Molten glass manufacturing apparatus, glass article manufacturing apparatus, and method for manufacturing molten glass

Abstract

A method, for producing a mixed feedstock, according to the present invention involves: a glass feedstock and an aqueous solution of sodium hydroxide being prepared, carbon dioxide gas being absorbed into the aqueous solution to obtain sodium bicarbonate, and the sodium bicarbonate and the glass feedstock being mixed to obtain a mixed feedstock that will be introduced into a melting furnace.

Description

[Technical field]

[0001] The present disclosure relates to a method for producing a raw material mixture, a method for producing molten glass, a method for producing a glass article, an apparatus for producing molten glass, and an apparatus for producing a glass article. [Background technology]

[0002] Carbon dioxide gas is generated during the manufacturing process of molten glass. Carbon dioxide gas is a greenhouse gas and is considered to be one of the causes of global warming. Therefore, there is a demand to reduce the amount of carbon dioxide gas generated.

[0003] The sources of carbon dioxide gas in the manufacturing process of molten glass are mainly classified into fuels such as natural gas and carbonates, which are raw materials for glass. Carbon dioxide gas is generated by the combustion of fuels. Carbon dioxide gas is also generated by the thermal decomposition of carbonates.

[0004] Carbonates are widely used as glass raw materials because they are stable at room temperature in the air and inexpensive. For example, sodium carbonate (Na2CO3) is generally used as a sodium source for glass.

[0005] In Patent Documents 1 and 2, sodium hydroxide (NaOH) is used as the sodium source for glass. NaOH does not contain carbon, so it does not generate carbon dioxide gas. NaOH is usually distributed in the form of an aqueous solution.

[0006] However, NaOH has a high vapor pressure and is highly corrosive to the bricks of a melting furnace (see, for example, Non-Patent Document 1). Therefore, as described above, Na2CO3 is generally used as the sodium source for glass.

[0007] In addition to Na2CO3 and NaOH, sodium bicarbonate (NaHCO3) also exists as a sodium compound. NaHCO3 is used, for example, in hemodialysis.

[0008] Patent Documents 3 and 4 describe methods for producing NaHCO3. Specifically, they describe a method in which an aqueous solution containing sodium ions is reacted with carbon dioxide gas to precipitate NaHCO3.

[0009] NaHCO3 has twice the molar ratio of carbon atoms to sodium atoms as Na2CO3, and therefore generates twice as much carbon dioxide gas as NaHCO3 does when thermally decomposed. Therefore, NaHCO3 has not been used as a sodium source for glass in the past.

[0010] Non-Patent Document 2 discloses a technology related to carbon dioxide capture and storage (CCS). This technology involves absorbing carbon dioxide gas into an aqueous solution of potassium carbonate (K2CO3), generating potassium bicarbonate (KHCO3), heating the KHCO3, and extracting the carbon dioxide gas.

[0011] The technology described in Non-Patent Document 2 is a method for separating carbon dioxide gas from gases other than carbon dioxide gas, and is not a method for reducing the amount of carbon dioxide gas generated. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] US Patent No. 4211568 [Patent Document 2] Japanese Patent Publication No. 49-31717 [Patent Document 3] International Publication No. 2006 / 021993 [Patent Document 4] Japanese Patent No. 4724996 [Non-patent literature]

[0013] [Non-Patent Document 1] RGC Beerkens and OS “Verheijen, Reactions of alkali vapours with silica based refractory in glass furnaces, thermodynamics and mass transfer” Physics and Chemistry of Glasses, Volume 46, Number 6, December 2005, pp-583-594 [Non-Patent Document 2] C. Andeson et al., Developments in the CO2CRC UNO MK 3 Process: A Multi-component Solvent Process for Large Scale CO2 Capture, Energy Procedia, 37, 2013, 225-232 Summary of the Invention [Problem to be solved by the invention]

[0014] One aspect of the present disclosure provides a technique capable of reducing the amount of carbon dioxide gas generated in a process for producing molten glass. [Means for solving the problem]

[0015] The present invention is a method for producing a mixed raw material, comprising the steps of preparing an aqueous solution of a glass raw material and sodium hydroxide, allowing the aqueous solution to absorb carbon dioxide gas, precipitating sodium hydrogen carbonate in the aqueous solution, mixing the sodium hydrogen carbonate and the glass raw material, and obtaining a mixed raw material to be charged into a melting furnace.

[0016] In the manufacturing method according to one aspect of the present invention, the mixed raw material may further be heated before the mixed raw material is charged into the melting furnace to convert the sodium hydrogen carbonate into sodium carbonate, thereby obtaining the carbon dioxide gas.

[0017] In the manufacturing method according to one aspect of the present invention, the mixed raw material may be heated by utilizing heat of an exhaust gas from the melting furnace.

[0018] In the production method according to one aspect of the present invention, the mixed raw material is preferably heated at a temperature of 100°C to 900°C.

[0019] In the manufacturing method according to one aspect of the present invention, the carbon dioxide gas may further be obtained from exhaust gas from the melting furnace.

[0020] In the manufacturing method according to one aspect of the present invention, the mixed raw material may further be granulated to obtain briquettes before the mixed raw material is charged into the melting furnace, and the briquettes may be used as the mixed raw material.

[0021] The present invention provides a method for producing molten glass, comprising charging the mixed raw material obtained by the above-mentioned production method into the melting furnace and melting the raw material inside the melting furnace to obtain molten glass.

[0022] In the manufacturing method according to one aspect of the present invention, the mixed raw material obtained by the manufacturing method is preferably charged into the melting furnace without being cooled to room temperature, and melted inside the melting furnace to obtain molten glass.

[0023] The present invention relates to a method for producing a glass article, which comprises forming the molten glass obtained by the above-mentioned production method, and slowly cooling the molten glass to obtain a glass article.

[0024] The present invention is an apparatus for producing molten glass, comprising: a raw material tank for accommodating glass raw materials; an aqueous solution tank for storing an aqueous solution of sodium hydroxide; an absorption tank for causing the aqueous solution transferred from the aqueous solution tank to absorb carbon dioxide gas and precipitate sodium bicarbonate; a mixer for mixing the glass raw materials transferred from the raw material tank and the sodium bicarbonate transferred from the absorption tank to obtain a mixed raw material; a storage tank for storing the mixed raw material transferred from the mixer; and a melting furnace for melting the mixed raw material transferred from the storage tank to obtain molten glass.

