Exhaust gas treatment method and glass article manufacturing method

Abstract

To provide an exhaust gas treatment method capable of significantly suppressing the bonding problem of a neutralizer to the wall surface of a stabilizer.SOLUTION: An exhaust gas treatment method treating an exhaust gas generated in the production process of a glass article includes: a first step to form a first treatment gas by bringing the exhaust gas generated at the melting of a glass raw material into contact with a cooling aqueous solution; a second step to form a second treatment gas by bringing the first treatment gas into contact with an alkali metal salt or an alkaline earth metal salt; and a third step to bring the second treatment gas into contact with a reducer for a nitrogen oxide (NOx). The cooling aqueous solution used in the first step contains urea or ammonia.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust gas treatment method and a method for manufacturing a glass article. [Background technology]

[0002] During the manufacturing process of glass products, especially during the formation of molten glass, hydrogen chloride (HCl), sulfur oxides (SO x ), and nitrogen oxides (NO x ) Such exhaust gases must be properly treated before being released into the atmosphere.

[0003] Conventionally, exhaust gas treatment equipment has been used to treat such exhaust gases. For example, Patent Document 1 describes an exhaust gas treatment equipment that includes a stabilizer, a bag filter, and a denitrification device.

[0004] The stabilizer cools the exhaust gas and removes some of the hydrogen chloride and sulfur oxides contained in the exhaust gas. The bag filter also removes hydrogen chloride and sulfur oxides contained in the exhaust gas. Furthermore, the denitrification device reduces and removes nitrogen oxides contained in the exhaust gas. Therefore, by using such exhaust gas treatment equipment, the exhaust gas can be properly treated.

[0005] In conventional exhaust gas treatment equipment, in order to remove acids from the exhaust gas, a neutralizing agent for neutralizing the acids, such as an aqueous solution of sodium hydroxide, is sprayed in a stabilizer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-184308 A Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, the amount of exhaust gas emitted from manufacturing facilities has tended to increase along with the increase in the production capacity of glass articles. This has led to a demand for further efficiency in the treatment of exhaust gas.

[0008] In order to improve the efficiency of exhaust gas treatment, it is possible to increase the amount and / or concentration of the neutralizing agent sprayed in the stabilizer.

[0009] However, the neutralizing agent, sodium hydroxide solution, has the characteristic of being relatively viscous. Therefore, when a high concentration or large amount of the neutralizing agent (sodium hydroxide solution) is sprayed inside the stabilizer, there is a high risk that sodium hydroxide will adhere to the wall surface. Furthermore, if such adhesion becomes significant, there is a possibility that the exhaust gas flow path will be blocked.

[0010] The present invention has been made in view of the above background, and aims to provide an exhaust gas treatment method capable of significantly suppressing the problem of adhesion of a neutralizing agent to the wall surface of a stabilizer, and also aims to provide a manufacturing method of a glass article using such an exhaust gas treatment method. [Means for solving the problem]

[0011] The present invention provides an exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of a glass article, the method comprising the steps of: a first step of contacting exhaust gas generated during the melting of glass raw materials with a cooling aqueous solution to generate a first treatment gas; a second step of contacting the first treatment gas with an alkali metal salt or an alkaline earth metal salt to generate a second treatment gas; and a second step of treating the second treatment gas with nitrogen oxides (NO x and a third step of contacting the aqueous cooling solution used in the first step with a reducing agent for reducing the amount of urea or ammonia contained therein. Effect of the Invention

[0012] The present invention provides an exhaust gas treatment method capable of significantly suppressing the problem of adhesion of a neutralizing agent to the wall surface of a stabilizer, and a manufacturing method of a glass article using such an exhaust gas treatment method. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a flow of an exhaust gas treatment method according to an embodiment of the present invention; [Diagram 2] 1 is a diagram showing a schematic configuration example of an exhaust gas treatment facility for carrying out an exhaust gas treatment method according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a flow of a method for manufacturing a glass article according to one embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a summary of the measurement results of the amount of ammonia in exhaust gas obtained in each example. [Diagram 5] 1 is a graph showing the amount of chlorine measured at the stabilizer outlet in each example. [Figure 6] 1 is a graph summarizing the amount of sulfur dioxide measured at the stabilizer outlet in each example. [Figure 7] 1 is a graph showing the salt rejection rates obtained with the stabilizers in each example. [Figure 8] 1 is a graph showing the desulfurization rates of the stabilizers obtained in each example. [Figure 9] 1 is a graph showing the denitration rates of the denitration devices obtained in each example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, one embodiment of the present invention will be described.

