KR20160022872A - Controlling glassmelting furnace operation - Google Patents

Abstract

In a method of operation of a glass melting furnace 100 including a melting zone 11 and a purification zone 12, the melting zone is provided with a plurality of pairs of opposing regenerators 41, 42. One or more gaseous streams or atomizing fluid streams of the fuel and one or more oxidant streams are injected and combusted, for example, through injectors 32, 33 into the refinery zone above the molten glass manufacturing material, The average oxygen concentration in the atmosphere near the surface of the bath increases by 1 to 60% by volume. The fuel and combustion air flow rates of each of the regenerator ports are such that the oxygen concentration in the flue gas discharged from each regenerator port located between the spring zone and the purification zone 12 in the melt zone 11 is between 2 and 10 vol% . Oxidized glass can be produced and the corrosion potential of the crown is reduced.

Description

CONTROLLING GLASSMELTING FURNACE OPERATION [0002]

The present invention relates to the operation of a glass melting furnace in which a glass manufacturing component is melted to produce a bath of molten glass manufacturing material from which solid glass can be produced.

In the production of glass, the glass manufacturing material is melted in the glass melting furnace by heat provided from a burner which burns the fuel with oxygen. The fuel may be combusted with the air as the oxygen source, or with the stream containing an oxygen content higher than the oxygen content of the air. The furnace should be made of materials that can withstand the dominant super-high temperatures in the furnace. Commonly used structural materials are well known and typically include AZS and silica refractories and related materials.

However, it is known that the conditions in the glass melting furnace cause corrosion of the inner surface of the furnace, especially the roof ("crown") on the glass manufacturing material. The most widely used material for crown is silica bricks for soda-lime-silicate glass furnaces. Alkali vapors (mainly NaOH and KOH) generated from the glass batch material and the molten glass in the glass melting furnace react with the silica refractory bricks and form a vitreous silicate material on the inner surface of the crown over time. When sufficient concentrations of alkali oxides (mainly Na ₂ O and K ₂ O) accumulate in the glassy silicate layer, the glassy material falls directly onto the melted glass in the furnace or flows along the silica refractory surface and also onto other refractory surfaces in the furnace A portion of the refractory particles may be dissolved or removed and the fluid may be sufficient to cause the particles to fall into the molten glass. Such corrosion is undesirable because corrosion causes loss of crown material, which in turn leads to costly crown maintenance or replacement, and also because the corrosion product is a pool of molten glass material in the furnace, ≪ / RTI > and is known to cause defects in glassware.

The present invention reduces the corrosion of refractories and also improves the quality of the glass, in particular by increasing the oxidation state of the glass, i. E. Reducing the redox ratio, the molar ratio of ferrous to ferric iron, The present invention provides a methodology for controlling the furnace atmosphere that produces a glass characterized by a high light transmission rate for applications such as tableware. Preferably, the redox reduction ratio is reduced by 0.01 to 0.20.

One aspect of the present invention is a method of operating a glass melting furnace comprising a glass melting chamber defined by opposing sidewalls, a back wall, a roof, and a front wall, the method comprising:

(A) by the heat from the two or more pairs of opposing regenerator ports at said sidewalls of the melting zone and by the heat provided to said melting zone by combustion of the preheated oxidizing agent, Establishing a bath of molten glass-making material that melts in the melting zone of the chamber, wherein the combustion creates an atmosphere comprising combustion products in the melting zone above the bath, wherein a spring zone is present in the bath ,

(B) the molten glass manufacturing material passes from the melting zone of the glass melting chamber to the purification zone, and through the purification zone, out of the glass melting chamber through the port at the front wall,

(C) injecting at least one gaseous stream or atomizing fluid stream of fuel and at least one oxidant stream into a refinery zone on top of the molten glass manufacturing material and combusting the fuel and oxidant in the refinery zone, The average oxygen concentration in the atmosphere near the surface of the bath increases by 1 to 60% by volume,

(D) the fuel and combustion air flow rates of each of the regenerator ports are such that the oxygen concentration in the flue gas discharged from each of the regenerator ports located between the spring zone and the refinery zone is between 2 and 10 vol%, preferably between 2 and 6 vol% % To be adjusted

.

In a preferred aspect of the invention, the at least one oxidant stream injected in step (C) comprises from 35% to 100% by volume oxygen and the fuel is between 110% and 2000% Is injected in step (C) with a stoichiometric ratio to the oxidant.

As used herein, "glass-making material" includes any of the following materials and mixtures thereof: sand (mainly SiO ₂ ), soda ash (mainly Na ₂ CO ₃ ), limestone (mainly CaCO ₃ and MgCO ₃ ) (E.g., recycled solid pieces of glass) by melting and solidifying any of the above oxides, borax (hydrated sodium borate), other oxides, hydroxides and / or silicates of sodium and potassium. Glass making materials are also functional additives, such as batch oxidizing agent, for example salt cake (sodium sulfate, Na ₂ SO ₄₎ and / or foundation (sodium nitrate, NaNO _3, and / or potassium nitrate, KNO _3), and a refining agent, such as oxidation It may include antimony (Sb ₂ O _3).

