Patent Application
20240051861
This disclosure relates to a submerged combustion melter as well as a method for melting a batch feedstock material in a submerged combustion melter to produce glass.
A submerged combustion melter (SCM) includes one or more submerged burners that are located below the level of a glass melt contained within the melter. These burners are fed with a fuel, typically a hydrocarbon fuel such as natural gas or propane, and an oxidant such as air, commercially pure oxygen, or an oxygen-enriched gas. The fuel and oxidant are mixed prior to or within the submerged burner and, upon being fired into the glass melt, combust to release combustion products (which include any uncombusted fuel and oxidant) directly into the glass melt. The direct discharge of combustion products into the glass melt produces substantial turbulence in the glass melt, which enhances mixing of the batch feedstock materials fed to the melter and improves heat transfer within the melt, thus accelerating the rate at which the batch feedstock materials are melted and integrated into the melt compared to a conventional glass melting furnace.
Compared to a conventional glass melting furnace—one that relies on radiant heating from overhead burners to heat a relatively calm molten glass bath and melt a blanket of batch feedstock materials fed on top of the glass bath—the necessary residence time of the glass melt in a SCM is reduced due to the more efficient submerged combustion melting process. As such, a SCM can be designed to occupy a smaller footprint that than a conventional glass melting furnace and, due to its reduced size and glass melt capacity, the housing of the SCM can be fluid cooled. Because the housing of the SCM can be fluid cooled, the SCM is able to be repeatedly shut down and restarted since thermal shock and related damage to any refractory materials that may line the SCM housing can be avoided. While there are many benefits to melting glass in a SCM, there are also plenty of challenges. One particular challenge associated with glass melting in a SCM is that the combustion of a hydrocarbon fuel and an oxidant, and the direct discharge of the resultant combustion products into the glass melt, tends to generate NOX, SOX, and CO2 that exits the SCM as part of a flue gas. These gases are generated during the combustion reaction itself and/or through reactions that proceed during intimate contact between the combustion products and the glass melt. The NOX, SOX, and CO2 emissions included in the SCM flue gas, in turn, may need to be abated through an exhaust treatment process and/or the SCM may have to be operated in a less-than-desired way to reduce NOX, SOX, and CO2 emissions to acceptable levels.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other. According to one embodiment of the present disclosure, a method of making glass includes several steps. One step of the method involves discharging combustion products from each of one or more submerged combustion burners directly into a glass melt contained within a submerged combustion melter. The combustion products result from the combustion of hydrogen gas and an oxidant gas. Another step of the method involves exhausting a flue gas flow from the submerged combustion melter. Yet another step of the method involves delivering a preheater gas flow to a batch feedstock material preheater to heat batch feedstock material. The preheater gas flow comprises at least the flue gas flow exhausted from the melter, and the batch feedstock material comprises cullet. Another step of the method involves introducing the batch feedstock material into the submerged combustion melter after being heated in the batch feedstock material preheater. Still another step of the method involves removing a condenser gas flow from the batch feedstock material preheater. The condenser gas flow has a temperature lower than a temperature of the preheater gas flow delivered to the batch feedstock material preheater. Yet another step of the method involves condensing the condenser gas flow to form a water condensate. And still another step of the method involves cooling the submerged combustion melter with an inflow of cooling water that includes the water condensate obtained from condensing the condenser gas flow.
According to another embodiment of the present disclosure, a method of making glass includes several steps. One step of the method involves discharging combustion products directly into a glass melt contained within a submerged combustion melter. The combustion products agitate the glass melt and result from the combustion of a mixture of hydrogen gas and an oxidant gas. Another step of the method involves exhausting a flue gas that comprises water vapor from the submerged combustion melter. Still another step of the method involves heating a batch feedstock material with the flue gas. The batch feedstock material comprises at least 40 wt % cullet. Yet another step of the method involves introducing the batch feedstock material into the glass melt contained within the submerged combustion melter. Another step of the method involves condensing the flue gas after the flue gas is used to heat the batch feedstock material to form a water condensate that includes liquid water. And yet another step of the method involves supplying the liquid water to the submerged combustion melter to cool the melter.