[0025] In one embodiment of the manufacturing apparatus of the present invention, the absorption tank may include a first tank in which carbon dioxide gas is absorbed into the aqueous solution to obtain sodium carbonate, a second tank in which carbon dioxide gas is further absorbed into the aqueous solution transferred from the first tank to obtain the sodium bicarbonate in the aqueous solution, and a first gas pipe in which carbon dioxide gas remaining in the second tank is transferred to the first tank.

[0026] The manufacturing apparatus of one embodiment of the present invention may further include a heat supplier that supplies heat to the storage tank, converts the sodium bicarbonate into sodium carbonate inside the storage tank, and obtains carbon dioxide gas to be absorbed in the absorption tank.

[0027] In the manufacturing apparatus according to one aspect of the present invention, the heat supplier may include a heat supply pipe that transfers exhaust gas combusted in the melting furnace together with heat of the exhaust gas from the melting furnace to the storage tank.

[0028] In the manufacturing apparatus according to one aspect of the present invention, the heat supplier may include a hot air generator that generates hot air separately from the melting furnace and blows the hot air into the storage tank.

[0029] The production apparatus according to one aspect of the present invention may further include a first gas pipe for transferring carbon dioxide gas in the storage tank from the storage tank to the absorption tank.

[0030] The manufacturing apparatus according to one aspect of the present invention may further include a second gas pipe for transferring carbon dioxide gas from the melting furnace to the absorption tank.

[0031] The manufacturing apparatus according to one aspect of the present invention may further include a molding machine between the storage tank and the mixer, which granulates the mixed raw material to obtain briquettes.

[0032] The present invention is an apparatus for manufacturing a glass article, comprising: an apparatus for manufacturing molten glass; a forming apparatus for forming the molten glass obtained in the melting furnace; an annealing apparatus for annealing the formed glass; and a processing apparatus for processing the annealed glass into a glass article. Effect of the Invention

[0033] According to one aspect of the present disclosure, the amount of carbon dioxide gas generated in a process for producing molten glass can be reduced. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a diagram showing an apparatus for manufacturing a glass article according to one embodiment. [Diagram 2] FIG. 2 is a flowchart showing a method for manufacturing a glass article according to one embodiment. [Diagram 3] FIG. 3 is a diagram showing an apparatus for producing molten glass according to one embodiment. [Figure 4] FIG. 4 is an elevational cross-sectional view showing an example of the melting furnace of FIG. [Figure 5A] FIG. 5A is a diagram showing an example of the heat balance of the melting furnace of FIG. 4 in the absence of the heat supply pipe of FIG. [Figure 5B] FIG. 5B is a diagram showing an example of the heat balance of the melting furnace of FIG. 4 when the heat supply pipe of FIG. 3 is present. [Figure 6] FIG. 6 is a diagram showing an example of the relationship between the decarbonation rate of the mixed raw material and the temperature. [Figure 7] FIG. 7 is a diagram showing the heat balance of the melting furnace according to the first modified example. [Figure 8] FIG. 8 is a diagram showing a molten glass producing apparatus according to a second modified example. [Figure 9] FIG. 9 is a diagram showing an apparatus for producing molten glass according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted.

[0036] (Glass article manufacturing equipment) As shown in FIG. 1, a glass article manufacturing apparatus 1 includes a molten glass manufacturing apparatus 2, a forming apparatus 3, an annealing apparatus 4, and a processing apparatus 5.

[0037] The molten glass production apparatus 2 melts the mixed raw materials to produce molten glass. The mixed raw materials include a plurality of types of glass raw materials. The glass raw materials are determined according to the composition of the glass.

[0038] When the glass is soda-lime glass, the composition of the glass, in mole percent on an oxide basis, is such that the SiO2 content is 50% or more and 75% or less, the Al2O3 content is 0% or more and 20% or less, the total content of Li2O, Na2O, and K2O is 5% or more and 25% or less, and the total content of MgO, CaO, SrO, and BaO is 0% or more and 20% or less.

[0039] When the glass is soda-lime glass, the mixed raw materials include, for example, silica sand, dolomite (MgCO3CaCO3), limestone (CaCO3), sodium bicarbonate (NaHCO3), boric acid, and a fining agent. The fining agent is sulfur trioxide, chloride, or fluoride. The mixed raw materials will be described in detail later.

[0040] In the molten glass manufacturing apparatus 2, the mixed raw materials are charged into a melting furnace, and the mixed raw materials are melted inside the melting furnace to obtain molten glass. The mixed raw materials may or may not be granulated before being charged into the melting furnace.

[0041] The manufacturing apparatus 2 may feed the mixed raw material and the glass cullet into the melting furnace. The glass cullet may be mixed with the mixed raw material before being fed into the melting furnace, or may be fed into the melting furnace separately from the mixed raw material. The manufacturing apparatus 2 will be described in detail later.

[0042] The forming apparatus 3 forms the molten glass obtained in the manufacturing apparatus 2 into glass of a desired shape. For example, a float method, a fusion method, a roll-out method, or the like is used as a forming method for obtaining a plate-shaped glass.

[0043] The annealing device 4 anneals the glass formed by the forming device 3. The annealing device 4 has, for example, an annealing furnace and transport rollers that transport the glass in a desired direction inside the annealing furnace. The transport rollers are arranged, for example, at intervals in the horizontal direction. The glass is annealed while being transported from the entrance to the exit of the annealing furnace. By annealing the glass, glass with little residual distortion can be obtained.

[0044] The processing device 5 processes the glass annealed in the annealing device 4 into a glass article. The processing device 5 may be, for example, one or more selected from a cutting device, a grinding device, a polishing device, and a coating device. The cutting device cuts out a glass article from the glass annealed in the annealing device 4. The cutting device, for example, forms a scribe line in the glass annealed in the annealing device 4 and breaks the glass along the scribe line.

[0045] The glass article manufacturing apparatus 1 may further include a fining device. The fining device removes bubbles contained in the molten glass obtained in the molten glass manufacturing apparatus 2 before the molten glass is shaped by the shaping apparatus 3.