As used herein, "alkali species" include sodium hydroxide, potassium hydroxide, products formed by the decomposition of sodium hydroxide or potassium hydroxide at temperatures above 1200 ° C, and mixtures thereof, including but not limited to sodium , ≪ / RTI > potassium and / or lithium atoms.

As used herein, an "oxygen-fuel combustion device" refers to an oxidant having an oxygen content that is higher than the oxygen content of the air, preferably greater than 50 vol%, more preferably greater than 90 vol% Means a combustion device.

As used herein, "oxygen-fuel combustion" means the combustion of an oxidant and fuel having an oxygen content of greater than 50 vol%, more preferably greater than 90 vol%, with an oxygen content greater than the oxygen content of the air do.

As used herein, the "atmosphere near the roughened surface" means a gas phase layer that spans one foot above the roughened surface from the roughened surface.

1 is a top plan view of a glass melting furnace in which the present invention may be practiced.
Fig. 2 schematically illustrates gas flow in the furnace of Fig. 1 when operated without the invention. Fig.
Figure 3 schematically illustrates gas flow in the furnace of Figure 1 when operated in accordance with one embodiment of the present invention.
Fig. 4 is a graphical representation of the oxygen concentration profile (wet volume%) of the furnace atmosphere near the glass melt surface in the furnace of Fig. 1 when operating without the present invention in the manner shown in Fig.
Fig. 5 is a graphical representation of the oxygen concentration profile (wet volume%) of the furnace atmosphere near the glass melt surface in the furnace of Fig. 1 when operated in accordance with the embodiment of the present invention shown in Fig.
Figure 6 is a top plan view of a glass melting furnace showing an alternative arrangement of injecting gas into the furnace of Figure 1, in accordance with another embodiment of the present invention.
7 is a side cross-sectional view of a glass melting furnace showing an operation of arbitrarily supplying gas bubbles to melted glass.
8 is a side cross-sectional view of a glass melting furnace showing the flow of molten glass and the spring zone.

Referring first to glass manufacturing itself, FIG. 1 shows a top plan view of a typical cross-fired float glass furnace 100 with a regenerator to which the present invention may be applied. The present invention is not limited to a float glass furnace, but can be embodied in other types of glass melting furnaces, for example, tableware glass, plate glass, display glass, and container glass. The furnace (100) includes a melting zone (11) and a purification zone (12). The melting zone 11 and the refining zone 12 are surrounded by the back wall 21, the front wall 23 and the side wall 22. A crown or roof (not shown) is connected to side wall 22, back wall 21, and front wall 23. The furnace 100 also has a bottom which, together with the rear wall 21, the side wall 22 and the front wall 23 and the crown or roof, forms an enclosure holding the molten glass manufacturing material.

The conditioning zone 13 includes not only crown or roof (not shown) connected to side wall 24, front wall 25, end wall 26, and side wall 24, front wall 25 and end wall 26 Not the bottom, and is surrounded by crown or roof. The conditioning zone 13 (if present) is connected to the purification zone 12 to receive the molten glass manufacturing material flowing from the purification zone 12 for further conditioning in a manner already familiar in the relevant art of the molten material . The waist section 14 is a narrow passage connecting the purification section 12 and the conditioning section 13.

Although the particular shape of the bottom portion is not critical, it is generally preferred that at least a portion of the bottom portion is flat and the flow direction of the molten glass passing through the furnace is horizontal or inclined. All or part of the bottom may instead be curved. As long as the wall retains the desired amount of molten glass and is sufficiently high to provide an upper space (below the crown) of molten glass in which combustion can occur where it melts the glass manufacturing material and keeps it molten, The specific shape of the furnace defined by the walls is also not important.

The furnace 100 is also supplied with the glass manufacturing material into the melting zone 11 along the inner surface of the back wall 21 or in the side wall 22 near the back wall 21 in the case of other types of glass furnaces (Not shown) that can be used to charge the material. There may also be one or more flues in which the combustion products of fuel and oxygen (in the melting zone 11) can flow from the interior of the furnace. The years or years are typically located on the back wall 21, or on one or more sidewalls.

The bottom, sides and crown of the furnace should be made of a refractory material which is capable of maintaining its solid structure integrity at the temperature at which it is exposed, i.e. typically between 1300 ° C and 1700 ° C. Such materials are well known in the field of structural engineering of high temperature devices. Examples include silica, fused alumina, and AZS.