[0015] As described above, in the conventional exhaust gas treatment method, an aqueous sodium hydroxide solution is used as a neutralizing agent sprayed in the stabilizer. However, the aqueous sodium hydroxide solution has a relatively high viscosity, and when a high-concentration or large amount of the aqueous sodium hydroxide solution is sprayed, there is a problem that the risk of the sodium hydroxide adhering to the wall surface of the stabilizer increases.

[0016] In view of the above, one embodiment of the present invention is an exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of a glass article, the method comprising the steps of: a first step of contacting exhaust gas generated when a glass raw material is dissolved with a cooling aqueous solution to generate a first treatment gas; a second step of contacting the first treatment gas with an alkali metal salt or an alkaline earth metal salt to generate a second treatment gas; and a second step of treating the second treatment gas with nitrogen oxides (NO x and a third step of contacting the aqueous cooling solution used in the first step with a reducing agent for reducing the amount of urea or ammonia contained therein.

[0017] In the exhaust gas treatment method according to one embodiment of the present invention, an aqueous cooling solution containing urea or ammonia (hereinafter, these are collectively referred to as "aqueous solution containing ammonia") is used in the first step.

[0018] The urea aqueous solution and the ammonia aqueous solution have lower viscosity than the sodium hydroxide aqueous solution, and therefore, when an ammonia-containing aqueous solution is used as the neutralizing agent in the first step, the problem of the neutralizing agent adhering to the wall surface of the stabilizer can be significantly alleviated even if the ammonia-containing aqueous solution has a relatively high concentration and / or a large amount.

[0019] Therefore, the exhaust gas treatment method according to one embodiment of the present invention makes it possible to treat the exhaust gas more efficiently than in the past.

[0020] In one embodiment of the present invention, the ammonia-containing aqueous solution may be used alone or in combination with an aqueous sodium hydroxide solution. In the latter case, a mixed aqueous solution containing urea or ammonia and sodium hydroxide may be used, or the aqueous ammonia-containing aqueous solution and the aqueous sodium hydroxide solution may be used separately. In the latter case, the concentration and / or spray amount of the aqueous sodium hydroxide solution can be significantly reduced compared to the case where the aqueous sodium hydroxide solution is used alone.

[0021] (Exhaust gas treatment method according to one embodiment of the present invention) Hereinafter, an exhaust gas treatment method according to an embodiment of the present invention will be described in more detail with reference to the drawings.

[0022] FIG. 1 shows a schematic flow of an exhaust gas treatment method according to one embodiment of the present invention.

[0023] As shown in FIG. 1, an exhaust gas treatment method according to an embodiment of the present invention includes a first step (step S110) of contacting exhaust gas generated when melting a glass raw material with an aqueous cooling solution to produce a first reaction product and a first treatment gas, the aqueous cooling solution containing urea or ammonia; a second step (step S120) of contacting the first treatment gas with an alkali metal salt or an alkaline earth metal salt to produce a second reaction product and a second treatment gas; and a second step of converting the second treatment gas into nitrogen oxides (NO x and a third step (step S130) of contacting the reactant with a reducing agent for reducing the reactant.

[0024] FIG. 2 shows a schematic configuration example of an exhaust gas treatment facility (hereinafter simply referred to as "treatment facility") for carrying out the exhaust gas treatment method according to one embodiment of the present invention.

[0025] As shown in FIG. 2, the treatment facility 100 includes a melting furnace 110, a stabilizer 120, a bag filter 140, a denitration device 160, a wet device 170, and a chimney 180.

[0026] The melting furnace 110 is used to melt glass raw materials to form molten glass.

[0027] The stabilizer 120 is installed downstream of the melting furnace 110, and is provided to cool the exhaust gas G generated in the melting furnace 110. The stabilizer 120 also has one or more spray nozzles 122 capable of spraying a neutralizing agent, and a first recovery means 126 for recovering a product generated by the reaction between the exhaust gas G and the neutralizing agent (hereinafter referred to as a "first reaction product S1").

[0028] The bag filter 140 is installed downstream of the stabilizer 120. The bag filter 140 is provided to treat the treatment gas (hereinafter referred to as the "first treatment gas") G1 discharged from the stabilizer 120. The bag filter 140 also has a plurality of main bodies 142, a powder supplying device 150 that supplies powder to each of the main bodies 142, and a second recovery means 146 for recovering a product generated in the main bodies 142 (hereinafter referred to as the "second reaction product S2").