[0046] (Method of manufacturing glass article) As shown in Fig. 2, the method for manufacturing a glass article includes production of molten glass (S1), shaping (S2), annealing (S3), and processing (S4). A molten glass manufacturing apparatus 2 performs production of molten glass (S1), a shaping apparatus 3 performs shaping (S2), an annealing apparatus 4 performs annealing (S3), and a processing apparatus 5 performs processing (S4). The method for manufacturing a glass article may further include fining. Fining is performed after production of molten glass (S1) and before shaping (S2).

[0047] (Molten glass manufacturing equipment) As shown in FIG. 3, the molten glass manufacturing apparatus 2 includes a raw material tank 61, an aqueous solution tank 62, an absorption tank 63, a dehydration tank 64, a weighing machine 65, a mixer 66, a molding machine 67, a storage tank 68, a charger 69, and a melting furnace 70.

[0048] The raw material tank 61 contains glass raw materials other than the aqueous solution stored in the aqueous solution tank 62. The raw material tank 61 contains powdered glass raw materials. The raw material tank 61 contains, for example, a silicon source, an alkaline earth metal source, and the like.

[0049] As the powdered silicon source, silica or feldspar is prepared. The silica may be any of silica sand, quartz, cristobalite, and amorphous silica. Two or more kinds of silicon sources may be prepared.

[0050] In this embodiment, carbonates are prepared as a powdered alkaline earth metal source. The alkaline earth metals refer to Mg, Ca, Ba, and Sr. As the carbonates, limestone (CaCO3) or dolomite (MgCO3·CaCO3), which are inexpensive raw materials, are preferable. Two or more types of carbonates may be prepared.

[0051] In this embodiment, a carbonate is prepared as the powdered alkaline earth metal source, but an oxide or hydroxide may be prepared instead. If an oxide or hydroxide is prepared, carbon dioxide gas is not generated during heating. Since an oxide is obtained by heating a carbonate, it is expensive, but since it does not contain carbon, the amount of carbon dioxide gas generated can be suppressed. The same applies to a hydroxide.

[0052] The raw material tank 61 may further contain an aluminum source in addition to the silicon source and the alkaline earth metal source. As the aluminum source, for example, aluminum oxide, aluminum hydroxide, feldspar, or the like is prepared. Two or more types of aluminum sources may be prepared.

[0053] Furthermore, the raw material tank 61 may further contain a boron source such as boric acid, a zirconium source such as zirconia oxide, or a clarifier, in addition to the silicon source and the alkaline earth metal source.

[0054] A plurality of types of powdered glass raw materials are prepared so as to obtain a glass having a desired composition. The plurality of types of glass raw materials may be separately accommodated in a plurality of raw material tanks 61, or may be collectively accommodated in one raw material tank 61.

[0055] The aqueous solution tank 62 stores an aqueous solution of sodium hydroxide (NaOH). An aqueous NaOH solution with a NaOH concentration of 48% by mass is usually distributed. An aqueous solution with a NaOH concentration of 48% by mass has a freezing point of 10°C and a boiling point of 138°C.

[0056] The sodium source, NaOH, does not contain carbon and is therefore not a source of carbon dioxide gas. However, NaOH has a high vapor pressure and is highly corrosive to the bricks of the melting furnace 70. Therefore, before being fed into the melting furnace 70, NaOH is converted to NaHCO3 in the absorption tank 63.

[0057] In the absorption tank 63, carbon dioxide gas is absorbed into the aqueous solution transferred from the aqueous solution tank 62, causing NaHCO3 to precipitate, and obtaining a slurry containing NaHCO3. Carbon dioxide gas at a temperature lower than the boiling point of the aqueous solution is supplied to the absorption tank 63 so that the aqueous solution in the absorption tank 63 does not boil.

[0058] First, when carbon dioxide gas is absorbed into an aqueous solution, NaOH reacts with CO2, causing the reaction shown in formula (1) below to produce Na2CO3. 2NaOH+CO2→Na2CO3+H2O···(1) Since the solubility of Na2CO3 is high, Na2CO3 dissolves in water and hardly precipitates. The solutes in the aqueous solution change from only NaOH to both NaOH and Na2CO3.

[0059] Subsequently, when more carbon dioxide gas is absorbed into the aqueous solution, Na2CO3, CO2, and water react with each other, causing the reaction of the following formula (2) to produce NaHCO3. Na2CO3+CO2+H2O→2NaHCO3···(2) Since the solubility of NaHCO3 is lower than that of Na2CO3, NaHCO3 will precipitate preferentially.

[0060] When heated, NaHCO3 decomposes into Na2CO3, CO2, and H2O, making it less corrosive to the bricks of the smelting furnace 70 than the conventional sodium source, Na2CO3.

[0061] When NaHCO3 is heated, the reaction shown in equation (3) below occurs, producing Na2CO3, CO2, and H2O. 2NaHCO3→Na2CO3+CO2+H2O···(3) The reaction of the above formula (3) is the reverse reaction of the reaction of the above formula (2).

[0062] Furthermore, when Na2CO3 is heated together with glass raw materials, for example, a reaction represented by the following formula (4) occurs, producing an alkali silicate and CO2. Na2CO3+SiO2→Na2O·SiO2+CO2···(4).

[0063] As shown in the above formulas (3) and (4), carbon dioxide gas is generated in the process of obtaining alkali silicate from NaHCO3. However, the amount of carbon dioxide gas generated is equal to the amount of carbon dioxide gas absorbed by the aqueous solution in the absorption tank 63. Therefore, the amount of carbon dioxide gas generated from the sodium source is zero in the entire process of producing molten glass.

[0064] As described above, according to the present embodiment, since NaOH is used as the sodium source, the amount of carbon dioxide gas generated in the manufacturing process of molten glass can be reduced. Since NaOH does not contain carbon, it does not become a source of carbon dioxide gas generation.

[0065] For example, when the Na2O content of glass is 14 mass% and the ratio of mixed raw materials to glass cullet is 3:1, it is estimated that the amount of carbon dioxide generated per ton of glass can be reduced by about 0.075 tons if NaOH is used instead of Na2CO3 as the sodium source.