The inner surface of the crown, that is, the surface in contact with the furnace atmosphere, may be comprised of the original structural material of the crown, and may instead include a slag layer formed at a portion that was the noncorrosive surface of the crown. These slag layers are typically formed due to the reaction of dust and volatile vapors from glass making materials and molten glass, and can often be found in furnaces that have already been used. Typically, the slag layer contains silica, an alkali oxide, an alkaline earth oxide, and compounds thereof, and contains, for example, calcium oxide and / or calcium oxide and a compound of silica and / or an alkali oxide. Accordingly, the present invention provides a process for preparing a crown comprising a furnace in which the inner surface of the crown comprises a corrosion product formed by the reaction of the surface with an alkali hydroxide, and a furnace wherein the inner surface of the crown does not contain a corrosion product formed by reaction of the surface with an alkali hydroxide Lt; / RTI >

The melting zone 11 includes two or more pairs of opposing regenerator ports on the side wall 22. "Opposite" means that in a given regenerator port pair, there is one port on each sidewall 22, facing each other, both facing the interior of the melting zone 11. The opposed ports are preferably essentially coaxial, i. E. These ports are facing directly opposite each other; Although an offset port where each axis of the ports is not coaxial with the rest of the ports may be used, it is not desirable. Combustion occurs in the melting zone 11 when natural gas or fuel oil, which is injected at or near the position where these ports open to the melting zone 11, is mixed with the hot combustion air from the regenerators 41 and 42 So that a flame is formed and heat is generated in the melting zone to melt the glass manufacturing material and keep the glass manufacturing material in a molten state. The regenerator ports are in communication with regenerators 41 and 42 as further described below. The port on one side of the melting zone is numbered 1L to 6L and the port on the other side of the melting zone is labeled 1R to 6R Numbered. Depending on the desired glass melting capability of the furnace, any number of ports of 2 to 10, or even 20, or more, may be used. One or more fuel injectors (not shown) are located at or near the outlet of each port to form a flame (not shown) and inject fuel to generate heat in the melting zone 11. The fusing zone 11 is located closest to the front wall 23 when the fuel injector is located closer to the front wall 23 than between the rear wall 21 and the last regenerator port pair closest to the front wall 23, Lt; / RTI > is defined as the area between the fuel injectors for the last regenerator port pair.

Optionally, one or more flue gas ports (not shown) that are not connected to the regenerators 41 and 42 are located in one or more walls of the fusing zone 11 or the purification zone 12, A part of the flue gas can be exhausted.

The arrows 30 and 31 between the rear wall 21 and the ports 1L and 1R represent an optional oxygen-fuel combustion device which is often used to increase production and / or glass quality in a glass furnace.

Referring to Fig. 7, the molten zone 11 optionally has a gas bubble generator installed through the bottom of the furnace to improve the circulation of melted glass. Air or oxygen from a source 74 (e.g., a storage tank or cylinder) is injected through each bubble generator 72 to penetrate the surface of the molten glass to form giant bubbles 71 ). Preferably, the gas is a gas into which oxygen is injected through the bubbler. The flow of gas through the bubble generator is controlled by a controller 73 which allows the operator to adjust the flow of the gas to a flow rate of, for example, 1-10 SCFH.

The purification zone 12 is characterized in that it can optionally have an apparatus for burning additional fuel and oxidant on the molten glass manufacturing material. Preferably, however, the regenerator port is not present in the sidewalls and end walls contained in the purification zone.

The molten glass manufacturing material in the melting zone 11 and the refining zone 12 undergoes a complicated recirculating flow pattern in the furnace and is discharged from the melting zone 11 through the refining zone 12 to the port Preferably through a net flow in the direction towards the conditioning zone (13). 8, two gigantic recirculating flows 82 and 83 of molten glass in a typical glass furnace are formed in the longitudinal direction of the furnace, and they form a so-called spring zone 81, which is typically found near the top zone of the furnace ). A first circulation loop (82) is formed between the spring region (81) and the rear wall (21). The molten glass near the upper surface flows backward from the spring region 81 toward the rear wall 21 and then downwardly near the rear wall 21 and then travels toward the spring region 81. Near the spring zone 81, the molten glass flows upward and most of the glass is retrograded toward the rear wall 21. Numerous gas bubbles float from the spring zone to the upper surface of the glass vessel and are removed, that is, the glass is refined. A portion 84 of the refined glass travels from the spring zone 81 toward the front wall 23 and passes through the waist region 14 to the conditioning zone 13. In the second glass circulation loop 83 some of the glass from the conditioning zone 13 flows back toward the spring zone 81 into the purification zone 12 near the bottom of the waist zone 14. Near the spring zone 81, the glass flows upwardly, merging with the glass flowing from the rear wall 21, and part of the glass circulates in a direction toward the front wall 23. Thus, the "spring zone" is defined between the circulating flow 82 of molten glass passing adjacent the rear wall of the furnace and the circulating flow 83 of molten glass passing adjacent the front wall 23 of the furnace, It is the area in the molten glass in the melting furnace. While the molten glass is in the molten zone 11 and the refinery zone 12, the dissolved gas can rise to the bath surface to escape the bath and the less volatile material can be more uniformly distributed within the bath have.