[0029] A filter cloth (not shown) that forms a flow path for the first processing gas G1 is installed in each main body 142. The filter cloth is made of a resin such as polytetrafluoroethylene. The powder supplying device 150 has a plurality of powder supplying chambers 152, and each powder supplying chamber 152 is connected to the corresponding main body 142. In the example shown in FIG. 2, each of the main body 142 and the powder supplying chamber 152 is composed of three compartments. However, the number of these is not particularly limited.

[0030] The denitration device 160 is installed downstream of the bag filter 140. The denitration device 160 is provided to treat the treated gas (hereinafter referred to as the "second treated gas") G2 discharged from the bag filter 140. The denitration device 160 also has a catalyst and an injection nozzle for a reducing agent (neither of which are shown). The catalyst may include, for example, vanadium pentoxide (V2O5).

[0031] The wet device 170 is provided downstream of the denitration device 160. The wet device 170 has a role of recovering water-soluble components contained in the treated gas (hereinafter referred to as "third treated gas") G3 discharged from the denitration device 160. The wet device 170 also has a nozzle for spraying liquid and a tank for recovering waste liquid (neither of which is shown). The liquid may be, for example, water or an aqueous solution. Furthermore, the wet device 170 may be connected to a pipe 174 for returning the waste liquid recovered in the tank to the stabilizer 120. Note that the wet device 170 may be omitted in the treatment facility 100.

[0032] The chimney 180 is provided to release the treated gas (hereinafter referred to as the "fourth treated gas") G4 discharged from the wet device 170 into the atmosphere. However, if the treatment facility 100 does not have the wet device 170, the third treated gas G3 from the denitrification device 160 is introduced into the chimney 180.

[0033] Hereinafter, each step in the exhaust gas treatment method according to one embodiment of the present invention (hereinafter referred to as the "first method") will be described with reference to FIG.

[0034] (Step S110) First, in a melting furnace 110, glass raw materials are melted to form molten glass. When the glass raw materials are melted, exhaust gas G is generated. This exhaust gas G contains various components such as chlorine components, sulfur components, and nitrogen components. The chlorine components are mainly hydrogen chloride (HCl), and the sulfur components are mainly sulfur oxides (SO x ), and the nitrogen component is mainly nitrogen oxide (NO x ) Since exhaust gas G cannot be discharged as is, it is properly treated as follows:

[0035] The exhaust gas G is supplied to the stabilizer 120. The exhaust gas G is cooled by passing through the stabilizer 120. The inlet temperature of the stabilizer 120 is in the range of 700°C to 900°C, for example, and the outlet temperature is in the range of 200°C to 220°C, for example.

[0036] As described above, the stabilizer 120 is provided with one or more spray nozzles 122, and the neutralizing agent, ie, a cooling aqueous solution, is sprayed from these spray nozzles 122. The neutralizing agent includes an "ammonia-containing aqueous solution", that is, an aqueous solution containing urea or ammonia. The "ammonia-containing aqueous solution" has a relatively low viscosity, and is unlikely to cause the above-mentioned problem, that is, the problem of the neutralizing agent adhering to the inner wall of the stabilizer 120. Therefore, a relatively high concentration ammonia-containing aqueous solution or a relatively large amount of ammonia-containing aqueous solution can be used.

[0037] In addition, the first reaction product S1 produced by the reaction of the "ammonia-containing aqueous solution" with the exhaust gas G is less likely to adhere to the inner wall of the stabilizer 120 than the sodium hydroxide aqueous solution. Specifically, the "ammonia-containing aqueous solution" reacts with the chlorine and sulfur components contained in the exhaust gas G to produce ammonium chloride and ammonium sulfate (see reaction formulas (1) to (4) described later). On the other hand, the sodium hydroxide aqueous solution reacts with the chlorine and sulfur components contained in the exhaust gas G to produce sodium chloride and sodium sulfate (see reaction formulas (5) and (6) described later). The first reaction product S1 containing ammonium chloride and ammonium sulfate has a smaller particle size and better fluidity than the first reaction product S1 containing sodium chloride and sodium sulfate, and therefore is less likely to adhere to the inner wall of the stabilizer 120.

[0038] The cooling aqueous solution preferably has a urea or ammonia concentration of 3% by mass to 30% by mass. If the urea or ammonia concentration is 3% by mass or more, hydrogen chloride (HCl) and sulfur oxides (SO x ) can be efficiently treated. If the concentration of urea or ammonia is 30% by mass or less, the viscosity of the cooling aqueous solution is low, and the problem of the neutralizing agent adhering to the inner wall of the stabilizer 120 is unlikely to occur. The concentration of urea or ammonia is more preferably 5% by mass to 25% by mass.