According to yet another embodiment of the present disclosure, a glass-melting system is disclosed that includes a submerged combustion melter, a batch feedstock material preheater, a condenser, and a cooling water reservoir. The submerged combustion melter comprises a housing that includes an enclosed shell, which interiorly defines and internal cooling flow path, and further comprises at least one submerged combustion burner configured to introduce a mixture of hydrogen gas and an oxidant gas directly into the melter. Each of a batch inlet and an exhaust outlet is defined through the housing of the submerged combustion melter. The batch feedstock material preheater is in fluid communication with the submerged combustion melter and is configured to heat batch feedstock material with a preheater gas flow that includes flue gas exhausted from the submerged combustion melter through the exhaust outlet. The preheater gas flow exits the batch feedstock material preheater as a condenser gas flow. The condenser is in fluid communication with the batch feedstock material preheater and is configured to condense the condenser gas flow exiting the batch feedstock material preheater into a water condensate. The cooling water reservoir is in fluid communication with the condenser and the submerged combustion melter. The cooling water reservoir is configured to receive the water condensate from the condenser and to deliver an inflow of cooling water to the internal flow path of the enclosed shell of the submerged combustion melter.
The present disclosure relates to a submerged combustion melter that includes one or more submerged combustion burners that combust a mixture of hydrogen gas and an oxidant gas. Here, hydrogen is fed to each of the one or more submerged combustion burners as the fuel rather than a typical hydrocarbon gas, and the oxidant gas includes at least 30 vol % O2 or, more preferably, at least 90 vol % 02 or even at least 99 vol % 02. Ideally, the combustion of hydrogen and the oxidant gas in each of the submerged combustion burners releases water as the predominant emission. The amount of CO2, NOX, and SOX released into the melter flue gas can also be minimized with greater efficacy as each of the volumetric percentage of O2 in the oxidant gas and the cullet content of the batch feedstock material increases (along with using hydrogen gas as the fuel). This is because CO2 is not a byproduct of H2 combustion or the melting of cullet, the impurities that typically generate NOX and SOX emissions are generally not contained in hydrogen gas or cullet, and the amount of NOX and SOX emissions generated when combusting hydrogen gas and the oxidant gas generally decreases with an increasing O2 concentration in the oxidant gas. Additionally, heat from the flue gas released from the melter, which includes water (H2O(v)) as the predominant gaseous emission (and possibly the only gaseous emission), can be recovered to heat all or a portion of the batch feedstock material fed to the melter, or the water vapor in the flue gas exiting the melter can be condensed and delivered to the melter for cooling, or both. In this way, the melter can be a self-source of (i) heat for pre-heating some or all of the batch feedstock material and/or (ii) cooling water for cooling the melter housing. The melter can be included in a glass melting system that takes advantage of these opportunities.
Referring now to
During operation of the glass melting system, a batch feedstock material 22 is introduced into the melter 12 after being heated in the batch feedstock material preheater 14. At the same time, a mixture 24 that comprises hydrogen gas as the fuel and an oxidant gas is introduced or fired directly into a glass melt 26 contained within an interior reaction chamber 28 of the melter 12 through each of one or more submerged combustion burners 30. The combustion reaction between the hydrogen and oxidant gases results in combustion products 32 being discharged directly into and through the glass melt 26 from each of the submerged combustion burners 30, which agitates the glass melt 26 and generates turbulent flow patterns within the melt 26. The agitation of the glass melt 26 quickly disperses the batch feedstock material 22 received therein and improves melting and reaction kinetics by mixing and heating the feedstock material 22 more rapidly compared to conventional glass melting practices. The batch feedstock material 22 eventually melts into molten glass and assimilates into the glass melt 26. An outflow of molten glass 34 is drawn from the interior reaction chamber 28 of the melter 12 and a flow of expended cooling water 36 exits the melter 12. The outflow of molten glass 34 that is pulled from the melter 12 is preferably delivered to downstream equipment before being formed into finished glass articles such as, for example, glass containers
As shown in