In operation, the glass manufacturing material is supplied to the melting zone 11. The combustion in the melting zone 11 provides heat to melt the glass manufacturing material in the melting zone and to maintain the resulting bath of molten glass manufacturing material in the molten state. This combustion may be effected by the combustion of oxygen, which is provided as an oxygen-enriched air or stream, typically provided as air, or optionally containing between 50% and 99% by volume oxygen, with a fuel, preferably a natural gas or oil Lt; / RTI > The amount of fuel and oxygen to be supplied and combusted should be sufficient to provide sufficient heat to melt the glass-making material supplied to the melting zone 11.

When combustion is performed in the fusing zone 11 using a regenerator, fuel (not shown in FIG. 1) typically flows from below the ports at or near the port outlets, . The combustion air is preheated in a regenerator (e.g., regenerator 41) on the same side of the melting zone 11 to flow to the melting zone 11 and mixed with the injected fuel to form a flame, The gaseous combustion products are withdrawn from the melting zone 11 via a port in the other side wall 22 of the melting zone 11 via another regenerator (regenerator 42 in this figure). The gaseous oxidant (i. E., Air, oxygen-enriched air, or higher purity oxygen) represented by stream 43 passes through the regenerator and passes from the hot gaseous combustion products that had been withdrawn through the regenerator in the previous cycle After being heated by the transfer of the absorbed heat, the oxidizing agent is burned with the fuel in the melting zone 11. The hot gaseous product taken out through the port communicating with the regenerator 42 is discharged to the other regenerator 41 while the combustion of the fuel and the oxidizer supplied at or through the port communicating with the regenerator 41 occurs in the melting zone 11. [ (42). The regenerator is typically made of refractory bricks or other materials capable of absorbing heat at the existing high temperatures (optionally, the regenerator also contains additional objects such as balls or blocks of refractory material to absorb heat from the hot combustion gases Lt; / RTI >

(Typically air) for combustion from another regenerator (i. E. Regenerator 42) flows into the melting zone 11 and the regenerator (e. G. Combustion is generated together with the fuel injected from the same side as that of the regenerator 41, and the generated high-temperature gaseous combustion products are taken out through the port connected to the regenerator 41. At this time, the oxidizing agent involved in the combustion in the melting zone 11 passes through the regenerator 42 and is heated by heat transfer from the regenerator 42, which is stored in the previous cycle. After another time, the combustion air flow and the fuel injection direction are reversed again. The regenerator labeled 41 and 42 may be one common chamber on each side of the melting zone 41 or it may be a separate distinct number communicating with one port connected to the melting zone 11 of the furnace Lt; / RTI >

In some types of glass melting furnaces, a gas (typically, air) stream 50 flows through the port 28 in the front wall 23 to the refining zone 12 in a direction toward the melting zone 11. This stream 50 is typically part of the air that cools the bath of molten glass in the conditioning zone 13. In a conventional implementation that does not use the present invention, the stream 50 flows into the melting zone 11 via the purification zone 12. The conditioning zone 13 is preferably, but not essential, in the present invention. When the conditioning zone 13 is used, the cooling gas stream 52 is supplied to the conditioning zone 13 through four openings in the wall 24, as shown for example by four arrows, A portion of the cooling gas 52 then flows into the purification zone 12 via the conditioning zone 13 through the port 28 in the waist region 14 as the gas stream 50. The remaining cooling gas 52 is exhausted through an exhaust port (not shown) located in the conditioning zone 13 or the waist zone 14.

In another type of glass melting furnace, the port 28 is submerged under the molten glass so that only molten glass flows through the port 28, so that the gas does not flow through the port 28 into the refining zone 12 . In this type of furnace, some air may enter the purification zone through another opening.

