REFINING OF SUBMERGED COMBUSTION GLASS

Abstract

A method for refining low-density submerged combustion glass is described. The method involves introducing unrefined molten glass (18) produced in a submerged combustion melter (10) into a refining chamber (78) of a downstream refining tank (12). Additive particles (26) are also introduced into the refining chamber (78) to release one or more refining agents (142) into the molten glass bath (22) contained within the chamber (78) to accelerate the removal of bubbles from the molten glass bath (22). Refining the molten glass bath (22) assisted by one or more refining agents (142) allows the refined glass (24) to be discharged from the refining tank (12) with fewer bubbles and a higher density than that of the unrefined molten glass (18) introduced into the refining tank (12).Also described are additive particles (26) that include a physical mixture of a reactive glass material (140) and refining agent(s) (142).

Description

BRIEF DESCRIPTION OF THE INVENTION This disclosure describes a method for refining molten glass discharged from a submerged combustion melter along with additive particles that can be used to support the bubble removal process. The described method involves introducing additive particles, comprising a defined concentration of one or more refining agents, into a molten glass bath contained in a refining tank that receives unrefined molten glass discharged from an upstream submerged combustion melter. The additive particles comprise a physical mixture of a reactive glass material and one or more refining agents.This ensures that the delivery of additive particles to the molten glass bath can supply a precise amount of the refining agent(s) to the glass bath without altering the bath's glass chemistry. This is especially important because standard material feeding equipment is generally not capable of accurately measuring the single, small amount of refining agent(s) required for effective glass clarification. Therefore, the additive particles serve as a carrier for the refining agent(s). To this end, the amount of refining agent(s) added to the molten glass bath in the refining tank can be precisely controlled by controlling the quantity of additive particles introduced into the refining tank. This disclosure describes several aspects that can be implemented separately or in combination to obtain fine foamed molten glass received from a submerged combustion melter. According to one embodiment of this disclosure, a method for refining low-density submerged combustion glass involves several steps. One step of the method includes providing a refining tank downstream of a submerged combustion melter. The refining tank has a shell that defines a refining chamber and contains a molten glass bath within the refining chamber. The shell further defines each of a glass inlet, a glass outlet, and an auxiliary access passage. Within the refining chamber, the molten glass bath flows in a one-way flow direction from the glass inlet to the glass outlet.Another step in the method involves introducing unrefined molten glass produced in the submerged combustion melter into the refining chamber of the refining tank through the glass inlet. The unrefined molten glass has a certain percentage by volume of gas bubbles and a certain density, and upon being introduced into the refining chamber, it mixes with the molten glass bath. A further step in the method involves introducing additive particles into the refining chamber of the refining tank through the auxiliary access passage. The additive particles comprise a reactive glass material and one or more refining agents. The one or more refining agents are released into the molten glass bath after the additive particles are consumed, thereby accelerating the removal of gas bubbles from the molten glass bath.Furthermore, another stage of the method involves discharging refined molten glass from the glass outlet of the refining tank. The refined molten glass has a lower percentage by volume of gas bubbles than the unrefined molten glass and also has a higher density than the unrefined molten glass. According to another aspect of this disclosure, a low-density submerged combustion glass refining method also includes several steps. One step of the method involves producing unrefined soda-lime-silica glass in a submerged combustion melter. The soda-lime-silica glass has a glass composition that includes 60 wt% to 80 wt% SiO2, 8 wt% to 18 wt% Na2O, and 5 wt% to 15 wt% CaO. Another step of the method involves introducing unrefined soda-lime-silica glass into a refining tank located downstream of the submerged combustion melter. The refining tank has a shell containing a molten glass bath composed of soda-lime-silica glass, into which the unrefined soda-lime-silica glass introduced into the refining tank is combined. The molten glass bath flows in one flow direction within the refining chamber towards a glass outlet in the refining tank.Another step in the method involves introducing additive particles into the refining chamber of the refining tank separately from the unrefined molten glass. The additive particles comprise a reactive glass material and one or more refining agents. The refining agents are released into the molten glass bath contained in the refining chamber after the additive particles are consumed, thereby accelerating the removal of trapped gas bubbles from the molten glass bath. A further step in the method involves discharging refined molten glass from the glass outlet of the refining tank. The refined molten glass has a lower percentage by volume of gas bubbles than the unrefined molten glass and a higher density than the unrefined molten glass. According to another aspect of this disclosure, an additive particle is defined for introduction into a molten glass bath contained in the refining chamber of a refining tank located downstream of a submerged combustion melter. The additive particle comprises a physically compacted, homogeneous mixture consisting of a glass reactant / reactive material and one or more refining agents. The one or more refining agents have a concentration within the additive particle ranging from 1% to 30% by weight, based on the total weight of the additive particle. Furthermore, the additive particle has a particle size defined by its largest dimension, ranging from 2 mm to 30 mm. BRIEF DESCRIPTION OF THE DRAWINGS The disclosure, along with its objects, features, advantages, and additional aspects, will be best understood from the following description, the accompanying claims, and the accompanying drawings, in which: FIG. 1 is a raised cross-sectional representation of a submerged combustion melter and a portion of a refining tank located downstream of the submerged combustion melter, wherein the refining tank is configured to receive molten glass discharged from the submerged combustion melter according to an embodiment of the present disclosure; FIG. 2 is a raised cross-sectional representation of the refining tank illustrated in FIG. 1 showing the introduction of additive particles into the molten glass bath contained within a refining chamber of the refining tank; and FIG. 3 is a cross-sectional plan view of the refining tank shown in FIG. 2 taken along section line 3-3; FIG. 4 is a plan view of the roof of the refining tank illustrated in FIG. 2 showing the auxiliary access passage through which additive particles containing one or more refining agents are delivered to the refining tank; FIG. 5 is a representative illustration of an additive particle including one or more refining agents dispersed within a glass reactant material according to an embodiment of the present disclosure; and FIG. 