[0039] The cooling aqueous solution preferably further 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 even more preferably 1.0% by mass or less. If the concentration is higher than this, the viscosity of the cooling aqueous solution increases, which may cause problems with adhesion to the wall surface.

[0040] In addition, the molar ratio of the amount of urea added to the total amount of alkali added contained in the entire neutralizing agent (cooling aqueous solution) to be sprayed (hereinafter referred to as the "urea addition rate") is preferably 20% or more, and more preferably 30% or more. Here, the total amount of alkali added refers to the total number of moles of urea, ammonia, sodium hydroxide, and magnesium hydroxide added to the neutralizing agent. If the urea addition rate is 20% or more, hydrogen chloride (HCl) and sulfur oxides (SO x ) can be processed efficiently.

[0041] In addition, the molar ratio of the amount of ammonia added to the total amount of alkali added contained in the entire neutralizing agent (cooling aqueous solution) to be sprayed (hereinafter referred to as the "ammonia addition rate") is preferably 30% or more, and more preferably 50% or more. If the ammonia addition rate is 30% or more, hydrogen chloride (HCl) and sulfur oxides (SO x ) can be processed efficiently.

[0042] Note that different neutralizing agents may be sprayed from each spray nozzle 122. Alternatively, the same neutralizing agent may be sprayed from each spray nozzle 122. For example, one spray nozzle 122 may be used to spray an aqueous solution containing ammonia, and another spray nozzle 122 may be used to spray an aqueous solution of sodium hydroxide. Alternatively, a mixed aqueous solution containing urea or ammonia and sodium hydroxide may be sprayed from a single spray nozzle 122.

[0043] The sprayed neutralizing agent vaporizes in the stabilizer 120 and comes into contact with the chlorine components 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.

[0044] For example, when the neutralizing agent contains urea, hydrogen chloride and sulfur oxides are believed to be separated from exhaust gas G according to the following reactions (1) and (2), respectively. 2HCl+(NH2)2CO+H2O=2NH4Cl+CO2(1) SO3+(NH2)2CO+2H2O=(NH4)2SO4+CO2(2) Furthermore, when the neutralizing agent contains ammonia, it is believed that hydrogen chloride and sulfur oxides are separated from exhaust gas G by the following reaction equations (3) and (4), respectively. HCl+NH3=NH4Cl (3) SO3+2NH3+H2O=(NH4)2SO4(4) Furthermore, when the neutralizing agent contains sodium hydroxide, hydrogen chloride and sulfur oxides are separated from the exhaust gas G according to the following reactions (5) and (6), respectively. HCl+NaOH=NaCl+H2O (5) SO3+2NaOH=Na2SO4+H2O (6) In this manner, by passing through the stabilizer 120, a part of the chlorine components and sulfur components are removed from the exhaust gas G as the first reaction product S1, and a first treated gas G1 is discharged.

[0045] The generated first reaction product S1 is recovered by the first recovery means 126.

[0046] (Process S120) Next, the first processing gas G1 discharged from the stabilizer 120 is supplied to the main body 142 of the bag filter 140. The temperature of the main body 142 is, for example, in the range of 180° C. to 220° C. As described above, the main body 142 is connected to each powder supply chamber 152 of the powder supply device 150, and powder is supplied from these powder supply chambers 152 to the main body 142.

[0047] The powder is composed of an alkali metal salt and / or an alkaline earth metal salt. The alkali metal salt is preferably sodium hydrogen carbonate or sodium carbonate. The alkaline earth metal salt is preferably calcium hydroxide, calcium carbonate, or a double salt of calcium carbonate and magnesium carbonate. In this specification, the alkaline earth metal salt includes the hydroxide of an alkaline earth metal.

[0048] The powder supplied to the main body 142 comes into contact with the chlorine and sulfur components contained in the first process gas G1. As a result, a second reaction product S2 and a second process gas G2 are generated. For example, when the powder contains calcium hydroxide, hydrogen chloride and sulfur oxides are separated from the first process gas G1 by the following reaction formulas (7) and (8), respectively. 2HCl+Ca(OH)2=CaCl2+2H2O (7) SO3+Ca(OH)2=CaSO4+H2O (8) In this way, by passing through the bag filter 140, a part of the chlorine components and sulfur components are removed from the first treated gas G1 as the second reaction product S2, and the second treated gas G2 is discharged. The second reaction product S2 is recovered by the second recovery means 146.