Arrows 32 and 33 in the purification zone 12 represent locations where one or more gaseous streams are injected in accordance with the present invention. These locations are in the purification zone 12. The preferred position is that between the front wall 23 and the regenerator port closest to the front wall 23 or between the front wall 23 and the front wall 23 when the fuel injection port is closer to the front wall 23 than to the regenerator port to which it is connected Between adjacent such fuel injection ports). A more preferred location is near the regenerator port or the fuel injection port. Continuous gas injection from both injectors of the pair of opposed injectors 32 and 33 constitutes a preferred embodiment of the present invention, but the present invention also contemplates the use of a single injector, preferably a regenerator Lt; RTI ID = 0.0 > sidewall < / RTI > That is, if the regenerator 42 is cyclically in the ignition cycle, the gas will be injected from the injector 32, and if the regenerator 41 is in the ignition cycle, injection from the injector 33 will continue. Each injector 32 or 33 may be an oxygen-fuel combustion device that is fed with fuel (e.g., natural gas) and oxygen, which are combusted in the purification zone 12 to form a flame within the furnace. Each injector may include a single injector or may include a plurality of injection nozzles or ports into which different gases or atomized oils may be injected, located on the side wall 22. [ Preferred injectors have two injection ports that are vertically fixed in sequence (as shown and disclosed in U.S. Patent No. 5,924,848). Alternatively, each injector 32 and 33 can inject (non-burning) oxygen alone, air alone, oxygen-enriched air, or a gas mixture of any suitable composition. When gas is injected from more than one injector, such as injectors 32 and 33, the gas injected from any injector may have a different or the same composition as the gas injected from any other injector. Optionally, one or more streams of purge gases 55-58 flow into the purification zone 12 through openings located in the front wall 23 and / or sidewall 22. This purge gas stream, preferably oxygen, oxygen enriched air or air, increases the oxygen concentration in the atmosphere in the purification zone 12 when oxidized glass is produced.

In the cross-fired regenerative glass melting furnace as shown in Fig. 1, the furnace gas circulation pattern in the melting zone 11 principally includes the combustion oxidant (air) injected into the melting zone 11 and the momentum of the fuel . If the present invention is not practiced, the combustion of the oxidant and fuel (and, if present, the effect of the gaseous stream 50 or other gas stream flowing into the purification zone 12) in the molten zone, 1 between the ports 6L and 6R and the front wall 23 of the last regenerator port pair which circulates from the melting zone 11 to the refining zone 12 and back to the melting zone 11, Influencing the establishment of recirculating gas flow patterns. If the regenerator 41 is in the ignition cycle, the recirculation flow direction in the purification zone 12 (represented by circle 61 in FIG. 2) is counterclockwise and if the other regenerator is in the ignition cycle instead, the pattern is reversed The recirculation flow direction is clockwise. If no other gas is injected into the purification zone 12, the gas composition in this recirculating gas flow pattern will be such that the gaseous combustion products typically contain 1-3 vol% O ₂ (i.e., Which is very similar to that of the first embodiment. When the cooling gas 50 flows into the purification zone as described herein, the atmosphere composition of the purification zone 12 is determined by the mixing pattern of the cooling air flowing into the purification zone 12 and the furnace gas circulating to the purification zone do.

Figure 3 illustrates the gas flow pattern when the present invention is implemented using a pair of opposed oxygen-oil combustion devices located on the sidewall 22. The atomized fuel oil and oxygen are simultaneously injected as two opposing jets. The flow of gas circulating from the fusing zone 11 to the purification zone 12 is greatly reduced, instead of the gas flow circulating throughout the purification zone 12, as shown at 61 in FIG. The gas flow from the melting zone to the purification zone may be reduced by 10% or more, preferably by 20 or 25% or more, more preferably by 40 or 50% or more. The reduction amount can be determined by comparing the oxygen content in the atmosphere in the purification zone before and after the practice of the present invention. The practice of the present invention increases the oxygen content in the refinery zone atmosphere in proportion to the extent that the melt zone atmosphere can not flow into the refinery zone and can not result in dilution (in oxygen content) of the refinery zone atmosphere.

Application of computer fluid dynamics analysis to a typical 600 metric tpd float glass furnace (12.2 m x 38.2 m wide furnace body) of the type shown in Figure 1, when operated without the present invention, The oxygen concentration profile (wet volume%) of the sample was predicted as shown in Fig. When the stream 50 (air) of 1,719 Nm ³ / hr, which had about 21% O ₂ in the port 28 in the wall 23, flows into the purification zone 12, The local O ₂ concentration of the sidewall 22 and the front wall 23 decreased by as much as 4% at the edge formed by the sidewall 22 and the front wall 23. An optional purge gas stream 55-58 was not injected in this example. The low local O ₂ concentration in the purification zone 12 was caused by mixing with a circulating furnace containing about 2% O ₂ . The oxygen concentration in most of the purification zones 12 was less than 10% except for a small area near the port 28 in the wall 23. The average oxygen concentration in the purification zone was estimated to be about 5%. The gas circulation pattern in the purification zone 12 was driven mainly by the momentum of the combustion oxidant (air) and the fuel injected from the port 6 and the port 5 into the melting zone 11. The total momentum of the combustion oxidant and fuel ignited at port 6 was 5.58 kg m / s ² .