The housing 38 defines a batch inlet 52, a molten glass outlet 54, and an exhaust outlet 56, which may be defined through the inlet end wall 46a, the outlet end wall 46b, and the roof 42 of the enclosed shell 40, respectively, but those locations are not mandatory and can be located elsewhere in the housing 38, if desired. For instance, the batch inlet 52 may be defined in the housing 38 below a level 58 of the glass melt 26, as shown in
The one or more submerged combustion burners 30 are mounted in the housing 38 and are submerged by the glass melt 26. The submerged combustion burners 30 are preferably received through the housing 38 and spaced apart along the floor 44 of the enclose shell 40 of the housing 38, although one or even several of the burners 30 may be received through the housing 38 and distributed along the upstanding wall 46 of the shell 40 at a location immersed by the glass melt 26. Each of the one or more submerged combustion burners 30 introduces the mixture 24 of hydrogen gas and an oxidant gas directly into the glass melt 26. The mixture of hydrogen gas and the oxidant gas does not include a hydrocarbon gas and, additionally, the mixture 24 is preferably fed separately to each of the individual burners 30 and then mixed internally within the burners 30. The hydrogen gas supplied to the submerged combustion burner(s) 30 as part of the mixture may include at least 80 vol % H2, although the hydrogen gas in preferred implementations includes at least 95 vol % to 100 vol % H2 with any remainder being commercially acceptable impurities. As for the oxidant gas, it may include at least 30 vol % O2, although the oxidant gas in preferred implementations includes at least 90 vol % O2 or even at least 99 vol % 02 with any remainder being commercially acceptable impurities. Some examples of a suitable oxidant gas include vacuum swing absorption grade commercial oxygen (minimum O2 purity of 90-93 vol %) and cryogenic distillation grade commercial oxygen (minimum O2 purity of 99.5 vol %).
The mixture 24 of hydrogen gas and the oxidant gas autoignites upon exiting its respective burner 30 to discharge combustion products 32 that comprise water vapor into the glass melt 26. Depending on the purities and respective gas flow rates of the hydrogen gas and the oxidant gas, the amount of water vapor included in the combustion products 32 discharged from each of the burners 30 may vary, but typically constitutes at least 50 vol %—or even as much as at least 75 vol % or at least 85 vol %—of the discharged combustion products 32 based on the overall volumetric flow rate of the combustion products 32. For example, the amount of water vapor in the combustion products 32 can be increased by (i) increasing the content of H2 and O2 in the mixture 24 of hydrogen gas and the oxidant gas to help limit the flow of other gases through the burner(s) 30 that do not participate in the combustion reaction and (ii) approaching a stoichiometric gas flow of H2 and O2 to reduce the flow of uncombusted H2/O2 through the burner(s) 30. The discharged combustion products 32 agitate and heat the glass melt 26 so that the batch feedstock material 22, when introduced into the glass melt 26 in the melter 12, is disbanded, mixed, and melted to form molten glass that assimilates into the glass melt 26. Depending on the weight of the glass melt 26, which in some cases may contain between 50 and 200 metric tons of molten glass, the melter 12 may include anywhere from five to forty submerged combustion burners 30.
The batch feedstock material 22 introduced into the submerged combustion melter 12 includes at least 40 wt % cullet. More preferably, however, the batch feedstock material 22 includes at least 60 wt % cullet or, more narrowly, at least 95 wt % cullet or at least 98 wt % cullet, and may even comprise 100 wt % cullet. The remaining portion of the batch feedstock material 22, if any, may be mineral additions to adjust the color and/or the composition of the glass melt 26. These mineral additions may include one or more of colorants, decolorants, and redox agents. Virgin raw materials such as quartz sand, soda ash, and limestone are preferably omitted from the batch feedstock material 22 to keep CO2-producing raw materials out of the melter 12. The batch feedstock material 22 may be formulated to produce any of a variety of glasses, including oxide glasses such as, for example, soda-lime-silica glass having a chemical composition that comprises 60-80 wt % SiO2 (71-74 wt % preferred), 8-18 wt % Na2O (12-15 wt % preferred), and 5-15 wt % CaO (9-13 wt % preferred), along with optional compounds including 0.5-3 wt % Al2O3. To produce soda-lime-silica glass, the cullet included in the batch feedstock material 22 is soda-lime-silica cullet (i.e., pieces of previously formed soda-lime-silica glass). Other types of oxide glasses that may be produced by melting the batch feedstock material 22 besides soda-lime-silica glass include borosilicate glass and an aluminosilicate glass.