[0066] Furthermore, according to this embodiment, NaOH is converted to NaHCO3 in the absorption tank 63 before being charged into the melting furnace 70, which can prevent erosion of the bricks of the melting furnace 70. Therefore, the frequency of maintenance of the melting furnace 70 can be reduced.

[0067] In this embodiment, the entire sodium source is an aqueous NaOH solution, but a part of the sodium source may be powdered sodium carbonate (Na2CO3). The powdered Na2CO3 is stored in the raw material tank 61. As long as at least a part of the sodium source is an aqueous NaOH solution, the amount of carbon dioxide gas generated from the sodium source can be reduced.

[0068] 3, the absorption tank 63 includes, for example, a first tank 631, a second tank 632, and an internal pipe 633. In the first tank 631, carbon dioxide gas is absorbed in an aqueous NaOH solution to obtain Na2CO3. In the first tank 631, a mixed aqueous solution of NaOH and Na2CO3 is obtained.

[0069] In the second tank 632, the mixed aqueous solution of NaOH and Na2CO3 transferred from the first tank 631 further absorbs carbon dioxide gas, and NaHCO3 is precipitated. In the second tank 632, a slurry containing NaHCO3 is obtained. The slurry contains Na2CO3 and NaHCO3 as components dissolved in water.

[0070] The reaction of formula (1) mainly occurs in the first tank 631, and the reaction of formula (2) mainly occurs in the second tank 632. The reaction of formula (2) occurs after the reaction of formula (1), and therefore requires a higher carbon dioxide concentration than the reaction of formula (1).

[0071] Therefore, the internal piping 633 transfers the carbon dioxide gas remaining in the second tank 632 to the first tank 631. The carbon dioxide gas concentration of the gas supplied to the first tank 631 is lower than the carbon dioxide gas concentration of the gas supplied to the second tank 632. In other words, the carbon dioxide gas concentration of the gas supplied to the second tank 632 is higher than the carbon dioxide gas concentration of the gas supplied to the first tank 631. According to the present embodiment, gases having carbon dioxide gas concentrations according to the respective requirements are supplied to the first tank 631 and the second tank 632, so that the carbon dioxide gas can be used efficiently inside the molten glass manufacturing apparatus 2.

[0072] In this embodiment, the carbon dioxide concentration of the gas supplied to the second tank 632 is higher than the carbon dioxide concentration of the gas supplied to the first tank 631, but it may be the same or lower. It is sufficient that the reaction of formula (1) mainly occurs in the first tank 631 and the reaction of formula (2) mainly occurs in the second tank 632.

[0073] In addition, as long as the reaction of formula (1) mainly occurs in the first tank 631, the reaction of formula (2) may also occur. In addition, the absorption tank 63 includes the first tank 631 and the second tank 632 in this embodiment, but may include one tank that serves as both the first tank 631 and the second tank 632. Since precipitation occurs in the second tank 632, a lower temperature is rather preferable.

[0074] The dehydration tank 64 dehydrates the slurry transferred from the absorption tank 63. The slurry contains precipitated powdered NaHCO3 and a liquid that is a dispersion medium for NaHCO3. The liquid contains unprecipitated Na2CO3 and NaHCO3.

[0075] The dehydration tank 64 separates the liquid from the slurry. The separation method is, for example, a centrifugation method or a filtration separation method. The liquid separated from the slurry contains unprecipitated Na2CO3 and NaHCO3, and is returned to the absorption tank 63 via the sodium recovery pipe 71. Compared to the case where the liquid is discarded, the amount of NaOH aqueous solution used as the sodium source can be reduced.

[0076] The sodium recovery pipe 71 may return the liquid separated from the slurry in the dehydration tank 64 to the first tank 631, but in this embodiment, it returns it to the second tank 632. The liquid separated from the slurry is saturated with NaHCO3. Since the liquid with a high NaHCO3 concentration is returned to the second tank 632, the reaction of formula (2) proceeds efficiently in the second tank 632.

[0077] A muddy material containing precipitated NaHCO3 and a small amount of liquid remains in the dehydration tank 64. The proportion of NaHCO3 in the muddy material is, for example, 85% by mass to 95% by mass, and the proportion of liquid in the muddy material is, for example, 5% by mass to 15% by mass.

[0078] The muddy material obtained in the dehydration tank 64 may be transferred to the weighing machine 65 via a dryer that removes liquid from the muddy material, but in this embodiment, it is transferred to the weighing machine 65 without passing through a dryer. The precipitated NaHCO3 is sent to the weighing machine 65 in a mixed state with the liquid.

[0079] The weighing machine 65 weighs the glass raw material transferred from the raw material tank 61 and NaHCO3 transferred from the dehydration tank 64 at a predetermined blending ratio. The blending ratio is determined in advance so as to obtain glass of a desired composition.

[0080] When the weighing machine 65 weighs the muddy material, the blending ratio is determined in consideration of the liquid content in the muddy material. Furthermore, the blending ratio may be determined in consideration of the Na content in the liquid.

[0081] A storage tank for storing the sludge may be provided between the dewatering tank 64 and the weighing machine 65.

[0082] The mixer 66 mixes the glass raw material transferred from the raw material tank 61 via the weigher 65 with NaHCO3 transferred from the absorption tank 63 via the weigher 65 to obtain a mixed raw material. During mixing, water or the like is added to prevent scattering of dust.

[0083] According to this embodiment, the muddy material obtained in the dehydration tank 64 is transferred to the mixer 66 without passing through a dryer. Therefore, the liquid of the muddy material can prevent dust from scattering. Therefore, it is not necessary to spray water or the like in the dehydration tank 64, or the amount of water sprayed can be reduced.

[0084] The molding machine 67 granulates the mixed raw material obtained by the mixer 66 to obtain briquettes. The briquettes are obtained by compressing and molding the powdered mixed raw material. A molding aid may be added to the mixed raw material. The shape of the briquettes may be a sphere, a cylinder, a rectangular parallelepiped, an ellipsoid, an almond shape, or the like. As the molding machine 67, a known one may be used, such as a tablet press or a roll type compression granulator.