Fig. 5 is a graphical representation of the oxygen concentration profile (wet volume%) of the furnace atmosphere near the glass melt surface in the furnace of Fig. 1 when operated in accordance with the embodiment of the present invention shown in Fig. Fuel combustion device pair of the type disclosed in U.S. Patent No. 5,601,425 is used as injectors 32 and 33 from the axis of the port 6 (the axis of the ports 6L and 6R) to the axis of the injector in the purification zone is 2.475 m. < / RTI > Reduced the firing rate of the port 6, which reduced the total momentum of the port 6 to 3.4 kg m / s < ^{2 &} gt ;. The total momentum of combustion oxidant and fuel oil and atomizing air ignited from each injector 32 and 33 was 8.3 kg m / s ² . The combustion stoichiometric ratio of fuel oil versus oxidant and atomized air was set to produce a combustion product with O ₂ in excess of 2 volume percent on a wet basis. (Port 6 + injector 32) / (injector 33) was 1.4 in this embodiment.

It was confirmed by the computer fluid dynamics model of the glass furnace that the lowest local O ₂ concentration was about 10% by volume near the edge formed by the sidewall 22 and front wall 23 of the purification zone. Except for a small area near the port 28 in the wall 23, the oxygen concentration in most refinery areas is between 10% and 16% by volume. The average oxygen concentration in the purification zone was estimated to be about 14%, which is surprisingly large when compared to the estimated average concentration of about 5% for the conditions shown in FIG. 1 when operating without the present invention to be. Since the combustion stoichiometric ratio of the oxygen-fuel combustion device is set to produce O ₂ in excess of 2% on a wet basis in the combustion products, the simple mixing of the combustion products from the oxygen-fuel combustion device results in an average oxygen concentration . Without wishing to be bound by any particular theory, this observation is based on the fact that since the jet momentum of the two opposing jets or flames from the injectors 32 and 33 is sufficiently large compared to the flames from the ports 6L and 6R, ) To the purification zone 12 is reduced to increase the average oxygen concentration in the atmosphere in the purification zone.

The location and momentum of each gas stream from the injectors 32 and 33 is selected so that the circulation of gas phase combustion products from the melting zone 11 to the purification zone 12 is reduced, and preferably minimized. Preferably, the ratio of the total momentum of the port 6 to the total momentum of the injector 32 to the total momentum of the injector 33 is 0.25 to 3.0, more preferably 0.5 to 2.0.

The reduction of circulation of this product from the melting zone 11 to the purification zone 12, as the gaseous combustion products contain considerable concentrations of alkaline vapors (mainly NaOH and KOH), suggests that the conditions of the purification zone are the volatilization of the alkaline vapors As long as it is set to minimize the concentration of alkali vapor in the purification zone 12. In this way, the present invention facilitates reduction of glass defects caused by alkali corrosion of the silica-based structural material of the crown. This also improves the oxidation state of the glass by the average oxygen concentration higher than in the refining zone, and reducing the color of glass defects caused by the low O ₂ concentration in the refining zone. Since the glass is further oxidized and the redox ratio is reduced by the present invention, the present invention is advantageous for the production of highly oxidized glass such as, for example, sheet glasses and glassware useful in solar panel applications.

The present invention contemplates reducing or minimizing the mixing of the furnace gas from the melting zone 11 to the refinery zone 12 and providing the gas stream 50 (e.g., air) (i.e., ) And the optional purging gas stream 55-58 into the purification zone 12.

Instead of using two successively flowing injectors 32 and 33, for example a pair of opposed oxygen-fuel combustion devices, it is possible to cross flow from the injectors 32 and 33 so that gas flows one at a time from these injectors And flow from a single jet is used which is on the side of the furnace opposite the side from which the flame originates from the port 6. The momentum of the single jet is preferably within 25 to 300%, more preferably 50 to 200% of the momentum of the flame from the port 6. The angle of the single jet is preferably set toward the ignition side of the port 6 or parallel to the front wall 23.