The combustion of the hydrogen and oxidant gas mixture 24 and the discharge of the combustion products 32 into and through the glass melt 26 from the submerged combustion burners(s) 30 produces a flue gas within the interior reaction chamber 28. The flue gas includes water vapor and possibly some entrained particulate material including, most notably, batch feedstock material particulates that may be swept up into a head space 74 of the interior reaction chamber 28 above the glass melt 26. The flue gas is exhausted from the melter 12 as a flue gas flow 72. And since the main contributor to the flue gas comprising the flue gas flow 72 is the combustion products 32 discharged from the submerged combustion burner(s) 30, the flue gas flow 72 contains a notable contingent of water vapor—typically at least 40 vol % H2O(v) although, depending on the purity and respective flow rates of the hydrogen and oxidant gases to the burners 30 and the cullet content of the batch feedstock material 22, the flue gas flow 72 may contain a higher water vapor content, such as at least 60 vol % H2O(v) at least 70 vol % H2O(v) at least 80 vol % H2O(v) at least 90 vol % H2O(v) or even at least 95 vol % H2O(v) The flue gas flow 72 is exhausted out of the interior reaction chamber 28 through the exhaust outlet 56 defined in the housing 38 and typically has a temperature of 1150° C. or higher or, more specifically, a temperature of 1200° C. to 1400° C. Because of the high temperature and substantial water content of the flue gas flow 72, the sensible and/or the latent heat of vaporization of the flue gas flow 72 may be recovered and used within the glass melting system 10. Several options for recovering thermal energy from the flue gas flow 72 are described in more detail below.
The sensible heat of the flue gas flow 72 may be transferred to the batch feedstock material 22 in the batch feedstock material preheater 14. Indeed, after exiting the melter 12, the flue gas flow 72 is delivered to the batch feedstock material preheater 14 as all or part of a preheater gas flow 76. In the embodiment shown here, the flue gas flow 72 is directed from the exhaust outlet 56 and into a melter exhaust line 78, and is then combined with a recycled gas flow 80 returning through a gas recirculation line 82 to provide the preheater gas flow 76 within a preheater gas inlet line 84. In this case, each of the flue gas flow 72 and the recycled gas flow 80 constitutes a portion of the preheater gas flow 76. If, however, the recycled gas flow 80 is not combined with the flue gas flow 72 in the manner shown in
The preheater gas flow 76 is introduced into the batch feedstock material preheater 14 through the preheater gas inlet line 84 at a temperature of 300° C. to 1100° C. or, more typically, at a temperature of 600° C. to 800° C. The temperature of the preheater gas flow 76 depends on the volumetric gas flow ratio of the flue gas flow 72 to any other gas flows including, if applicable, the recycled gas flow 80, as well as the temperature(s) of the gas flow(s). The batch feedstock material preheater 14 may be any device capable of transferring sensible heat from the preheater gas flow 76 to the batch feedstock material 22 to raise a temperature of the batch feedstock material 22 prior to the material 22 being introduced into the melter 12. For example, the batch feedstock material preheater 14 may be a direct contact raining bed counterflow preheater—an example of which is shown and described in each of U.S. Pat. Nos. 4,875,919 and 5,125,943—in which the preheater gas flow 76 is delivered into a heating chamber 86 of the preheater 14 through a preheater gas inlet 88 proximate a bottom wall 90 of the preheater 14 and, as a result, flows upwards and through the heating chamber 86. The preheater gas flow 76 eventually exits the preheater 14 through a preheater gas outlet 92 proximate a top wall 94 of the preheater 14 as a condenser gas flow 96. The condenser gas flow 96 then enters a preheater gas outlet line 98 that is connected to the preheater gas outlet 92.