6 is a schematic flow diagram of a process for forming glass containers from refined molten glass discharged from the refining tank according to an embodiment of the present disclosure. DETAILED DESCRIPTION A portion of an overall glass manufacturing operation is shown in FIG. 1, which includes a representative submerged combustion melter (SC) 10 and a refining tank 12 located downstream of the melter 10 SC for the various aspects of this disclosure. A glass feed material 14 formulated to melt and react to produce a particular glass chemistry is introduced into the melter SC 10. The glass feed material 14 melts and reacts within the melter SC 10 and is chemically integrated into molten glass 16 contained within the melter SC 10. A portion of the molten glass 16 is discharged from the melter SC 10 as unrefined molten glass 18. The unrefined molten glass 18 is then delivered to the refining tank 12, either directly or via an intermediate cooling vessel 20.Unrefined molten glass 18 flows through the refining tank 12 as part of a molten glass bath 22, and bubbles are removed to produce refined molten glass 24 that meets the specifications for bubble-free glass and is suitable for further processing into a finished glass article. To aid in the overall refining of the unrefined molten glass 18, one or more chemical refining agents are added to the refining tank 12 by means of additive particles 26 (FIGS. 2 and 5). The additive particles 26 allow for precise and accurate dosing of the refining agent(s) into the refining tank 12 to avoid uncontrolled and unpredictable variations in the amount of refining agent(s) added to the refining tank 12 and the potential consequences of adding too much or too little of the refining agent(s). The SC 10 melter includes a housing 28 having a roof 30, a floor 32, and a vertical wall 34 connecting the roof 30 and the floor 32. The vertical wall 34 further includes a front end wall 34a, a rear end wall 34b that opposes and is separate from the front end wall 34a, and two opposing side walls 34c, 34d that connect the front end wall 34a and the rear end wall 34b. Together, the roof 30, floor 32, and vertical wall 34 define an internal reaction chamber 36 of the melter 10 that contains the molten glass 16 when the melter 10 is in operation. Each of the roof 30, floor 32, and vertical wall 34 can be constructed to withstand the high temperature and corrosive nature of the molten glass 16 or the possible effects of being exposed to the internal environment of the internal reaction chamber 36.For example, each of these structures 30, 32, 34 may be constructed from a refractory material or one or more fluid-cooled panels supporting an internally disposed refractory material having a layer of frozen glass formed in situ in contact with molten glass 16. The housing 28 of the SC 10 melter defines a feed material inlet 38, a molten glass outlet 40, and an exhaust vent 42. Preferably, as best shown in FIG. 1, the feed material inlet 38 is defined in the roof 30 of the housing 28 near the front wall 34a, and the molten glass outlet 40 is defined in the rear wall 34b of the housing 28 above the floor 32, although other locations for the feed material inlet 38 and the molten glass outlet 40 are certainly possible. The feed material inlet 38 provides an entrance to the inner reaction chamber 36 for the delivery of the glass feed material 14. In fact, a batch feeder 44 that is configured to introduce a measured quantity of the glass feed material 14 into the inner reaction chamber 36 can be coupled to the housing 28.And although many designs are possible, the batch feeder 44 may, for example, include a rotating screw (not shown) rotating inside a feed tube 46 of a slightly larger diameter that communicates with the feed material inlet 38 to deliver the glass feed material 14 from a feed hopper to the inner reaction chamber 36 at a controlled flow rate / flow rate(a). The molten glass outlet 40 provides an outlet from the inner reaction chamber 36 for discharging the unrefined molten glass 18 from the melter SC 10. The unrefined molten glass 18 can, as shown, be fed directly into the stabilization / cooling vessel 20, if desired. The stabilization vessel 20 includes a housing 46 that defines a holding compartment 48. The holding compartment 48 receives the unrefined molten glass 18 discharged from the inner reaction chamber 36 of the melter SC 10 through the molten glass outlet 40 and holds a volume 50 of the unrefined molten glass 18. One or more impact or non-impact burners 52 can be mounted in the housing 46 of the stabilization vessel 20 to heat the volume 50 of unrefined molten glass and / or suppress or destroy any foam that may accumulate on top of the volume 50 of unrefined molten glass.A constant or intermittent flow 54 of unrefined molten glass can be delivered from the volume 50 of unrefined molten glass held in the holding compartment 48 and outside the cooling vessel 20 by a nozzle 56 attached to the housing 46. The nozzle 56 may have a reciprocating plunger 58 that can be operated to dispense the flow 54 of unrefined molten glass in a controllable manner through an orifice plate 60 so that the downstream refining tank 12 receives a controlled input of the unrefined molten glass. Of course, in other embodiments, the stabilizing vessel 20 can be omitted and the unrefined molten glass 18 discharged from the inner reaction chamber 36 of the SC 10 melter can be poured or otherwise introduced directly into the refining tank 12. The exhaust vent 42 is preferably defined in the roof 30 of the housing 28 between the front end wall 34a and the rear end wall 34b, downstream of the feed inlet 38. An exhaust duct 62 communicates with the exhaust vent 42 and is configured to remove gaseous compounds from the inner reaction chamber 36. The gaseous compounds removed through the exhaust duct 62 can be treated, recycled, or otherwise disposed of from the melter SC 10 as required. To help prevent or at least minimize the loss of some of the glass feed material 14 through the exhaust vent 42 as unintentional waste material, a partition wall 64, dependent on the roof 30 of the housing 28, can be positioned between the feed inlet 38 and the exhaust vent 42.The partition wall 64 may include a lower free end 66 that is submerged within the molten glass mass 16, as illustrated, or it may be placed near, but above, the molten glass mass 16. The partition wall 64 may be constructed similarly to the ceiling 30, floor 32, and surrounding vertical wall 34, but it does not necessarily have to be constructed that way. The SC 10 melter includes one or more submerged burners 68. Each of the one or more submerged burners 68 is mounted in a defined port 70 in the floor 32 (as shown) and / or the surrounding vertical wall 34 in a location submerged by the molten glass 16. The submerged burner or burners 68 forcefully inject a combustible mixture G of a fuel and an oxidizer into the molten glass 16 through an outlet nozzle 72. The fuel can be methane or propane, and the oxidizer can be pure oxygen (>99% O2 by volume), air, or any oxygen-rich gas (>80% O2 by volume). When injected into the molten glass mass 16, the combustible gas mixture G immediately self-ignites to produce combustion products 74, namely CO2, CO, H2O, and any unburned fuel, oxygen and / or other gaseous compounds, such as nitrogen, which are discharged into and through the molten glass mass 16.Anywhere from five to thirty submerged burners 68 are typically installed in the SC 10 melter, although certainly more or fewer burners 68 can be employed depending on the size and melting capacity of the melter 10. In terms of supplying the submerged burner(s) 68 with the fuel gas