Whether injectors 32 and 33 are injected together or injected at an intersection, a preferred embodiment of the present invention is to inject air or an oxidant containing 21 to 100 vol% O ₂ . More preferably, the oxygen concentration of the oxidant is 33 to 100% by volume, and most preferably the oxygen concentration of the oxidant is 85 to 100% by volume. Injector stoichiometric ratio of the flame injected from the gas composition and / or injectors 32 and 33 injected from the 32 and 33 is the different from each other, it can affect the temperature and O ₂ concentration profiles of the purification zone 12 have. By injecting an oxidant containing O ₂ at a concentration higher than the average O ₂ concentration in the purification zone without injecting fuel consuming oxygen by the combustion reaction, the oxygen concentration in the purification zone is significantly increased by the present invention do. For example, a typical average oxygen concentration of the oxygen in the refining zone of a glass furnace for producing a flat glass is an O ₂ of 1% by volume to 6% by volume based on the humidification amount in the range. Injectors 32 and 33 are either injected into either or intersection injection, a preferred embodiment of the invention the oxygen-average concentration in the refining zone from 1 to 60% by volume (O ₂₎ in the humidification amount based on 2% by volume to 60 increases with And an oxidizing agent is injected to form an atmosphere containing O ₂ by volume%. More preferably, 21 to 100% by volume of O ₂ is injected and optionally preheated air or oxidant is injected to increase the oxygen average concentration in the purification zone by 1 to 40% by volume (O ₂ ) To form an atmosphere containing ₂ % by volume to 40% by volume of O ₂ . Most preferably, 21 to 100% by volume of O ₂ is injected and optionally preheated air or oxidant is injected to increase the oxygen average concentration in the purification zone by 2 to 20% by volume (O ₂ ) To form an atmosphere containing 3 vol% to 20 vol% O ₂ . The oxygen average concentration in any given area, e.g. near the rough surface, is determined by measuring the oxygen concentration value at two or more locations within a given area and averaging the measurements.

When a large amount of oxidant is injected, a cooling effect occurs in the purification zone. Cooling of the purification zone can promote condensation on the furnace wall and roof of the purification zone of the volatile alkali species and can lead to glass defects due to the flow of potentially condensed material into the glass melt. Thus, it is preferable to preheat, preferably at +/- 500 < 0 > F of the purification zone temperature, before the oxidant is injected. Because the typical temperature of the purification zone is 2500-2900 [deg.] F, it is difficult to preheat the oxidant to or above the temperature of the purification zone due to the temperature limitations of conventional gas preheat systems. A preferred method of producing high temperature streams containing high oxygen concentrations without the use of conventional indirect heat exchangers is disclosed in U.S. Patent No. 5,266,024, which discloses an in- It is disclosed to produce a hot gaseous oxygen stream which can be burned and injected into a furnace.

Another preferred method of preventing the cooling effect is to generate a heat by injecting under stoichiometric conditions, that is increased with a small amount of fuel and a large amount of the oxidant from the combustion device, and also to form the atmosphere of a high O ₂ concentration. For example, if natural gas and oxygen are injected at a stoichiometric ratio of 500% (i.e., 5: 1 O ₂ vs. fuel on a molar basis), i.e., approximately 1 volume of natural gas to 10 volumes of pure O ₂ , The adiabatic flame temperature is about 3400 ℉ and the O ₂ concentration in the combustion products is about 72% on a wet basis. This example of fuel and oxidant gas injection under increased stoichiometric combustion conditions will result in a gentle heating effect, since the temperature of the purification zone is typically less than 2800 [deg.] F. By adjusting the stoichiometric ratio, the heating and cooling effects of the gas injection can be controlled to maintain the optimum glass quality while substantially increasing the O ₂ concentration in the atmosphere in the purification zone. The preferred range of the increased stoichiometric ratio is 110% to 2000%. A more preferable range of the increased stoichiometric ratio is 150% to 1500%. The most preferred range of the increased stoichiometric ratio is 200% to 1000%.

The atmospheric conditions in the purification zone 12 are further enhanced by the optional injection of additional purge gas into the purification zone 12 in a manner that does not increase the gas circulation from the fusing zone 11 to the purification zone 12 . For example, additional oxygen may be injected from the at least one purge gas injector 55-58 located at the front wall 23 or at the side wall 22 near the front wall 23. The preferred embodiment differs from the injectors 55 and 56 from the front wall 23 with appropriate momentum to reduce the furnace gas circulation from the fusing zone 11, either with the purge gas injectors 55 and 56 injected together, Purge gas is injected. Preferably, the total momentum of the purge gas injected from each injector 55 and 56 is less than the fuel and air injected from the port 6. The purge gas is preferably air or an oxidizing agent containing 21 to 100% by volume of O ₂ . More preferably, the oxygen concentration of the oxidant is 33 to 100% by volume, and most preferably the oxygen concentration of the oxidant is 85 to 100% by volume. The gas flow rate and composition injected from the purge gas injectors 55 and 56 may be different from each other and may affect the temperature and O ₂ concentration profile in the purification zone 12.

When practicing the present invention with optional purge gas or oxidant injection from injectors 32 and 33, the average excess amount of oxygen in the flue gas exiting the regenerator port will increase. The injection of unheated oxidizer, especially air, increases the heat load of the furnace. In order to maintain or improve the energy efficiency of the furnace and to minimize NOx emissions, the oxygen concentration in the flue gas discharged from each regenerator port is optimized to an optimum value, typically about 1-6 vol%, more typically The fuel and combustion air flow rates of each regenerator port are preferably adjusted to be about 1-3 vol.%. Most of the gas injected into the purification zone is discharged from the regenerator port adjacent to the purification zone so that the fuel and combustion air flow rates of the two to three regenerator ports are adjusted such that the oxygen concentration in the flue gas discharged from each regenerator port is at an optimum value .