[0049] Here, as shown in the above-mentioned reaction formula (1), the first processing gas G1 contains ammonium chloride (NH4Cl) generated by the reaction in step S110. This ammonium chloride reacts with the supplied powder (calcium hydroxide) in the bag filter 140 as shown in the following reaction formula (9), and can be converted into calcium chloride and ammonia. 2NH4Cl+Ca(OH)2=CaCl2+2NH3+2H2O (9) Therefore, when calcium hydroxide is used as the powder, the second process gas G2 is considered to contain ammonia generated by this reaction. This ammonia can be utilized in the subsequent step S130.

[0050] Furthermore, as is clear from reaction formula (9), when the powder supplied to the bag filter 140 is calcium hydroxide, the supplied calcium hydroxide is also consumed when ammonia is produced. It is known that usually, most of the calcium hydroxide supplied to the bag filter 140 remains unreacted. However, in the first method, for example, reaction formula (9) can significantly reduce the amount of calcium hydroxide remaining unreacted in the bag filter 140. Therefore, the powder supplied to the bag filter 140 can be used more efficiently.

[0051] The concentration of sulfur components contained in the second treated gas G2 discharged from the bag filter 140 is, for example, 100 mg / Nm3 in terms of sulfur dioxide (SO2). 3 The concentration of the chlorine component contained in the second process gas G2 is, for example, 100 mg / Nm3 in terms of hydrogen chloride (HCl). 3 The following is the result.

[0052] (Step S130) Next, the second treated gas G2 discharged from the bag filter 140 is supplied to the denitration device 160.

[0053] The second process gas G2 may be heated before being supplied to the denitration device 160. By heating the second process gas G2, the reaction efficiency in the denitration device 160 is improved. The heating temperature may be in the range of 250°C to 300°C, for example.

[0054] When the second process gas G2 is supplied to the denitration device 160, a reducing agent is injected from an injection nozzle. The reducing agent is preferably ammonia gas, ammonia water, or urea water. When the second process gas G2 comes into contact with the reducing agent (ammonia gas or ammonia water), for example, reactions shown in the following reaction formulas (10) and (11) occur. NO+NO2+2NH3=2N2+3H2O (10) SO3+2NH3+H2O=(NH4)2SO4(11) As a result, the nitrogen oxides and sulfur oxides in the second process gas G2 are removed, and the third process gas G3 is generated.

[0055] As described above, the second process gas G2 may contain ammonia (see reaction formula (9)). This ammonia may be used to react with nitrogen oxides and sulfur oxides. In this case, the amount of reducing agent supplied from the injection nozzle in the denitration device 160 can be suppressed.

[0056] The temperature of the third process gas G3 discharged from the denitration device 160 is, for example, in the range of 250° C. to 300° C. The concentration of nitrogen oxides contained in the third process gas G3 is, for example, 800 mg / Nm 3 The following is the result.

[0057] Thereafter, if necessary, the third process gas G3 discharged from the denitrification device 160 may be supplied to the wet device 170. By using the wet device 170, the sulfur components, chlorine components, and other components that remain and cannot be removed by the upstream device are removed here. Specifically, when the third process gas G3 is supplied to the wet device 170, a liquid such as water is sprayed from a nozzle. As a result, the sulfur components, chlorine components, and other components dissolve in the water, and these remaining components can be collected in a tank. The aqueous solution collected in the tank may be returned to the stabilizer 120 via a pipe 174. In this case, the amount of waste liquid to be disposed of can be reduced.

[0058] Thereafter, the fourth process gas G4 discharged from the wet-type device 170 is released into the atmosphere via a chimney 180. The fourth process gas G4 may be heated to, for example, 200° C. to 250° C. before being supplied to the chimney 180 in order to prevent condensation.

[0059] However, as described above, the wet device 170 is not an essential component and may be omitted. In this case, the third process gas G3 from the denitration device 160 is supplied to the chimney 180 as is or after being heated to prevent condensation.

[0060] As described above, the first method can properly treat the exhaust gas G through such steps. Taking the first method as an example, the exhaust gas treatment method according to one embodiment of the present invention has been described.

[0061] However, the above description is merely an example, and the exhaust gas treatment method according to one embodiment of the present invention may have other steps. For example, in step S120 of the first method, the second reaction product S2 recovered by the second recovery means 146 may be returned to the melting furnace 110 and melted together with the glass frit. In this case, the amount of waste discharged from the treatment facility 100 can be significantly reduced. In addition, each step can be modified, changed, and a new step can be added.

[0062] (Method of manufacturing a glass article according to one embodiment of the present invention) Next, a method for producing a glass article according to one embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 shows a schematic flow of the method for producing a glass article according to one embodiment of the present invention.