mixture G, each of the burners 68 can be seamlessly coupled to a fuel manifold and an oxidizer manifold by means of a flow conduit that is equipped with sensors and valves to allow precise control of the fuel and oxidizer flow rates to the burner(s) 68 in the correct ratio. During operation of the SC 10 melter, each of the one or more submerged burners 68 individually discharges combustion products 74 directly into and through the molten glass 16. The molten glass 16 is a volume of molten glass that often weighs between 1 US tonne (1 US tonne = 2000 lbm) and 100 US tonnes and is generally maintained at a constant volume during steady-state operation of the SC 10 melter. As the combustion gases 74 are pushed into and through the molten glass 16, creating complex flow patterns and severe turbulence, the molten glass 16 is vigorously agitated and experiences rapid heat transfer and intense shear forces.The combustion products 74 eventually escape from the molten glass mass 16 and are removed from the inner reaction chamber 36 through the exhaust vent 42 along with any other gaseous compounds that may volatilize out of the molten glass mass 16. In addition, under certain circumstances, one or more non-submerged burners (not shown) may be mounted on the ceiling 30 and / or the surrounding vertical wall 34 in a location above the molten glass 16 to provide heat to the molten glass 16, either directly by flame impact or indirectly through radiant heat transfer, and also to facilitate the suppression and / or destruction of foam. While one or more submerged burners 68 are heated in the molten glass 16, the glass feed material 14 is introduced in a controllable manner into the inner reaction chamber 36 through the feed material inlet 38. Unlike the operation of a conventional Siemens-style continuous melting furnace, the glass feed material 14 does not form a batch blanket resting on top of the molten glass 16; rather, the glass feed material 14 is rapidly dissolved and consumed by the turbulent molten glass 16. The vigorous stirring and shearing forces generated by the submerged burner or burners subject the glass feed material 14 to intense heat transfer and rapid particle dissolution throughout the molten glass 16.This causes the glass feed material 14 to mix, react, and chemically integrate into the molten glass 16 relatively quickly. However, the agitation and mixing of the molten glass 16 by the direct discharge of combustion products 74 also promotes bubble formation within the molten glass 16. Consequently, the molten glass 16 is foamy in nature and contains a homogeneous distribution of approximately 30% to 60% by volume of entrained gas bubbles. The trapped gas bubbles result in a relatively low density of the molten glass 16, typically between 0.75 g / cm³ and 1.5 g / cm³, or more narrowly from 0.99 g / cm³ to 1.3 g / cm³, for soda-lime-silica glass, compared to a Siemens-style continuous melting furnace.The gas bubbles trapped within the molten glass mass 16 vary in size and contain any of several gases, including CO2, H2O (vapor), SO2, N2, CH4, H2S, CO, O2 and volatile organic compounds (VOCs). The glass feed material 14 introduced into the inner reaction chamber 36 is formulated to produce molten glass within the molten glass mass 16 that has the desired final glass chemistry. Soda-lime-silica glass, for example, is widely used to manufacture flat glass articles, such as windows, hollow glass articles including containers such as bottles and flasks, as well as tableware and other specialty glass articles. Soda-lime-silica glass comprises a spatially cross-linked, disordered ternary oxide network of Na₂O-CaO-SiO₂. The silica component (SiO₂) is the largest oxide by weight and constitutes the main network-forming material of soda-lime glass.The Na₂O component acts as a fluxing agent, lowering the melting, softening, and glass transition temperatures of the glass compared to pure silica glass. The CaO component acts as a stabilizer, improving certain physical and chemical properties of the glass, including its hardness and chemical resistance. The inclusion of Na₂O and CaO in the chemistry of soda-lime-silica glass makes the commercial manufacture of glass articles more practical and less energy-intensive than with pure silica glass, while still providing acceptable glass properties. Soda-lime-silica glass, generally and based on the total weight of the glass, has a chemical composition that includes 60% to 80% by weight of SiO₂, 8% to 18% by weight of Na₂O, and 5% to 15% by weight of CaO. In addition to SiO2, Na2O and CaO, soda-lime-silica glass may include, if desired, other oxide and non-oxide materials that act as network formers, network modifiers, colorants, bleaching agents, redox agents or other agents that affect the properties of the final glass. Some examples of these additional materials include aluminum oxide (Al2O3), magnesium oxide (MgO), potassium oxide (K2O), carbon, sulfates, nitrates, fluorine, chlorine and / or elemental forms or oxides of one or more of iron, arsenic, antimony, selenium, chromium, barium, manganese, cobalt, nickel, sulfur, vanadium, titanium, lead, copper, niobium, molybdenum, lithium, silver, strontium, cadmium, indium, tin, gold, cerium, praseodymium, neodymium, europium, gadolinium, erbium and uranium.Aluminum oxide is one of the most frequently included materials, typically present in amounts up to 2% by weight based on the total weight of the glass, due to its ability to improve the chemical durability of the glass and reduce the likelihood of devitrification. Regardless of what other oxide and / or non-oxide materials are present in soda-lime glass besides SiO2, Na2O, and CaO, the sum total of these additional materials is preferably 10% by weight or less, or more precisely 5% by weight or less, based on the total weight of the soda-lime-silica glass. When producing soda-lime-silica glass using the SC 10 melter, the glass feed material 14 can be a physical mixture of virgin raw materials and optionally waste glass (i.e., recycled glass) and / or other glass precursors that provide a source of SiO2, Na2O, and CaO in the correct proportions along with any of the other materials listed above and summarized below in Table 1. The virgin raw materials can include corresponding amounts of quartz sand (crystalline SiO2), sodium carbonate (Na2CO3), and limestone (CaCO3) as sources of SiO2, Na2O, and CaO in the glass melt 16, respectively. Other virgin raw materials may also be included in the glass feed material 14 to provide a source of one or more of SiO2, Na2O, CaO and possibly other oxide and / or non-oxide materials depending on the chemistry of the soda-lime-silicon glass being produced.These other virgin raw materials may include feldspar slag, dolomite, and calumite. The glass feed material 14 may even include up to 80% by weight of recovered glass. In addition, the glass feed material may include secondary or secondary raw materials that provide colorants, decolorants, redox agents, and may also provide refining agents if it is desired that such agents be introduced into the molten glass mass 16 to complement the refining agents introduced into the molten glass bath 22 as part of the additive particles 26. Table 1: Composition of soda-lime-silica glass Component Weight % Raw / Unprocessed Material Sources SiO2 60-80 Quartz Sand Na2O 8-18 Soda Ash CaO 5-15 Limestone Al₂O₃ 0-2 Nepheline syenite, feldspar MgO 0-6 Magnesite Li₂O 0-2 Lithium oxide K₂O 0-1.5 Potash 5 Fe₂O₃* 0-0.6 Contaminant Cr₂O₃ 0-0.2 Chromium oxide MnO₂ 0-0.2 Manganese dioxide CO₃O₄ 0-0.1 Cobalt oxide TiO₂ 0-0.8 Titanium oxide / dioxide 10 SO₃ 0-0.2 Slag, salt slag Se 0-0.1 Selenium F 0-0.5 Contaminant *Refers to the total