at position C, the amount of ammonia increases again.

[0087] Furthermore, the movement from position C to position D corresponds to a reaction within the denitrification unit. That is, as in the aforementioned reaction formulas (10) and (11), the ammonia gas regenerated at position C is consumed by the reaction within the denitrification unit. Therefore, at position D, the amount of ammonia decreases.

[0088] It can be seen that in the exhaust gas treatment process of Examples 1 to 5, ammonia gas repeatedly increases and decreases characteristically along the flow of exhaust gas.

[0089] (Effects of exhaust treatment) Figure 5 summarizes the chlorine levels measured at the stabilizer outlet (position B) for each example. In Figure 5, the horizontal axis represents the total amount of urea and sodium hydroxide added during spraying within the stabilizer, i.e., the total alkali addition (mol / h). The vertical axis represents the chlorine level (mol / h) at the stabilizer outlet (position B).

[0090] As shown in Figure 5, the more the total alkali added, the lower the chlorine content in the exhaust gas (first treated gas G1) at position B becomes. The same trend was observed when the neutralizing agent in the spray was only sodium hydroxide (Example 11). Therefore, based on these results, it can be said that urea sprayed within the stabilizer has at least the same effect on chlorine removal as sodium hydroxide.

[0091] Figure 6 summarizes the sulfur dioxide levels measured at the stabilizer outlet (position B) for each example. In Figure 6, the horizontal axis represents the total alkali addition (mol / h) within the stabilizer. The vertical axis represents the sulfur dioxide level (mol / h) at the stabilizer outlet (position B).

[0092] As shown in Figure 6, regarding the sulfur dioxide content in the exhaust gas at location B, the more the total alkali added, the lower the sulfur dioxide content tends to be. Therefore, based on this result, it can be said that the urea sprayed inside the stabilizer has at least the same effect as sodium hydroxide in removing sulfur dioxide.

[0093] Figure 7 shows the dechlorination rates obtained in the stabilizers in each example. As can be seen from Figure 7, in Examples 1 to 5 where urea was sprayed, a dechlorination rate equal to or higher than that in Example 11 where sodium hydroxide was sprayed only was obtained. Furthermore, the dechlorination rate was calculated according to the following formula (12). Dechlorination rate (%) = 1 - Cl concentration at the bag filter inlet / Cl concentration at the stabilizer inlet (12) Figure 8 shows the desulfurization rates obtained in the stabilizers for each example. As can be seen from Figure 8, in Examples 1 to 5 where urea was sprayed, a desulfurization rate equal to or higher than that in Example 11 where sodium hydroxide was sprayed only was obtained. Furthermore, the desulfurization rate was calculated according to the following formula (13). Desulfurization rate (%) = 1 - SO2 concentration at the bag filter inlet / SO2 concentration at the stabilizer inlet (13) Figure 9 shows the denitrification rates obtained in the denitrification devices in each example. Furthermore, the denitrification rate is calculated according to the following formula (14). Denitrification rate (%) = 1 - NOx concentration directly in front of the chimney / NOx concentration at the bag filter outlet (14) As shown in Figure 9, in Examples 1-5 where urea was sprayed, a higher denitrification rate was obtained than in Example 11 where only sodium hydroxide was sprayed. This is believed to be because, as mentioned earlier, ammonia gas was generated in the bag filter in Examples 1-5. That is, it is believed that in the denitrification device, in addition to the sprayed ammonia gas, the ammonia gas generated in the previous steps also contributes to the denitrification reaction, thus enabling a high denitrification rate.

[0094] The dechlorination rate in the stabilizer, the desulfurization rate in the stabilizer, and the denitrification rate in the denitrification unit are summarized in Table 2 below for each example. [Table 2] example 1 2 3 4 5 11 Dechlorination rate (%) in stabilizer 77 82 77 80 75 75 Desulfurization rate (%) in stabilizer 73 66 67 72 66 63 Denitrification rate (%) in denitrification unit 91 91 89 93 92 77

[0095] Therefore, it can be seen that in the exhaust gas treatment processes of Examples 1 to 5, the same or better effects as those of the exhaust gas treatment process of Example 11 can be obtained for any one of the dechlorination rate, desulfurization rate and denitrification rate.

[0096] The above confirms that even when using an ammonia-containing aqueous solution as a neutralizing agent sprayed in the stabilizer, exhaust gas can be properly treated.

[0097] 100: Exhaust Treatment Equipment 110: Melting Furnace 120: Stabilizer 122: Nozzle 126: First Recycling Unit 140: Bag filter 142: Ontology part 146: Second Recycling Unit 150: Powder supply device 152: Powder Supply Room 160: Denitrification device 170: Wet scrubber 174:Piping 180: Chimney G: Exhaust G1~G4: First processing gas~Fourth processing gas S1: Product of the first reaction S2: Product of the second reaction

Claims

1. An exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of glass articles, comprising the following steps: a first step, wherein exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first treated gas; a second step, wherein the first treated gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second treated gas; and a third step, wherein the second treated gas is contacted with a reducing agent for nitrogen oxides (NOx); wherein the cooling aqueous solution used in the first step contains urea or ammonia, and the temperature of the first treated gas after the first step is in the range of 200°C to 220°C.

2. An exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of glass articles, comprising the following steps: a first step, wherein the exhaust gas generated during the melting of glass raw materials is contacted with a cooling aqueous solution to generate a first treatment gas; a second step, wherein the first treatment gas is contacted with an alkali metal salt or an alkaline earth metal salt to generate a second treatment gas; and a third step, wherein the second treatment gas is contacted with nitrogen oxides (NOx) using a reducing agent; wherein the cooling aqueous solution used in the first step contains urea or ammonia, and in the first step, the urea or ammonia reacts with the chlorine component contained in the exhaust gas.

3. The exhaust treatment method as requested in item 1 or 2, wherein the concentration of urea or ammonia in the above-mentioned cooling aqueous solution is 3% to 30% by mass.

4. The exhaust treatment method as claimed in claim 1 or 2, wherein the aforementioned cooling aqueous solution further contains sodium hydroxide or magnesium hydroxide.

5. The exhaust treatment method as described in claim 4, wherein the concentration of the aforementioned sodium hydroxide or magnesium hydroxide is 2.0% by mass or less.

6. The exhaust treatment method as claimed in claim 1 or 2, wherein the molar ratio of the amount of urea added to the above-mentioned cooling aqueous solution is 20% or more relative to the total amount of alkali added.

7. The exhaust treatment method as claimed in claim 1 or 2, wherein the alkali metal salt is sodium bicarbonate or sodium carbonate.

8. The exhaust treatment method as claimed in claim 1 or 2, wherein the alkaline earth metal salt is calcium hydroxide, calcium carbonate, or a double salt of calcium carbonate and magnesium carbonate.

9. The exhaust treatment method as requested in item 1 or 2, wherein the reducing agent is ammonia, ammonia water, or an aqueous urea solution.

10. The exhaust treatment method as claimed in claim 1 or 2, wherein the reaction product generated in the second step above is melted together with the glass raw material above.

11. A method for manufacturing a glass article, comprising the following steps: melting glass raw material to form molten glass; shaping the molten glass to form shaped glass; slowly cooling the shaped glass to obtain a glass article; and treating the venting generated in the step of forming the molten glass using any one of claims 1 to 10.

12. The manufacturing method of claim 11, wherein the glass article is made of alkali-free glass.

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