[0063] As shown in FIG. 3, a method for manufacturing a glass article according to one embodiment of the present invention (hereinafter simply referred to as the "manufacturing method") includes a step (S210) of melting glass raw materials to form molten glass, a step (S220) of shaping the molten glass to form shaped glass, and a step (S230) of annealing the shaped glass to obtain a glass article.

[0064] Each step will be described below.

[0065] (Step S210) First, glass raw materials are melted in the melting furnace 110 as shown in FIG. 2 described above to form molten glass.

[0066] (Process S220) The molten glass is then shaped. The shaping method is not particularly limited, and any conventional method can be used. For example, a glass ribbon may be shaped using a float method or a fusion method.

[0067] (Step S230) The formed glass is then annealed to room temperature, after which the annealed glass is cut to the desired dimensions to produce the glass article.

[0068] Here, during the production method, particularly during the formation of 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 may be treated by the above-mentioned first method. By treating the exhaust gas using the exhaust gas treatment method according to one embodiment of the present invention, the chlorine components, sulfur components, and nitrogen components contained in the exhaust gas can be properly treated.

[0069] The composition of the glass article to be produced is not particularly limited. However, for the following reasons, the production method is preferably applied to the production of alkali-free glass. Alkali-free glass refers to glass in which the total content of alkali metal oxides is 0.1 mass % or less.

[0070] When producing alkali-free glass, in step S210, glass raw materials to which a clarifier containing chlorine has been added are charged into a melting furnace 110 in order to remove bubbles contained in the molten glass. Therefore, in the process of producing alkali-free glass, exhaust gas containing a considerable amount of chlorine may be generated.

[0071] Therefore, in the manufacturing method, an aqueous solution containing ammonia, which is less likely to adhere to the wall surface, is used as the aqueous solution for cooling sprayed in the stabilizer 120. Therefore, even if the exhaust gas contains a high concentration of chlorine components, the exhaust gas can be efficiently treated by using an aqueous solution containing ammonia with a relatively high concentration and / or a large amount.

[0072] The alkali-free glass contains, for example, in mass % on an oxide basis, SiO2: 54% to 66%, Al2O3: 10% to 23%, B2O3: 6% to 12%, and MgO+CaO+SrO+BaO: 8% to 26%.

[0073] In order to have a high strain point, the non-alkali glass contains, for example, in mass % on an oxide basis, 54% to 68% SiO2, 10% to 25% Al2O3, 0.1% to 5.5% B2O3, and 8% to 26% MgO+CaO+SrO+BaO.

[0074] The Cl content of the alkali-free glass is, for example, 0.1% by mass to 0.35% by mass. EXAMPLES

[0075] Examples of the present invention will now be described below, in which Examples 1 to 5 are examples and Example 11 is a comparative example.

[0076] (Example 1) The exhaust gas discharged from the melting furnace was treated using an exhaust gas treatment system. The equipment used was the one shown in Figure 2. The operating conditions for each device in the exhaust gas treatment system are as follows: [Melting furnace] Glass melting temperature: 1600℃ Glass raw material; raw material for manufacturing alkali-free glass (AGC Corporation's AN100) Exhaust gas temperature: 1200℃ [stabilizer] Exhaust gas stabilizer inlet temperature: 750℃ Neutralizer 1: 10% urea aqueous solution Neutralizer 1 flow rate: 5L / hour Moles of neutralizer 1: 505 mol / hour Neutralizer 2: 0.61% by weight aqueous sodium hydroxide solution Neutralizer 2 flow rate: 3300L / hour Moles of neutralizer 2: 503 mol / hour Total alkali addition: 1008 mol / hour Urea addition rate: 50% Exhaust gas stabilizer outlet temperature: 210℃ [Bag filter] Exhaust gas bag filter inlet temperature: 210℃ Powdered materials; calcium hydroxide Powder supply rate: 1.5 tons / day Exhaust gas bag filter outlet temperature: 190℃ [Denitration equipment] Exhaust gas denitrification device inlet temperature: 280℃ Reducing agent: Ammonia gas (supply rate = 300 L / min) Exhaust gas denitrification device outlet temperature: 280℃ [Wet equipment] Exhaust gas temperature at the inlet to the wet device: 80℃ Spray liquid; water (supply amount = 3000L / hour) Exhaust gas outlet temperature of wet device: 70℃ (Examples 2 to 5) Exhaust gas was treated 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.

[0077] Other operating conditions were the same as in Example 1.

[0078] (Example 11) Exhaust gas was treated using the same equipment as in Example 1. However, in this Example 11, neutralizer 1 (urea aqueous solution) was not sprayed in the stabilizer. That is, only neutralizer 2 (sodium hydroxide aqueous solution) was sprayed under the conditions in Table 1 below.