amount of Fe₂O₃ and FeO expressed as Fe₂O₃ 15 ------------------ 1st The unrefined molten glass 18 discharged from the melter SC 10 through the molten glass outlet 40 is extracted from the molten glass 16 and chemically homogenized to the desired final glass chemistry. The unrefined molten glass 16 is directed to the refining tank 12, with or without first being collected in the holding compartment 48 of the stabilizing vessel 20, and eventually to additional downstream equipment for further processing into a glass article. Referring now to FIGS. 1-4, the refining tank 12 includes a housing 76 that defines a refining chamber 78. The housing 76 includes a roof 80, a floor 82, and a vertical wall 84 connecting the roof 80 and the floor 82.The vertical wall 84, more specifically, includes an inlet end wall 84a, an outlet end wall 84b separated from the inlet end wall 84a in a flow direction F of the flowing molten glass bath 22, and two opposing side walls 84c, 84d connecting the inlet end wall 84a and the outlet end wall 84b. A floating foam layer 86 may form in the molten glass bath 22. The terms refining and fine, as used in connection with the refining tank 12 and its operation, should be interpreted broadly to encompass all types of bubble removal mechanisms, including thermal management of the molten glass bath 22 and by reactions of refining chemical agent(s) within the glass bath 22. The refining tank 12 housing 76 defines a glass inlet 88, a glass outlet 90, and an auxiliary access passage 92 through which additive particles 26 are introduced into the refining chamber 78 for consumption by the molten glass bath 22. The glass inlet 88 can be defined in the roof 80 of the housing 76 near the inlet end wall 84a, as shown, for example, in FIGS. 1-2 and 4, or it can be defined on the inlet terminal wall 84a above or below a surface of the molten glass bath 22. The glass inlet 88 provides an inlet to the refining chamber 78 for the introduction of the unrefined molten glass 18, 54 discharged from the melter SC 10 either directly or via the cooling vessel 20. The unrefined molten glass 18 can be piped or poured into the refining chamber 78 through the glass inlet 88.In that regard, the molten glass outlet 40 of the SC 10 melter and the glass inlet 88 of the refining tank 12 may be mechanically connected by a continuous flow conduit, or, as shown here, the molten glass outlet 40 and the glass inlet 88 may be mechanically disconnected but in flow communication with each other, since a completely closed conduit having a contained flow path does not extend completely from the spout 56 of the stabilizing vessel 20 to the housing 76 of the refining tank 12. The glass outlet 90 may be defined in the wall of the outlet end 84b of the housing 76 adjacent to the floor 82, as shown, for example, in FIG. 2, or it may be defined in the floor 82 near the wall of the outlet end 84b. The glass outlet 90 provides an outlet from the refining chamber 78 for the discharge of the refined molten glass 24 (FIG. 2) out of the refining tank 12 for further processing. For example, as part of the global production of glass containers, the refined molten glass 24 discharged from the refining tank 12 can be transferred to a spout 94 attached to the refining tank 12. The spout 94 collects the refined molten glass 24 into a spout bowl 96 and includes at least one reciprocating plunger 98 that moves alternately / reciprocally to control the flow of the refined molten glass 24 through an orifice plate 100 to form streams or channels (not shown) of the refined molten glass.The streams or channels of the refined molten glass can be cut into molten glass drops of a predetermined weight that can then be formed into glass containers as will be described in more detail below. Positioned between the glass inlet 88 and the glass outlet 90 within the refining chamber 78, there may be one or more partition walls 102 extending downwards from the ceiling 80 to the floor 82 to define, together with the corresponding portions of the floor 82 and the side walls 84c, 84d of the vertical wall 84, a submerged passage 104. If more than one partition wall 102 is present, the walls 102 are placed in series and separated in the flow direction F of the molten glass bath 22.Herein, three dividing walls are depicted between the inlet end wall 84a and the outlet end wall 84b with respect to the flow direction F of the molten glass bath 22: (1) a first dividing wall 102a providing a first submerged passage 104a; (2) a second dividing wall 102b providing a second submerged passage 104b; and (3) a third dividing wall 102c providing a third submerged passage 104c; however, it is understood that the number of dividing walls 102 could vary, so that more or fewer than three dividing walls 102 could be used. The dividing wall(s) 102 are preferably constructed from heat- and corrosion-resistant materials, many of which are commercially available, including a refractory material such as bonded AZS (with 20 wt% ZrO). Each of the partition walls 102 includes a front face 106, a back face 108, and a free edge 110 that defines a wall thickness 102 between the front and back faces 106, 108. These features of the three partition walls 102a, 102b, 102c shown in FIGS. 2-4 are identified by their respective designations a, b, and c. The freeboard 110 of each partition wall 102 is immersed in the molten glass bath 22 and is separated from the floor 82 of the shell 76 by a distance that varies from 2 inches to 10 inches from the center plane 112 of the wall 102. The magnitude of the distance separating the freeboard 110 of the wall 102 and the floor 82 affects the cross-sectional area of ​​the submerged passage 104 and can therefore influence the flow path and flow velocity of the molten glass bath 22 through the passage 104 and into the refining chamber 78.Furthermore, it has been determined that a smaller distance between the free edge 110 of the partition wall 102 and the floor 82 results in a better distribution of the refining agents carried by the additive particles 26 along the depth of the molten glass bath 22 downstream of the partition wall 102. As shown in this embodiment, the three partition walls 102a, 102b, and 102c divide the finishing chamber 78 into four sequential zones. Located between the inlet end wall 84a and the first partition wall 102a is a glass receiving zone 78a. Located between the first partition wall 102a and the second partition wall 102b is an upstream finishing zone 78b, and located between the second partition wall 102b and the third partition wall 102c is a downstream finishing zone 78c. Finally, between the third partition wall 102c and the outlet end wall 84b is a glass delivery zone 78d. And although the sizes of the various zones 78a, 78b, 78c, 78d may vary, the first dividing wall 102a is preferably placed at a distance d1 (FIG.3) from the inlet end wall 84a, the distance d1 being measured from an inner surface 114 of the inlet end wall 84a to the center plane 112a of the first partition wall 102a, which varies from 20% to 45% of a length L of the finishing chamber 78. Likewise, the second partition wall 102b and the third partition wall 102c are preferably placed at a distance d2, d3 from the inlet end wall 84a (measured the same as the first partition wall 102a) which varies from 35% to 60% and from 70% to 90%, respectively, of the length L of the finishing chamber 78. The length L of the finishing chamber 78, as used herein, is defined as the distance from the inner surface 114 of the inlet end wall 84a (starting at the intersection between the inlet end wall 84a and floor 82) and extending at the same elevation to an end 116 of floor 82 on the exit end wall 