[0085] The storage tank 68 stores the mixed raw material transferred from the mixer 66 via the molding machine 67. That is, the storage tank 68 stores briquettes. Note that the storage tank 68 may store the mixed raw material transferred from the mixer 66 without passing through the molding machine 67. That is, the storage tank 68 may store the powdered mixed raw material.

[0086] The charger 69 charges the mixed raw material transferred from the storage tank 68 into the melting furnace 70. As the charger 69, a known one is used.

[0087] The melting furnace 70 melts the mixed raw materials transferred from the storage tank 68 to obtain molten glass. The melting furnace 70 is not particularly limited, but includes, for example, a combustion furnace 701, a first burner 702, a second burner 703, a first regenerator 704, and a second regenerator 705, as shown in FIG.

[0088] The combustion furnace 701 includes a melting tank 706 that contains molten glass M. The mixed raw materials are charged into the liquid surface of the molten glass M from above.

[0089] The first burner 702 and the second burner 703 are arranged on either side of the combustion furnace 701, and alternately form a flame F inside the combustion furnace 701. The flame F is formed above the liquid surface of the molten glass M. The mixed raw materials and the molten glass M are heated by the radiant heat of the flame F.

[0090] The first burner 702 mixes fuel and gas, burns them, and forms a flame F. The fuel may be heavy oil, but in this embodiment it is natural gas. The gas may be oxygen gas, but in this embodiment it is air. In this specification, oxygen gas means gas with an oxygen concentration of 90 volume % or more. The second burner 703 also forms a flame F in the same way as the first burner 702.

[0091] The first heat regenerator 704 and the second heat regenerator 705 are disposed on either side of the combustion furnace 701, and recover and store heat from the exhaust gas of the combustion furnace 701. The stored heat is used to heat combustion gas such as air. The first heat regenerator 704 is disposed opposite the second burner 703, and the second heat regenerator 705 is disposed opposite the first burner 702.

[0092] For example, as shown in Fig. 4, when the first burner 702 forms a flame F, the first heat regenerator 704 releases heat stored in advance to heat the combustion gas such as air. At this time, the second heat regenerator 705 collects and stores the heat of the exhaust gas from the combustion furnace 701.

[0093] Similarly, when the second burner 703 forms a flame F, the second heat storage chamber 705 releases heat stored in advance to heat the combustion gas such as air. At this time, the first heat storage chamber 704 collects and stores the heat of the exhaust gas from the combustion furnace 701.

[0094] FIG. 5A shows an example of the heat balance of the melting furnace 70 of FIG. 4 when the heat supply pipe 721 of FIG. 3 is not provided. The meanings of the symbols A, B, C, D, α, and β in FIG. 5A are as follows. A is the amount of heat generated by the combustion of fuel. B is the amount of heat carried by the exhaust gas from the combustion furnace 701 to the first heat regenerator 704 and the second heat regenerator 705. C is the amount of heat heated in the first heat regenerator 704 and the second heat regenerator 705 before the combustion gas such as air is mixed with the fuel. D is the amount of heat carried by the exhaust gas from the first heat regenerator 704 and the second heat regenerator 705 to the outside of the manufacturing apparatus 2. α is the sum of the amount of heat consumed in the process of melting the mixed raw materials and the amount of heat carried by the molten glass M from the melting furnace 70 to the forming apparatus 3. The larger α / A is, the better the heating efficiency is. β is the amount of heat that passes through the furnace walls of the melting furnace 70 and escapes from the melting furnace 70. The sum of A and C is equal to the sum of α, β, and B. Also, B is equal to the sum of C and D. A, B, C, D, α, and β are the amounts of heat per ton of glass.

[0095] FIG. 5B shows an example of the heat balance of the melting furnace 70 in FIG. 4 when the heat supply pipe 721 in FIG. 3 is present. The heat supply pipe 721 in FIG. 3 is an example of the heat supplier 72. The heat supplier 72 supplies heat to the inside of the storage tank 68. The heat supply pipe 721 moves the exhaust gas burned in the melting furnace 70 from the melting furnace 70 to the storage tank 68 together with the heat of the exhaust gas. For example, the heat supply pipe 721 moves the exhaust gas discharged from the first heat regenerator 704 and the second heat regenerator 705 from the melting furnace 70 to the storage tank 68 together with the heat of the exhaust gas. After being heated in the storage tank 68, the mixed raw material is charged into the melting furnace 70 without being returned to room temperature. The residual heat of the exhaust gas can be effectively utilized.

[0096] The symbols A, B, C, D, α, and β in Fig. 5B have the same meanings as the symbols A, B, C, D, α, and β in Fig. 5A. In Fig. 5B, E is the amount of heat brought from the heated mixed raw material in the storage tank 68 to the melting furnace 70. Like A, B, C, D, α, and β, E is also the amount of heat per ton of glass. The sum of A, C, and E is equal to the sum of α, β, and B. Also, B is equal to the sum of C, D, and E.

[0097] According to this embodiment, as described above, the mixed raw material is heated by the residual heat of the exhaust gas in the storage tank 68, and then is charged into the melting furnace 70 without being returned to room temperature. As a result, as shown in Fig. 5B, D is decreased and E is produced, so that A is decreased.

[0098] The reduction in A is greater than that of E, for example 1.5 to 2 times that of E. This is because only a portion of A is absorbed into the mixed raw materials, whereas all of E is absorbed into the mixed raw materials. As A is significantly reduced, fuel consumption is reduced and the amount of carbon dioxide generated is also significantly reduced.

[0099] For example, if a 500°C mixed raw material is fed into the melting furnace 70 instead of a 20°C mixed raw material, it is estimated that A will decrease by 0.9 GJ to 1.2 GJ, and the amount of carbon dioxide generated per ton of glass will decrease by 0.045 to 0.06 tons. In this estimate, it is assumed that 0.05 tons of carbon dioxide is generated per 1 GJ of combustion heat.

[0100] Incidentally, since the mixed raw materials contain NaHCO3 and the like, when they are heated, they generate carbon dioxide gas, as shown in Figure 6. In Figure 6, the horizontal axis is temperature, and the vertical axis is decarbonation rate. The decarbonation rate is the ratio of carbon dioxide gas actually desorbed from the mixed raw materials to the total amount of carbon dioxide gas desorbed from the mixed raw materials in the process of increasing the temperature of the mixed raw materials from room temperature to the melting temperature.