[0079] Other operating conditions were the same as in Example 1. [Table 1]

[0080] (result) In each case, the following items were evaluated:

[0081] (Behavior of ammonia gas) The amount of ammonia contained in the exhaust gas was measured at each position of the exhaust gas treatment equipment in each of Examples 1 to 5. The exhaust gas here refers to the exhaust gas G, the first treatment gas G1, the second treatment gas G2, and the fourth treatment gas G4.

[0082] The measurement results of the amount of ammonia in the exhaust gas obtained in each example are shown in Figure 4. The measurement points were the stabilizer inlet (hereinafter referred to as "position A"), the stabilizer outlet (hereinafter referred to as "position B"), the bag filter outlet (hereinafter referred to as "position C"), and just before the chimney (hereinafter referred to as "position D").

[0083] As shown in Figure 4, the amount of ammonia in the exhaust gas exhibited a characteristic behavior. That is, the amount of ammonia decreased from position A to position B, then increased again at position C, and then decreased again at position D.

[0084] Among these, the behavior from position A to position B corresponds to the reaction in the stabilizer. That is, the urea solution sprayed in the stabilizer immediately decomposes into ammonia gas. For this reason, the amount of ammonia increases at position A. However, the generated ammonia gas reacts with the chlorine and sulfur components contained in the exhaust gas and is consumed, for example, as shown in the above-mentioned reactions (3) and (4). Therefore, the amount of ammonia decreases at position B.

[0085] On the other hand, the behavior from position B to position C corresponds to the reaction in the bag filter. That is, in the bag filter, for example, ammonium salt reacts with calcium hydroxide to generate ammonia gas, as shown in the above reaction formula (9). Therefore, the amount of ammonium increases again at position C.

[0086] Furthermore, the behavior from position C to position D corresponds to the reaction in the denitration device. That is, the ammonia gas regenerated at position C is consumed in the reaction in the denitration device as shown in the above-mentioned reaction equations (10) and (11). Therefore, the amount of ammonia decreases at position D.

[0087] As described above, in the exhaust gas treatment processes in Examples 1 to 5, it was found that ammonia gas repeatedly increased and decreased in a characteristic manner along the flow of the exhaust gas.

[0088] (Effects of exhaust gas treatment) Figure 5 shows the amount of chlorine measured at the stabilizer outlet (position B) in each example. In Figure 5, the horizontal axis represents the sum of the amount of urea and sodium hydroxide sprayed in the stabilizer, i.e., the total amount of alkali added (mol / hour). The vertical axis represents the amount of chlorine (mol / hour) at the stabilizer outlet (position B).

[0089] From Fig. 5, it can be seen that the amount of chlorine contained in the exhaust gas (first treated gas G1) at position B tends to decrease as the total amount of alkali added increases. A similar tendency is observed when the only neutralizing agent sprayed is sodium hydroxide (Example 11). Therefore, from these results, it can be said that urea sprayed in the stabilizer has at least the same effect as sodium hydroxide in removing chlorine.

[0090] Figure 6 shows the amount of sulfur dioxide measured at the stabilizer outlet (position B) for each example. In Figure 6, the horizontal axis represents the total amount of alkali added (mol / hour) in the stabilizer, and the vertical axis represents the amount of sulfur dioxide (mol / hour) at the stabilizer outlet (position B).

[0091] From Fig. 6, it can be seen that the amount of sulfur dioxide contained in the exhaust gas at position B also tends to decrease as the total amount of alkali added increases. Therefore, from these results, it can be said that the urea sprayed in the stabilizer has at least the same effect as sodium hydroxide in removing sulfur dioxide.

[0092] Figure 7 shows the salt rejection rate obtained with the stabilizer in each example. It can be seen from Figure 7 that in Examples 1 to 5, in which urea was sprayed, a salt rejection rate equal to or higher than that in Example 11, in which only sodium hydroxide was sprayed. The salt rejection rate was calculated from the following formula (12). Desalination rate (%)=1- Cl concentration at bag filter inlet / Cl concentration at stabilizer inlet (12) Fig. 8 shows the desulfurization rate of the stabilizer obtained in each example. It can be seen from Fig. 8 that in Examples 1 to 5, in which urea was sprayed, a desulfurization rate equal to or higher than that in Example 11, in which only sodium hydroxide was sprayed. The desulfurization rate was calculated from the following formula (13). Desulfurization rate (%)=1- SO2 concentration at the bag filter inlet / SO2 concentration at the stabilizer inlet (13) The denitration efficiency obtained in each example is shown in Figure 9. The denitration efficiency was calculated from the following formula (14). Denitrification rate (%)=1- NO before the chimney x Concentration / NO at bag filter outlet x Concentration (14) 9 shows that in Examples 1 to 5 in which urea was sprayed, a high denitration rate was obtained that exceeded the denitration rate in Example 11 in which only sodium hydroxide was sprayed. This is believed to be because, as described above, ammonia gas is generated in the bag filter in Examples 1 to 5. That is, in the denitration device, in addition to the ammonia gas sprayed, the ammonia gas generated in the previous process also contributes to the denitration reaction, which is believed to be why a high denitration rate was obtained.