84b. The refining tank 12 may include one or more optional stirrers 118 arranged within the glass receiving zone 78a of the refining chamber 78 to stir the molten glass bath 22 and mix the additive particles 26 into the molten glass bath 22. Anywhere from one to five, and more preferably from one to three, stirrers 118 may be arranged in this zone 78a. The stirrers 118 may be of any suitable construction. For example, as shown here in FIG. 2, each of the agitators 118 can be a screw blade agitator comprising a rotating shaft 120 and a helical blade 122 wound helically around an outside of the rotating shaft 120. The rotating shaft 120 extends downwards from the roof 80 of the housing 76 so that the helical blade 122 is totally or partially immersed in the molten glass bath 22.The rotating shaft 120 can be driven by any conventional motor (not shown) and, when rotated, spins the helical blade 122 to induce an axial flow pattern in the molten glass bath 22 in the surrounding vicinity of the blade 122. Of course, other agitators besides the screw blade agitator can also be employed, including, for example, agitators that incorporate a rotating blade / paddle similar to that used in the screw blade agitator but with a propeller, impeller, or turbine blade instead of a helical blade. The upstream refining zone 78b, the downstream refining zone 78c, and the glass delivery zone 78d are preferably free of mechanical agitators. In fact, regardless of whether there are more or fewer than three dividing walls 120, the refining tank 12 can be devoid of agitators downstream of the glass receiving zone 78a. The refining tank 12 may also include one or more heat-emitting devices 124 mounted on the housing 76 above the molten glass bath 22 in each of the zones 78a, 78b, 78c, 78d of the refining chamber 78. The heat-emitting devices 124 may be submerged electrode burners and / or boosters. Preferably, as shown here in FIG. 2, each of the glass receiving zone 78a, the upstream refining zone 78b, the downstream refining zone 78c, and the glass delivery zone 78d includes one or more burners mounted on the ceiling 80 or the opposite side walls 84c, 84d (represented here) at a location above the surface of the molten glass bath 22.These burners can be impact burners, whose combustion products are directed into and make contact with the molten glass bath 22, or they can be non-impact burners, whose flames do not make direct contact with the molten glass bath but nevertheless radiantly transfer heat to it, as is the case with conventional ceiling-mounted flat-flame burners and wall-mounted pencil burners. Heat-emitting devices 124 are operated to control a temperature range Ta, Tb, Te, Td of the molten glass bath 22 within their respective zones 78a, 78b, 78c, 78d, as required to complete the overall refining process. These various temperature ranges may overlap but generally satisfy the relationships Ta<Tb, Tb> Tc> Td and Ta> Td.For example, when the molten glass bath 22 is composed of soda-lime-silica glass, the preferred temperature ranges Ta, Tb, Te, Td of the molten glass bath 22 within each zone 78a, 78b, 78c, 78d of the refining chamber 78 as required to achieve the required glass viscosity in that zone 78a, 78b, 78c, 78d are listed below in Table 2. Table 2: Temperature ranges of the molten glass bath / U 140 1 or Zone Temperature Range (°C) Glass Reception (78a) 1100-1400 Upstream Refining (78b) 1200-1450 Downstream Refining (78c) 1200-1400 Glass Delivery (78d) 1000-1250 The auxiliary access passage 92 is defined in the housing 76 within the glass receiving zone 78a of the refining chamber 78. The auxiliary access passage 92 serves as an inlet to the refining chamber 78, which is separate from the glass inlet 88, for feeding the additive particles 26. In one implementation, the auxiliary access passage 92 can be an elongated slot 126 defined in the roof 80 of the housing 76. The elongated slot 126 can extend vertically through the roof 80 or at an angle through the roof 80, and can also be oriented transverse to the flow direction F of the molten glass bath 22, as best shown in FIG. 4, so that a curtain of additive particles 26 can be evenly distributed through and within the glass bath 22.Alternatively, the auxiliary access passage 92 could also be a plurality of openings grouped together and extending through the ceiling 80 transversely to the flow direction F of the molten glass bath 22 to achieve functionality similar to that of the elongated slot 126. A particle feeder 128 can be used to meter a feed of the additive particles 26 into the refining chamber 78 and, more particularly, the glass receiving zone 78a of the refining chamber 78 through the auxiliary access passage 92. For example, as shown in FIG.2, the particle feeder 128 may include a guide ramp 130 having an outlet 132 in feed communication with the auxiliary access passage 92, as well as an extruder 134 that delivers a controlled amount of the additive particles 26 to the guide ramp 134 by turning a screw 136 within a feed tube 138 of a slightly larger diameter to move the additive particles 26 axially through the feed tube 138 and eventually into the guide ramp 130 at a selected mass flow rate. The additive particles 26 introduced through the auxiliary access passage 92 are shown generically in FIG. 5 and comprise a physical mixture of a glass reactant material 140 and one or more refining agents 142. The glass reactant material 140 serves as a vehicle for the refining agent(s) 142 and is composed of one or more materials that are chemically integrable within the molten glass bath 22. The glass reactant material 140 is chemically integrable because at least 95% by weight, and preferably 100% by weight, of the glass reactant material 140 is composed of one or more materials that, upon introduction into the molten glass bath 22, produce one or more of the glass chemical components already present in the glass bath 22.For example, if the molten glass bath 22 is composed of soda-lime-silica molten glass, at least 95 wt% of the reactive glass material 140 of the additive particles 26 is composed of one or more materials that melt and react within the molten glass bath 22 to produce any of the chemical components listed in Table 1 above, including SiO2, Na2O, CaO, and / or Al2O3. In this respect, the reactive glass material 140 may have the same composition as the glass feed material 14 introduced into the melter SC 10. Alternatively, the reactive glass material 140 may include sodium silicate, or it may include 5 wt% to 90 wt% sodium silicate and 10 wt% to 95 wt% of the glass feed material. One or more chemical refining agents 142 are compounds that can facilitate the removal of bubbles in the molten glass bath 22 by decomposing into refining gases such as oxygen and sulfur oxides, vaporizing, reacting with gases and / or other compounds in the molten glass 22, or by some other mechanism. Several types of suitable refining agents include sulfates such as sodium sulfate (i.e., salt slag) and barium sulfate, carbon, nitrates, carbonates, metal oxides such as MnO2, As2O5, Sb2Os, SnO2, BaO, PbO, Cr2U3, WO3, Li2O, reactive metals such as aluminum, copper, and tin, nitrides, carbides, and water vapor. The concentration of one or more refining agents 142 in the additive particles 26 can range from 1% by weight to 30% by weight or, more narrowly, from 5% by weight to 10% by weight based on the total weight of the additive particles 26, with the reacting glass material 140 preferably constituting the remainder.The refining agent(s) 142 and the glass reactant material 140 are preferably physically homogeneously mixed together within the additive particles 26, although a physically heterogeneous