[0101] As the temperature of the mixed raw materials rises from room temperature to 300°C, the reaction shown in formula (3) occurs, and NaHCO3 decomposes into Na2CO3, CO2, and H2O. When the temperature of the mixed raw materials then exceeds 400°C, the reaction shown in formula (4) occurs, and carbonates such as Na2CO3, CaCO3, and MgCO3 decompose to produce carbon dioxide gas.

[0102] The heat supplier 72 supplies heat to the storage tank 68. Inside the storage tank 68, the mixed raw material is heated to a temperature not impairing the fluidity. Inside the storage tank 68, the mixed raw material is heated to, for example, 100°C to 900°C, and preferably 300°C to 800°C.

[0103] If the mixed raw materials are granulated in advance, the fluidity of the mixed raw materials will not be impaired if the temperature of the mixed raw materials is 800°C or less. If the mixed raw materials are granulated in advance and mixed with cullet for use, the fluidity of the mixed raw materials will not be impaired if the temperature of the mixed raw materials is 500°C or less. If the mixed raw materials are not granulated in advance, the fluidity of the mixed raw materials will not be impaired if the temperature of the mixed raw materials is 500°C or less.

[0104] The heat supply pipe 721 transfers the exhaust gas combusted in the melting furnace 70 together with the heat of the exhaust gas from the melting furnace 70 to the storage tank 68. For example, the temperature of the exhaust gas is about 500°C at the outlet of the first heat regenerator 704 or the second heat regenerator 705. Inside the storage tank 68, the mixed raw material is heated to 300°C or higher.

[0105] The mixed raw materials are heated to 300°C or higher in the storage tank 68, and the reaction of formula (3) proceeds inside the storage tank 68, producing carbon dioxide gas. The mixed raw materials are then heated to 1000°C or higher in the melting furnace 70, and the reaction of formula (4) and the like proceeds inside the melting furnace 70, producing carbon dioxide gas.

[0106] The carbon dioxide gas generated by the reaction of formula (4) passes through heat supply pipe 721 and moves from melting furnace 70 to storage tank 68. Heat supply pipe 721 also has the function of moving the carbon dioxide gas in melting furnace 70 from melting furnace 70 to storage tank 68.

[0107] The carbon dioxide gas produced by the reaction of formula (4) and the carbon dioxide gas produced by the reaction of formula (3) are joined inside the storage tank 68. The joined carbon dioxide gas passes through the first gas pipe 81 and moves from the storage tank 68 to the absorption tank 63. The absorption tank 63 absorbs an amount of carbon dioxide gas equivalent to the amount of carbon dioxide gas desorbed from NaHCO3 into the NaOH aqueous solution.

[0108] The first gas pipe 81 transfers the carbon dioxide gas in the storage tank 68 from the storage tank 68 to the absorption tank 63. In the process, the carbon dioxide gas is cooled by heat release or dilution, etc., to a temperature lower than the boiling point of the aqueous solution in the absorption tank 63. The temperature of the carbon dioxide gas at the inlet of the absorption tank 63 is, for example, 50°C to 90°C.

[0109] When the mixed raw materials are granulated in advance and mixed with cullet for use, it is preferable that the temperature of the exhaust gas is 500°C or higher at the inlet of the storage tank 68 and 100 to 300°C at the outlet, since the granulated mixed raw materials and cullet will reach about 500°C.

[0110] The exhaust gas is preferably introduced into the absorption tank 63 at a temperature of 100° C. or higher if it contains water vapor, and at a temperature of the acid dew point or higher if it contains acid gases such as SO2.

[0111] For example, a condenser for removing moisture and acid gas from the exhaust gas may be disposed near the absorption tank 63 of the first gas pipe 81. This can lower the temperature of the exhaust gas and increase the concentration of CO2.

[0112] The first gas pipe 81 transfers the carbon dioxide gas in the storage tank 68 from the storage tank 68 to the absorption tank 63, and transfers a part of the heat of the carbon dioxide gas in the storage tank 68 to the absorption tank 63. It is possible to reduce the power consumption of a heater that heats the aqueous solution in the absorption tank 63. The temperature of the aqueous solution in the absorption tank 63 is adjusted to, for example, 30°C to 90°C in order to efficiently proceed with the reactions of formula (1) and formula (2).

[0113] (First Modification) In the above embodiment, the melting furnace 70 includes a first heat regenerator 704 and a second heat regenerator 705. The first heat regenerator 704 and the second heat regenerator 705 are generally used when the combustion gas is air. Most of the air is nitrogen, which does not contribute to combustion. Therefore, a large amount of air is consumed and a large amount of exhaust gas is generated. The first heat regenerator 704 and the second heat regenerator 705 are used to recover the heat of a large amount of exhaust gas. Note that the number of heat regenerators is not limited to two, and may be one, or three or more.

[0114] When the combustion gas is oxygen gas, the first heat storage chamber 704 and the second heat storage chamber 705 may be used, but are generally not used. When the combustion gas is oxygen gas, the amount of exhaust gas is small, and the construction cost of the heat storage chamber is high, so the heat storage chamber is often not used. Note that when the combustion gas is air, as described above, the heat storage chamber is generally used, but is not required to be used.

[0115] In this modification, the melting furnace 70 does not have a heat regenerator. The following mainly describes the differences between this modification and the above embodiment. Note that the manufacturing apparatus 2 of this modification is the same as the manufacturing apparatus 2 shown in FIG. 3, so it is not shown in the figure.

[0116] The heat supply pipe 721 transfers the exhaust gas combusted in the melting furnace 70 together with the heat of the exhaust gas from the melting furnace 70 to the storage tank 68. According to this modification, since the melting furnace 70 does not have a heat regenerator, the high-temperature exhaust gas carries heat from the combustion furnace 701 to the storage tank 68. The mixed raw materials are heated to a high temperature inside the storage tank 68 by the residual heat of the exhaust gas, and are charged into the melting furnace 70 at a high temperature without being returned to room temperature. However, if the exhaust gas is too hot, the temperature can be lowered by dilution.