[0093] Table 2 below shows the salt removal rate in the stabilizer, the sulfur removal rate in the stabilizer, and the NOx removal rate in the denitrification device obtained in each example. [Table 2]

[0094] As described above, it was found that the exhaust gas treatment processes in Examples 1 to 5 had effects equal to or greater than those of the exhaust gas treatment process in Example 11 in terms of salt removal rate, sulfur removal rate, and NOx removal rate.

[0095] From the above, it was confirmed that exhaust gas can be properly treated even if an aqueous ammonia-containing solution is used as the neutralizing agent sprayed in the stabilizer. [Explanation of symbols]

[0096] 100 Exhaust gas treatment equipment 110 Melting furnace 120 Stabilizer 122 Spray nozzle 126 First Recovery Method 140 Bag Filter 142 Main body 146 Secondary Recovery Method 150 Powder feeding device 152 Powder supply room 160 Denitration equipment 170 Wet equipment 174 Piping 180 Chimney G. Exhaust gas G1 to G4: First processing gas to fourth processing gas S1 First reaction product S2 Second reaction product

Claims

1. An exhaust gas treatment method for treating exhaust gas generated during the manufacturing process of a glass article, comprising: A first step of contacting exhaust gas generated when melting a glass raw material with an aqueous cooling solution to generate a first process gas; a second step of contacting the first process gas with an alkali metal salt or an alkaline earth metal salt to produce a second process gas; The second process gas is nitrogen oxide (NO ｘ a third step of contacting the resulting mixture with a reducing agent for having The cooling aqueous solution used in the first step contains urea or ammonia, The exhaust gas treatment method, wherein the temperature of the first treatment gas after the first step is in the range of 200°C to 220°C.

2. A method for treating exhaust gas generated during the manufacturing process of a glass article, comprising: A first step of contacting exhaust gas generated when melting a glass raw material with an aqueous cooling solution to generate a first process gas; a second step of contacting the first process gas with an alkali metal salt or an alkaline earth metal salt to produce a second process gas; a third step of contacting the second treat gas with a reducing agent for nitrogen oxides (NOx); having The cooling aqueous solution used in the first step contains urea or ammonia, In the first step, the urea or ammonia reacts with a chlorine component contained in the exhaust gas.

3. 3. The exhaust gas treatment method according to claim 1, wherein the cooling aqueous solution has a urea or ammonia concentration of 3% by mass to 30% by mass.

4. The exhaust gas treatment method according to any one of claims 1 to 3, wherein the cooling aqueous solution further contains sodium hydroxide or magnesium hydroxide.

5. The exhaust gas treatment method according to claim 4 , wherein the concentration of the sodium hydroxide or magnesium hydroxide is 2.0 mass % or less.

6. 6. The exhaust gas treatment method according to claim 1, wherein a molar ratio of an amount of urea added to a total amount of alkali added contained in the aqueous cooling solution is 20% or more.

7. The exhaust gas treatment method according to any one of claims 1 to 6, wherein the alkali metal salt is sodium hydrogen carbonate or sodium carbonate.

8. The exhaust gas treatment method according to any one of claims 1 to 7, wherein the alkaline earth metal salt is calcium hydroxide, calcium carbonate, or a double salt of calcium carbonate and magnesium carbonate.

9. The exhaust gas treatment method according to any one of claims 1 to 8, wherein the reducing agent is ammonia gas, ammonia water or urea water.

10. The exhaust gas treatment method according to any one of claims 1 to 9, wherein the reaction product produced in the second step is melted together with the glass raw material.

11. A method for manufacturing a glass article, comprising the steps of: Melting glass raw materials to form molten glass; shaping the molten glass to form a shaped glass; A step of slowly cooling the formed glass to obtain a glass article; having A manufacturing method, wherein exhaust gas generated in the step of forming the molten glass is treated by using the exhaust gas treatment method according to any one of claims 1 to 10.

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

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