mixture is certainly acceptable. Due to the dynamics of submerged combustion melting and the composition of the gases trapped within the unrefined molten glass 18 as bubbles of various sizes, the refining agent(s) 142 preferably include a reactive oxygen-scavenging metal. Specifically, in a particular implementation, the one or more refining agents 142 may include or consist entirely of aluminum. Aluminum is a functional and practical oxygen-scavenging refining agent because it reacts with H2O and CO2 vapor, both of which are prevalent in the undissolved gases of the unrefined molten glass 18 and, therefore, in the molten glass bath 22, as shown in the following chemical reactions (1) and (2): 2Al +3H2OMAl2O3 + 3H2(1) 4Al + 3CO22Al2O3 + 3C (2) As can be seen, aluminum reacts with H2O vapor to produce Al2O3 and H2 (reaction 1) and reacts with CO2 to produce Al2O3 and carbon (reaction 2). These reactions promote the removal of bubbles in the molten glass bath 22 because H2 diffuses more readily through and out of the molten glass bath 22 than H2O vapor, and the carbon can be absorbed into the glass matrix, form byproducts such as SiC, or slowly oxidize to CO. The reactions of aluminum with H₂O and CO₂ vapor within the molten glass bath 22 also produce Al₂O₃. The in-situ synthesis of Al₂O₃ is not necessarily a concern, as Al₂O₃ is often intentionally included in the glass composition, especially for soda-lime-silica glasses, to improve the durability of the glass network. The ingredients and formulation of the glass feed material 14 can be adjusted, if necessary, to compensate for the aluminum production initiated from Al₂O₃ in the molten glass bath 22 of the refining tank 12. In addition to Al₂O₃ (reactions 1 and 2) and carbon (reaction 2), aluminum can react in the environment of the molten glass bath 22 to produce other compounds as well. In particular, aluminum can react with Fe₂O₃, as shown in chemical reactions (3) and (4) below, to produce FeO and SO₂: 2Al + 3Fe2O3Al2O3 + 6FeO (3) 2Al + 3SO3Al2O3 + 3SO2(4) Again, and depending on the chemistry and desired properties (e.g., color) of the glass, the ingredients and formulation of the glass feed material 14 can be adjusted as needed to account for any changes in color, redox value of the glass (Fe2+ / (Fe2+Fe3+)), or other properties of the molten glass bath 22 as a result of the addition of aluminum in the glass bath 22. The additive particles 26 can be prepared using a conventional compaction technique. This technique involves, first, weighing the glass reactant material 140 and one or more refining agents 142 and mixing the materials 140, 142 together in a ball mill or other device to produce a powder mixture. The resulting powder mixture preferably consists of powder particles having an average particle size between 30 µm and 60 µm. Water is then added to the powder mixture to form a slurry. The slurry is then transferred to a pressing die and compacted at a pressure of, for example, 5,000 lb to 80,000 lb for several seconds to drain the chemically unbound water and produce a compacted green preform of the desired shape.The compacted raw preform is then heated in an annealing oven or other heating device, preferably at a temperature of 35°C to 315°C, until dry. The preform is then separated and screened to capture additive particles 26 of a selected size, such as particles with a larger particle dimension ranging from 5 mm to 30 mm. The additive particles 26, with their known and constant concentration of one or more refining agents 142, can then be packaged or stored until needed for loading into feeder 128 in the refining tank 12. The purpose of refining tank 12 is to remove bubbles (e.g., blisters and seeds) from the molten glass bath 22 so that the refined molten glass 24 discharged from refining tank 12 is suitable for forming glass articles containing no more than a commercially acceptable amount of visual glass imperfections. During the operation of refining tank 12, unrefined molten glass 18, 54 is introduced into the glass receiving zone 78a of the refining chamber 78 through the glass inlet 88. The unrefined molten glass 18, 54 is mixed with the molten glass bath 22 in the glass receiving zone 78a.The molten glass bath 22 is a flowing volume of molten glass and, consequently, over time, the molten glass flows from the glass receiving zone 78a to the upstream refining zone 78b through the first submerged passage 104a, then from the upstream refining zone 78b to the downstream refining zone 78c through the second submerged passage 104b, and finally from the downstream refining zone 78c to the glass delivery zone 78d through the third submerged passage 104c. Each of the zones 78a, 78b, 78c, 78d of the refining chamber 78 contributes to the refining and / or thermal conditioning of the molten glass bath 22 to obtain the refined molten glass 24 that is extracted from the molten glass bath 22 in the glass delivery zone 78d of the refining chamber 78 and discharged from the refining tank 12. The molten glass bath 22 is chemically refined using the refining agent(s) 142 carried by the additive particles 26. As discussed above, the additive particles 26 are introduced into the glass receiving zone 78a upstream of the first partition wall 102a through the auxiliary access passage 92. The additive particles 1 or are engulfed and consumed by the molten glass bath 22, thereby releasing the refining agent(s) 142 into the glass bath 22 as the reacting glass material 140 is assimilated into the glass matrix. The refining agent(s) 142 are dispersed within the molten glass bath 22, a process that is assisted by the axial flow patterns induced by the stirrer(s) 118 if stirrers 118 are employed, and accelerates the removal of trapped gas bubbles when present within the glass bath 22 at a predetermined concentration. The predetermined average concentration of the refining agent(s) 142 in the molten glass bath 22 can be achieved by calculating and adding the amount of additive particles 26 in the glass bath 22 that is needed to achieve the predetermined average concentration given the known concentration of the refining agent(s) 142 in the additive particles and the weight of the glass bath 22.In many cases, and depending on a variety of factors, the predetermined average concentration of the refining agent(s) 142 in the molten glass bath 22 is chosen to range from 5% by weight to 10% by weight based on the total weight of the glass bath 22. In addition to the chemical refining activity, which occurs mainly in the glass receiving zone 78a and the upstream refining zone 78b, as the amount of the refining agent(s) 142 tends to decrease in each of the first three zones 78a, 78b, and 78c of the refining chamber 78 while being depleted in the final zone 78d, the molten glass bath 22 is also thermally refined within the refining chamber 78 to accelerate the ascent of trapped gas bubbles. Such thermal refining involves heating the molten glass bath 22 in the glass receiving zone 78a and the upstream refining zone 78b to decrease the viscosity of the molten glass 22 in those zones 78a and 78b, which in turn increases the rate of ascent of the bubbles out of the glass bath 22 according to Stokes' Law.As explained above, the glass receiving zone 78a and the upstream refining zone 78b of the refining chamber 78 can be maintained at temperatures of 1100°C to 1400°C and 1200°C to 1450°C, respectively, for soda-lime-silica glass. The temperature of the molten glass bath 22 can then be reduced in the downstream refining zone 78c and the glass delivery zone 78d to thermally homogenize the molten glass and achieve a glass viscosity more suitable for downstream forming operations. The downstream