At the same time the preheater gas flow 76 is flowing upwards through the heating chamber 86, the batch feedstock material 22 is introduced into the heating chamber 86 of the preheater 14 through a feed inlet 98 proximate the top wall 94 of the preheater 14 and falls through the heating chamber 86 in direct heat exchange contact with the counterflowing preheater gas flow 76. The preheater 14 may include baffles or other flow deflectors within the heating chamber 86 to deflect the falling batch feedstock material 22 and reroute the upwardly-flowing preheater gas flow 76 to increase the residence time of both the batch feedstock material 22 and the preheater gas flow 76 within the heating chamber 86 to achieve the desired heat exchange. The batch feedstock material 22 exits the batch feedstock material preheater 14 through a feed outlet 100 defined in the bottom wall 90 of the preheater 14 and is heated relative to the temperature of the batch feedstock material 22 entering the preheater 14 through the feed inlet 98. The batch feedstock material 22, for example, may be heated to a temperature of 100° C. to 600° C. or, more preferably to a temperature of 200° C. to 500° C., by the preheater 14 for introduction into the melter 12, and the condenser gas flow 96 leaving the preheater 14 through the preheater gas outlet line 98 may have a reduced temperature of 200° C. to 700° C. or, more narrowly, of 400° C. to 600° C. The batch feedstock material 22 that exits the preheater 14 is carried towards the melter 12 in a charger feed line 102 that is connected to the feed outlet 100.
Once preheated, the batch feedstock material 22 is introduced into the melter 12 through the batch inlet 52 by a feed material charger 104. The feed material charger 104 may be any device that can deliver controlled amounts of the batch feedstock material 22 into the melter 12 for melting. For instance, in one embodiment, the feed material charger 104 includes a hopper 106 that funnels the batch feedstock material 22 delivered from the feed outlet 100 of the batch feedstock material preheater 14 into a feeding tube 108. Housed within the feeding tube 108 is a feeder, such as a rotatable screw or a reciprocating plunger, that is actuatable to controllably meter the batch feedstock material 22 through the feeding tube 108 and into the interior reaction chamber 28 of the melter 12. The batch feedstock material 22 may be introduced into the interior reaction chamber 28 of the melter either above or below the melt level 58 of the glass melt 26. Introducing the batch feedstock material 22 directly into the glass melt 26 below the melt level 58 can help mitigate carryover—i.e., when particles of the batch feedstock material 22 avoid being melted in the glass melt 26 and instead flow directly out of the exhaust outlet 56 as part of the flue gas flow 72—and, thus, possibly lessen or eliminate the need for the particulate separator 16 in the glass melting system 10. One construction of a feed material charger that can feed the batch feedstock material 22 directly into the glass melt 26 is disclosed in U.S. Pub. No. 2020/0156979.
After leaving the batch feedstock material preheater 14, the condenser gas flow 96 may be directed through the particulate separator 16 to recover solid particles that may be entrained in the gas flow 96. Such particulate matter may include batch feed material particulates along with other particulates that may be included in the flue gas flow 72 exiting the melter 12. The particulate separator 16 separates the entrained solid particulate matter from the condenser gas flow 96—recovering over 95 wt % and typically over 99 wt % of all solid particles carried within the condenser gas flow 96—to obtain separated particulates 110. One type of particulate separator that may be used here in the glass making system 10 is a cyclone separator. In a cyclone separator, the condenser gas flow 96 is directed into a separation chamber 112 through a separator gas inlet 114. The separation chamber 112 is constructed to force the condenser gas flow 96 into a spiral vortex, which causes the entrained solid particles to fall downwards through the separation chamber 112 into the separated particulates 110 while the condenser gas flow 96 is pushed upwards and out of the separator 16 through a separator gas outlet 116. Upon exiting the particle separator 16, the condenser gas flow 96 is drawn into a gas condensation line 118 connected to the separator gas outlet 116. A fan 120 may be disposed within the gas condensation line 118 to help pull the condenser gas flow 96 out of the particle separator 16 and the batch feedstock material preheater 14 and to further propel the condenser gas flow 96 through the gas condensation line 118.