[0117] Figure 7 shows the heat balance of the melting furnace 70 according to this modification. The symbols A, B, D, E, α, and β in Figure 7 have the same meanings as the symbols A, B, D, E, α, and β in Figure 5B. According to this modification, C shown in Figure 5B does not exist. Since the mixed raw material can be preheated to a higher temperature by using exhaust gas with a higher temperature, E increases. The sum of A and E is equal to the sum of α, β, and B. Also, B is equal to the sum of D and E.

[0118] According to this modification, E increases, so A decreases further. Fuel consumption decreases further, and the amount of carbon dioxide gas generated decreases further. For example, if a mixed raw material at 800°C is fed into the melting furnace 70 instead of the mixed raw material at 20°C, it is estimated that A decreases by 1.7 GJ to 2.0 GJ, and the amount of carbon dioxide gas generated per ton of glass decreases by 0.085 to 0.1 ton. In this estimation, it is assumed that 0.05 ton of carbon dioxide gas is generated per 1 GJ of combustion heat.

[0119] The mixed raw materials are heated to a high temperature in the storage tank 68. The maximum heating temperature is about 800°C. Therefore, the mixed raw materials are granulated in a molding machine 67 before being transferred to the storage tank 68. Unlike the powdered mixed raw materials, the briquettes obtained by granulation do not lose their fluidity even when heated to about 800°C. This is because the melt generated at the beginning of heating is retained inside the briquettes, suppressing adhesion between the briquettes. When not only the mixed raw materials but also glass cullet is charged into the melting furnace 70, the glass cullet is charged into the melting furnace 70 separately from the mixed raw materials so as not to lose the fluidity of the mixed raw materials.

[0120] Meanwhile, larger gaps are formed between the briquettes than between the powdered mixed raw materials. These gaps can be used as paths for the exhaust gas. Therefore, the briquettes can efficiently absorb the heat of the exhaust gas. This effect can also be obtained when the melting furnace 70 has a heat regenerator. Instead of such direct heat exchange, indirect heat exchange may be used in which the heat of the exhaust gas is indirectly transferred to the mixed raw materials without bringing the mixed raw materials into direct contact with the exhaust gas. In the case of indirect heat exchange, the mixed raw materials may be in powder form.

[0121] (Second Modification) In the above embodiment and the first modified example, the heat supplier 72 has a heat supply pipe 721. The heat supply pipe 721 transfers the exhaust gas combusted in the melting furnace 70 together with the heat of the exhaust gas from the melting furnace 70 to the storage tank 68. The heat supply pipe 721 transfers not only the heat of the exhaust gas but also the carbon dioxide gas of the exhaust gas from the melting furnace 70 to the storage tank 68.

[0122] In this modification, as shown in Fig. 8, the heat supplier 72 has a hot air generator 722. The hot air generator 722 generates hot air separately from the melting furnace 70 and sends it to the storage tank 68. The following mainly describes the differences between this modification and the above embodiment and the like.

[0123] In this modification, a hot air generator 722 is used instead of the heat supply pipe 721. The hot air generator 722 includes, for example, a heating wire that generates heat by electricity and a fan that blows air toward the heating wire. Unlike exhaust gas, the air contains almost no carbon dioxide gas.

[0124] The mixed raw material is thermally decomposed by the heat of the hot air inside the storage tank 68, generating carbon dioxide gas. The generated carbon dioxide gas passes through the first gas pipe 81 and moves from the storage tank 68 to the absorption tank 63, where it is absorbed by the NaOH aqueous solution.

[0125] In the absorption tank 63, the reactions of formula (1) and formula (2) occur, and carbon dioxide gas is absorbed. The temperature of the hot air is adjusted so that the amount of carbon dioxide gas generated by the thermal decomposition of the mixed raw materials is greater than the amount of carbon dioxide gas that is absorbed. This is because there is no heat supply pipe 721, and the carbon dioxide gas in the exhaust gas does not move from the melting furnace 70 to the storage tank 68.

[0126] As shown in Figure 6, the reaction of formula (3) occurs while the temperature of the mixed raw materials is rising from room temperature to 300°C. The reaction of formula (3) is the reverse reaction of the reaction of formula (2). Therefore, the amount of carbon dioxide gas required for the reaction of formula (2) can be obtained by heating up to 300°C.

[0127] The amount of carbon dioxide gas required for the remaining reaction of formula (1) is equal to the amount of carbon dioxide gas required for the reaction of formula (2). In the example shown in Fig. 6, the amount of carbon dioxide gas required in the absorption tank 63 is obtained while the temperature of the mixed raw material is increased from room temperature to 800°C.

[0128] As in the first modification, the mixed raw material is heated to about 800°C inside the storage tank 68. Thereafter, the mixed raw material is charged into the melting furnace 70 at high temperature without being returned to room temperature. Therefore, as in the first modification, the amount of carbon dioxide gas generated due to the combustion of fuel can be reduced.

[0129] In this modification, since there is no heat supply pipe 721, not only the heat of the exhaust gas but also the carbon dioxide gas in the exhaust gas does not move from the melting furnace 70 to the storage tank 68. In this case, the melting furnace 70 may have an electric furnace instead of the combustion furnace 701. The electric furnace uses electricity and does not use fuel such as natural gas. Therefore, it is possible to prevent the generation of carbon dioxide gas due to the combustion of fuel.

[0130] However, when the melting furnace 70 has an electric furnace instead of the combustion furnace 701, the heat supply pipe 721 may be provided. The heat supply pipe 721 can transfer the heat of the exhaust gas from the melting furnace 70 to the storage tank 68. The mixed raw material may be decomposed by the heat of the exhaust gas.

[0131] In the above embodiment and the first modified example, the heat supply pipe 721 is used alone, and in this modified example, the hot air generator 722 is used alone, but the heat supply pipe 721 and the hot air generator 722 may be used in combination. The mixed raw material is decomposed by the heat of the exhaust gas from the melting furnace 70 and the heat of the hot air from the hot air generator 722.