refining zone 78c and the glass receiving zone 78d can, as explained above, be maintained at temperatures of 1200°C to 1400°C and 1000°C to 1250°C, respectively, for soda-lime-silica glass. As a result of the refining process that takes place in refining tank 12, the clarified molten glass 24 discharged from refining tank 12 has fewer bubbles as a percentage by volume than the unrefined molten glass 18, 54 fed into refining tank 12. Consequently, the density of the refined molten glass 24 is greater than the density of the unrefined molten glass 18, 54. In particular, and as applicable to soda-lime-silica glass, the unrefined molten glass 18, 54 generally includes a percentage by volume of gas bubbles ranging from 30% to 60% by volume and a density ranging from 0.75 g / cm³ to 1.5 g / cm³, or more narrowly from 0.99 g / cm³ to 1.3 g / cm³, whereas the refined molten glass 24 discharged from refining tank 12 typically has a percentage by volume of gas bubbles below 0.1% by volume, or more narrowly below 0.05% by volume, and a density ranging from 2.3 g / cm3 to 2.5 g / cm3.The refined molten glass 24 coming out of refining tank 12 can be further processed downstream of tank 12. For example, and as will be explained in more detail below, the refined molten glass 24 can have a soda-lime-silica chemistry and be formed into glass containers such as food and beverage bottles and jars, or it can be formed into flat glass products such as windows, or even further, it can be molded into tableware or other glass articles. Glass containers can be formed from the refined molten glass 24 exiting the refining chamber 78 in a forming process 150 as summarized in FIG. 6. In the described process 150, the refined molten glass 24 is passed through nozzle 94 and transformed into a stream or channel (not shown) of fine molten glass in step 152. The streams or channels of fine molten glass are cut at the outlet of nozzle 94 into molten glass drops of a predetermined weight in step 154. Each drop of molten glass is delivered via a droplet delivery system to a blank mold of a single-section container forming machine in step 156. In other alternative processes, however, the molten glass 24 can be flowed directly from the glass outlet 90 of the refining tank 14 into the blank mold to fill the mold with glass.Once in the rough mold, and with its temperature still between 1000°C and 1250°C, the molten glass droplet is pressed or blown in step 158 into a parison or preform that includes a tubular wall. The parison is then transferred from the rough mold to a blow mold of the single-section forming machine in step 160 to give final shape to a vessel. Then, in step 162, once the parison is received in the blow mold, the blow mold is closed and the parison is rapidly blown out into the shape of the final vessel, matching the contour of the mold cavity, using a compressed gas such as compressed air. Of course, other approaches can be implemented to form glass vessels besides pressure-and-blow and blow-and-blow forming techniques, including, for example, compression or other molding techniques. The glass vessel formed within the blow mold has an axially closed base and a circumferential wall. The circumferential wall extends from the axially closed base to a mouth that defines an opening to a defined containment space. 1 or by the axially closed base and circumferential wall. The glass vessel is allowed to cool while in contact with the walls of the blow mold and is then removed from the blow mold and placed on a conveyor or other transport device. At that point, and in an annealing process 170 that follows the forming process 150, the glass vessel is annealed. This may involve first reheating the glass vessel and then cooling it at a controlled rate in an annealing furnace to relax thermally induced constraints and eliminate internal stress points within the vessels.For example, during annealing, the glass vessel may be heated to a temperature above the annealing point of soda-lime-silica glass, which is typically in the range of 500°C to 700°C, followed by slow cooling of the vessel at a rate of 2°C / min to 5°C / min to a temperature below the warping point of soda-lime-silica glass, which is typically in the range of 400°C to 600°C. The glass vessel may then be rapidly cooled after it has reached a temperature below the warping point. Furthermore, any of a variety of coatings may be applied to the surface of the glass vessel before (hot-end coatings) or after annealing (cold-end coatings) for a variety of reasons. Therefore, a method for refining unrefined, foamy, low-density molten glass discharged from a submerged combustion melter has been described, satisfying one or more of the objects and objectives stated above. The resulting fine molten glass can be further processed into glass articles, including, for example, glass containers such as bottles and jugs. The disclosure has been presented together with several illustrative embodiments, and further modifications and variations have been discussed. Other modifications and variations will readily be suggested to those skilled in the art in view of the foregoing discussion. For example, the object of each embodiment is incorporated herein by reference in each of the other embodiments, for convenience. The description purports to encompass all modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. A method for refining low-density submerged combustion glass, the method comprising: providing a refining tank (12) downstream of a submerged combustion melter (10), the refining tank (12) having a shell (76) defining a refining chamber (78) and containing a molten glass bath (22) in the refining chamber (78), the shell (76) further defining each of a glass inlet (88), a glass outlet (90) and an auxiliary access passage (92), and wherein the molten glass bath (22) flows in a flow direction from the glass inlet (88) to the glass outlet (90), the refining tank (12) further including a partition wall (102a) extending downward from a roof (80) of the shell (76) to a floor (82) of the shell (76) to define, together with corresponding portions of the floor (82) and side walls opposites, a submerged passage (104),the partition wall (102a) and an inlet end wall (84a) of the housing (76) located near the glass inlet (88) defining a glass receiving zone (78a) of the refining chamber (78), and wherein each of the glass inlets (88) and the auxiliary access passage (92) are defined in the housing (76) within the glass receiving zone (78a) of the refining chamber (78); introducing unrefined molten glass (18) produced in the submerged combustion melter (10) into the refining chamber (78) of a refining tank (12) through the glass inlet (88), the unrefined molten glass (18) having a percentage by volume of gas bubbles and a density and, upon being introduced into the refining chamber (78), combining with the molten glass bath (22); Introduce additive particles (26) into the tuning chamber (78) of the tuning tank (12) through the auxiliary access passage (92),comprising additive particles (26), a reactive glass material (140), and one or more refining agents (142), the one or more refining agents (142) being released into the molten glass bath (22) after the consumption of the additive particles (26) in the molten glass bath (22) to accelerate the removal of bubbles from the molten glass bath (22); and discharging fine molten glass (24) from the glass outlet (90) of the refining tank (12), the refined molten glass (24) having a volume percentage of gas bubbles that is less than the volume percentage of gas bubbles in the glass (18) and further having a density that is greater than the density of the unrefined molten glass (18).