However, when producing highly oxidized glass, such as plate glass for solar panel applications, it is desirable to have a high O 2 content in the upper region of the bubbler when the bubble generator is installed in the melting zone, ₂ concentration in the atmosphere. In a typical six-port float glass furnace, a spring zone is located between the port (3) and the port (6) in the melting zone. In this case, it is desirable to increase the stoichiometric ratio of the port 4-6 to a normal excess amount of air level or to 110% to 120% to increase the O ₂ concentration over the port 4-6 region Do. A further increase in the O ₂ concentration near the spring zone is achieved by closing the firing port 6 and expanding the high O ₂ atmosphere of the purification zone to the port 5 line. Optionally, both the port 6 and the port 5, even including the port 4, can be closed. When such a port is closed to increase the O ₂ concentration in the atmosphere near the spring zone, the fuel inflow amount of the remaining ports and the amount of fuel injected from the injectors 32 and 33 optionally increases to maintain the proper furnace temperature profile .

Claims (17)

A glass melting furnace comprising a glass melting chamber defined by opposed sidewalls, a back wall, a roof, and a front wall,
(A) by the heat from the two or more pairs of opposing regenerator ports in the sidewall of the melting zone and the heat provided to the melting zone on the bath by the combustion of the preheated oxidant, Melting the glass melting material in a melting zone of the glass melting chamber to establish a bath of molten glass manufacturing material wherein the combustion forms an atmosphere comprising combustion products in the melting zone of the vessel, ≪ / RTI >
(B) the molten glass manufacturing material passes from the melting zone of the glass melting chamber to the purification zone, and through the purification zone, out of the glass melting chamber through the port at the front wall,
(C) injecting at least one gaseous stream or atomizing fluid stream of fuel and at least one oxidant stream into a refinery zone on top of the molten glass manufacturing material and combusting the fuel and oxidant in the refinery zone, The average oxygen concentration in the atmosphere near the surface of the bath increases by 1 to 60% by volume,
(D) the fuel and combustion air flow rates of each of the regenerator ports are adjusted such that the oxygen concentration in the flue gas discharged from each of the regenerator ports located between the spring zone and the refinery zone is between 2 and 10% by volume
≪ / RTI > 2. The process of claim 1, wherein said at least one oxidant stream injected in step (C) comprises between 21% and 100% by volume of oxygen. 2. The method of claim 1, wherein said at least one oxidant stream injected in step (C) comprises between 35% and 100% by volume of oxygen and said fuel is between 110% and 2000% (C). ≪ / RTI > 4. The method of claim 3, wherein the stoichiometric ratio of the at least one oxidant stream injected at step (C) and the fuel is from 150% to 1500%. 4. The method of claim 3, wherein the stoichiometric ratio of the fuel and the at least one oxidant stream injected in step (C) is 200% to 1000%. The method of claim 1, further comprising bubbling gas from the bottom of the melting zone into molten glass in the melting zone. The method of claim 1, wherein (E) the gas stream flows through the port in the front wall or through one or more separate gas injection ports in the front wall toward the melting zone on top of the molten glass- ≪ / RTI > 8. The method of claim 7, wherein the molten glass manufacturing material flows from the purification zone to the conditioning zone, cooling air is supplied to the conditioning zone to cool the molten glass manufacturing material in the conditioning zone, Wherein the gas stream flows from the conditioning zone to the purification zone and into the purification zone. The method of claim 1, wherein the oxygen concentration in the atmosphere near the bath surface in the purification zone is higher than the oxygen concentration in the atmosphere near the bath surface in the melting zone. The method of claim 1, wherein the average oxygen concentration in the atmosphere in the vicinity of the bath surface in the purification zone is from 2 to 60% by volume. The method of claim 1, wherein the average oxygen concentration in the atmosphere near the bath surface in the purification zone is increased by 1 to 60% by volume. The method according to claim 1, wherein the redox ratio represented by the ratio of ferrous to ferric iron in the glass produced from the glass melting furnace is reduced by 0.01 to 0.20. The method of claim 1, wherein preheated oxidant for combustion is provided in a molten zone above the vessel from 2 to 10 pairs of regenerator ports on the side of the glass melting chamber. 8. The process of claim 7, wherein the gas stream flowing into the purification zone in accordance with step (E) is air. 8. The process of claim 7, wherein said gaseous stream flowing into said purification zone according to step (E) comprises between 21% and 100% by volume of oxygen. 3. The process of claim 2, wherein the gas stream flowing into the purification zone in accordance with step (E) comprises between 50 vol% and 100 vol% oxygen. The method according to claim 1, wherein the glass melting furnace produces an oxidized sheet glass.

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