The separated particulates 110 recovered from the condenser gas flow 96 exit the separation chamber 112 through a particulate outlet 122 and may be delivered back into the submerged combustion melter 12 either directly or, as shown, through the feed material charger 104. In the embodiment shown here in
A portion of the condenser gas flow 96 passing through the gas condensation line 118 may be diverted into the recirculation line 82 that branches off the gas condensation line 118. The diverted portion of the condenser gas flow 96 directed into the recirculation line 82 constitutes the recycled gas flow 80, which, as described above, may be combined with the flue gas flow 72 to form the preheater gas flow 76. The condenser gas flow 96 is delivered to the condenser 18 where the condenser gas flow 96 is brought into heat exchange communication with a coolant and condensed, thus recovering the latent heat of vaporization of the water vapor included in the gas flow 96. The condenser 18 may be a shell and tube heat exchanger, as shown, that includes a casing 128 that defines a shell space 130 and one or more heat exchange tubes 132 that extend through the shell space 130 between an inlet plenum 134 and an outlet plenum 136. The condenser gas flow 96 delivered to the condenser 18 may be directed through interior flow channels of the heat exchange tubes 132 and a cooling fluid 138 may be directed through the shell space 130 as shown in
The condenser 18 condenses the water vapor included in the condenser gas flow 96 to produce a water condensate 140 that includes liquid water. For example, when operating the condenser 18 as configured in
The water condensate 140 exits the condenser 18 through a condensate outlet 150, which, here, communicates with the outlet plenum 136 of the condenser 18, and the cooling fluid 138 exits the condenser 18 through the fluid cooling outlet 146. The cooling fluid 138 exiting the condenser 18 may be used elsewhere within or outside the glass melting system 10, if needed, as a cooling medium or a heating medium (i.e., hot water). The water condensate 140 is delivered to the cooling water reservoir 20 through a condensate line 152 that connects the condensate outlet 150 with the reservoir 20 to supply a bulk cooling water bath 154 held within the reservoir 20. The cooling water reservoir 20 may be a water basin, a water tower or column, or any other type of vessel that can hold water, and may include a drain valve 156 to help control the volume of the bulk cooling water bath 154. A cooling water delivery line 158 connects a water outlet 160 of the cooling water reservoir 20 with the cooling inlet 62 of the enclosed shell 40 of the housing 38 of the melter 12 so that an inflow of cooling water 162 can be delivered from the cooling water reservoir 20 to the melter 12. A pump 164 may be disposed in the cooling water delivery line 158 to transfer the inflow of cooling water 162 into the melter 12 through the cooling water delivery line 158. And, while not necessarily required, cooling water from an external source may be introduced into the cooling water reservoir 20 to replenish the bulk cooling water bath 154 or to help maintain the bath 154 at a certain volume within the reservoir 20.
When received at the melter 12, the inflow of cooling water 162 is passed through the internal cooling flow path 60 of the shell 40 (
As described above, the glass-melting system 10 is configured so that the flue gas exhausted from the submerged combustion melter 12 through the exhaust outlet 56 can be used to preheat incoming batch feedstock material 22 and, additionally, the water included in the flue gas can be returned to the melter 12 to cool the melter 12. Indeed, after being exhausted form the melter 12, the flue gas is contained in the flue gas flow 72 and then continues to the batch feedstock material preheater 14 as all or part of the preheater gas flow 76. The flue gas traverses the batch feedstock material preheater 14 and then exits the preheater 14 as all or part of the condenser gas flow 96. Next, as all or part of the condenser gas flow 96, the flue gas passes through the particle separator 16 and is delivered to the condenser 18 after a portion of the condenser gas flow 96 is optionally diverted as the recycled gas flow 80. Once at the condenser 18, the water included in the flue gas undergoes a phase change and is condensed from water vapor to liquid water. The liquid water condensed from the condenser gas flow 96 is discharged from the condenser 18 as the water condensate 140 and is eventually supplied back to the submerged combustion melter 12 as cooling water. More specifically, the liquid water is supplied to the internal cooling flow path 60 defined within the enclosed shell 40 of the housing 38 of the melter 12. The liquid water returned to the melter 12 may be all or part of the inflow of cooling water 162 supplied from the bulk cooling water bath 154 maintained within the cooling water reservoir 20, which collects the water condensate 140 that exits the condenser 20. As can be seen, within the glass-melting system 10, water(v) that is exhausted from the exhaust outlet of the melter 12 can be returned to the internal cooling flow path 60 defined in the enclosed shell 40 of the melter housing 38 as cooling water(v) after being used to preheat the batch feedstock material 22.
There thus has been disclosed a glass-melting system and a method of melting glass in a submerged combustion melter. The disclosure has been presented in conjunction with several illustrative embodiments, and additional modifications and variations have been discussed. Other modifications and variations readily will suggest themselves to persons of ordinary skill in the art in view of the foregoing discussion. For example, the subject matter of each of the embodiments is hereby incorporated by reference into each of the other embodiments, for expedience. The disclosure is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.