2. The method set forth in claim [Error! Reference source not found.], wherein the additive particles include a concentration of one or more refining agents ranging from 1% by weight to 30% by weight.

3. The method set forth in claim [Error! Reference source not found.], wherein the one or more refining agents contained in the additive particles include at least one of sulfates, carbon, nitrates, carbonates, metal oxides, reactive metals, nitrides, carbides or water vapor.

4. The method set forth in claim [Error! Reference source not found.], wherein the one or more refining agents contained in the additive particles include at least one of sodium sulfate, barium sulfate, carbon, MnO2, As2O5, Sb2O5, SnO2, BaO, PbO, C^Os, WO3, L2O, aluminum, copper, tin or water vapor.

5. The method set forth in claim [Error! Reference source not found.], wherein the dividing wall (102) includes a free edge (110) that is separated from the floor (82) of the housing (76) by a distance of 2 to 10 inches on a centerline of the dividing wall (102).

6. The method set forth in claim [Error! Reference source not found.], wherein the refining tank further includes one or more heat-emitting devices (124) that heat the molten glass bath within the glass receiving zone of the refining chamber.

7. The method set forth in claim [Error! Reference source not found.]wherein the partition wall defining the glass receiving zone with the inlet end wall of the shell is a first partition wall (102a), and wherein the refining tank further includes a second partition wall (102b) and a third partition wall (102c), the second partition wall being placed downstream of the first partition wall in the flow direction of the molten glass bath to define an upstream refining zone (78b) of the refining chamber together with the first partition wall, and the third partition wall being placed downstream of the second partition wall in the flow direction of the molten glass bath to define a downstream refining zone (78c) of the refining chamber together with the second partition wall and a glass delivery zone (78d) of the refining chamber with an outlet end wall (84b) of the shell located near the glass outlet.

8. The method set forth in claim [Error! Reference source not found.], wherein the second dividing wall extends downwards from the roof of the housing to the floor of the housing to define, together with the corresponding portions of the floor and the opposite side walls, a second submerged passage (104b), and wherein the third dividing wall extends downwards from the roof of the housing to the floor of the housing to define, together with the corresponding portions of the floor and the opposite side walls, a third submerged passage (104c).

9. The method set forth in claim [Error! Reference source not found.], wherein the unrefined molten glass produced by the submerged combustion melter and introduced into the refining tank is composed of soda-lime-silica glass having a glass chemical composition including 60 wt% to 80 wt% SiCh, 8 wt% to 18 wt% Na2O, and 5 wt% to 15 wt% CaO.

10. A method of refining low-density submerged combustion glass, the method comprising: producing unrefined soda-lime-silica glass (18) in a submerged combustion melter (10), the soda-lime-silica glass having a glass chemical composition including 60 wt% to 80 wt% SiCh, 8 wt% to 18 wt% Na2O, and 5 wt% to 15 wt% CaO; introducing the unrefined soda-lime-silica glass (18) into a refining tank (12) located downstream of the submerged combustion melter (10), the refining tank (12) having a housing (76) containing a molten glass bath (22) composed of soda-lime-silica glass in which the unrefined soda-lime-silica glass (18) introduced into the refining tank (12) is combined, the molten glass bath (22) flowing in a flow direction within the refining chamber (78) towards a glass outlet (90) of the refining tank (12);introducing additive particles (26) into the refining chamber (78) of the refining tank (12) separately from the unrefined molten glass (18), the additive particles (26) comprising a reactive glass material (140) and 1 to 30% by weight based on the total weight of the additive particles of one or more refining agents (142), the one or more refining agents (142) being released into the molten glass bath (22) contained in the refining chamber (78) as the additive particles (26) are consumed in the molten glass bath (22) to accelerate the removal of trapped gas bubbles from the molten glass bath (22); and discharging refined molten glass (24) from the glass outlet (90) of the refining tank (12), the refined molten glass (24) having a volume percentage of gas bubbles that is less than a volume percentage of gas bubbles in the glass (18) and furthermore having a density that is greater than the density of the unrefined molten glass (18).; 11. The method set forth in claim [Error! Reference source not found.], wherein the chemical composition of the soda-lime-silica glass further includes up to 2% by weight of Al2O3.

12. The method set forth in claim [Error! Reference source not found.], wherein the one or more refining agents contained in the additive particles include at least one of sodium sulfate, barium sulfate, carbon, MnO2, As2O5, Sb2Os, SnO2, BaO, PbO, C^Ch, WO3, L12O, aluminum, copper, tin or water vapor.

13. The method set forth in claim [Error! Reference source not found.], wherein the refining tank shell includes an inlet end wall (84a) and an outlet end wall (84b) separated from the inlet end wall (84a) in the flow direction of the molten glass bath, the refining tank shell further including a partition wall (102) extending downwards from a roof (80) of the shell to a floor (82) of the shell to define, together with the corresponding portions of the floor and opposite side walls, a submerged passage (104), the partition wall and the inlet end wall of the shell defining a glass receiving zone (78a) of the refining chamber, and wherein each of the unrefined soda-lime-silica glass and additive particles is introduced into the refining chamber of the refining tank within the glass receiving zone.

14. The method set forth in claim [Error! Reference source not found.], wherein the unrefined molten glass has a volume percentage of gas bubbles ranging from 30% to 60% by volume and a density ranging from 0.75 g / cm3 to 1.5 g / cm3, and wherein the refined molten glass discharged from the refining tank has a volume percentage of gas bubbles below 0.05% by volume and a density ranging from 2.3 g / cm3 to 2.5 g / cm3.

15. An additive particle (26) for introduction into a molten glass bath (22) contained in a refining chamber (78) of a refining tank (12) located downstream of a submerged combustion melter (10), the additive particle (26) comprising a physically compacted homogeneous mixture comprising a reactive glass material (140) and one or more refining agents (142), the one or more refining agents (142) having a concentration within the additive particle (26) ranging from 1% by weight to 30% by weight based on the total weight of the additive particle (26), and wherein the additive particle (26) has a particle size defined by its largest dimension ranging from 5 mm to 30 mm.