[0132] The hot air generator 722 of this modified example includes a heating wire that generates heat by electricity and a fan that blows air toward the heating wire, but the technology of the present disclosure is not limited to this. For example, the hot air generator 722 may include a burner that injects fuel and gas and forms a flame. Carbon dioxide gas is generated by burning fuel that contains carbon, so the temperature of the hot air can be low. The temperature of the hot air is adjusted so that the required amount of carbon dioxide gas can be generated by the pyrolysis of the mixed raw material and the combustion of the fuel. When burning fuel that contains hydrogen and ammonia, it is possible to prevent an increase in CO2 because it does not contain carbon.

[0133] (Third Modification) The manufacturing apparatus 2 in the above embodiment, the above first modification, and the above second modification has a heat supplier 72. The heat supplier 72 supplies heat to the storage tank 68. The mixed raw material is heated inside the storage tank 68, and then is charged into the melting furnace 70 at a high temperature without being returned to room temperature. This reduces the amount of fuel consumed and reduces the amount of carbon dioxide gas generated due to the combustion of the fuel.

[0134] As shown in Fig. 9, the manufacturing apparatus 2 of this modified example does not have a heat supplier 72. The mixed raw material is directly charged into the melting furnace 70 without being heated inside the storage tank 68. Inside the melting furnace 70, the reaction of formula (3) and the reaction of formula (4) occur. Below, the differences between this modified example and the above embodiment and the like will be mainly described.

[0135] In this modification, the thermal decomposition of the mixed raw materials does not proceed inside the storage tank 68, and carbon dioxide gas is not generated. The thermal decomposition of the mixed raw materials proceeds inside the melting furnace 70. Therefore, the second gas pipe 82 transfers the carbon dioxide gas in the melting furnace 70 from the melting furnace 70 to the absorption tank 63, instead of the storage tank 68. As in the above embodiment, the amount of carbon dioxide gas generated due to the thermal decomposition of the mixed raw materials is reduced.

[0136] The second gas pipe 82 transfers the carbon dioxide gas in the melting furnace 70 from the melting furnace 70 to the absorption tank 63. In the process, the carbon dioxide gas is cooled by heat radiation, dilution, etc., and is cooled to a temperature lower than the boiling point of the aqueous solution in the absorption tank 63. The temperature of the carbon dioxide gas at the inlet of the absorption tank 63 is, for example, 50°C to 90°C.

[0137] The second gas pipe 82 transfers the carbon dioxide gas in the storage tank 68 from the storage tank 68 to the absorption tank 63 , and transfers a portion of the heat of the carbon dioxide gas in the storage tank 68 to the absorption tank 63 .

[0138] The method for producing a mixed raw material, the method for producing molten glass, the method for producing a glass article, the apparatus for producing molten glass, and the apparatus for producing a glass article according to the present disclosure have been described above, but the present disclosure is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure.

[0139] This application claims priority based on Japanese Patent Application No. 2019-193025, filed with the Japan Patent Office on October 23, 2019, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0140] 1. Glass product manufacturing equipment 2 Molten glass manufacturing equipment 3 Molding equipment 4. Slow cooling device 5 Processing equipment 61 Raw material tank 62 Aqueous solution tank 63 Absorption tank 66 Mixer 68 Storage Tank 69 Loading machine 70 Melting Furnace M Molten Glass

Claims

1. a raw material tank for accommodating glass raw materials; an aqueous solution tank for storing an aqueous solution of sodium hydroxide; an absorption tank in which the aqueous solution transferred from the aqueous solution tank absorbs carbon dioxide gas to precipitate sodium hydrogen carbonate; a mixer that mixes the glass raw material transferred from the raw material tank with the sodium hydrogen carbonate transferred from the absorption tank to obtain a mixed raw material; A storage tank for storing the mixed raw material transferred from the mixer; a melting furnace for melting the mixed raw material transferred from the storage tank to obtain molten glass; Including, The absorption tank includes a first tank in which carbon dioxide gas is absorbed into the aqueous solution to obtain sodium carbonate, a second tank in which carbon dioxide gas is further absorbed into the aqueous solution transferred from the first tank to obtain the sodium bicarbonate in the aqueous solution, and an internal piping for transferring carbon dioxide gas remaining in the second tank to the first tank.

2. 2. The apparatus of claim 1, further comprising a heat supplier that supplies heat to the storage tank to convert the sodium bicarbonate into sodium carbonate within the storage tank and obtain carbon dioxide gas that is absorbed in the absorption tank.

3. a raw material tank for accommodating glass raw materials; an aqueous solution tank for storing an aqueous solution of sodium hydroxide; an absorption tank in which the aqueous solution transferred from the aqueous solution tank absorbs carbon dioxide gas to precipitate sodium hydrogen carbonate; a mixer that mixes the glass raw material transferred from the raw material tank with the sodium hydrogen carbonate transferred from the absorption tank to obtain a mixed raw material; A storage tank for storing the mixed raw material transferred from the mixer; a melting furnace for melting the mixed raw material transferred from the storage tank to obtain molten glass; Including, The apparatus for producing molten glass further includes a heat supplier that supplies heat to the storage tank to convert the sodium bicarbonate into sodium carbonate inside the storage tank and obtain carbon dioxide gas that is absorbed in the absorption tank.

4. 4. The apparatus according to claim 2, wherein the heat supplier includes a heat supply pipe for transferring exhaust gas combusted in the melting furnace together with heat of the exhaust gas from the melting furnace to the storage tank.

5. The apparatus according to claim 2 , wherein the heat supplier includes a hot air generator that generates hot air separately from the melting furnace and sends the hot air into the storage tank.

6. 6. The apparatus according to claim 2, further comprising a first gas pipe for transferring carbon dioxide gas in the storage tank from the storage tank to the absorption tank.

7. 7. The apparatus according to claim 1, further comprising a second gas pipe for transferring carbon dioxide gas from the melting furnace to the absorption tank.

8. The apparatus according to claim 1 , further comprising a molding machine between the storage tank and the mixer for granulating the mixed raw material to obtain briquettes.

9. An apparatus for producing molten glass according to any one of claims 1 to 8, a forming device for forming the molten glass obtained in the melting furnace; an annealing device for annealing the formed glass; a processing device for processing the annealed glass into a glass article; The manufacturing apparatus for a glass article comprises:

10. A method for producing molten glass, comprising using an apparatus as claimed in any one of claims 1 to 8 to obtain molten glass.

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