Synchronous oxygen-fuel combustion system and method for regenerative glass melting furnace

Abstract

A system and method for synchronous oxy-fuel combustion for a regenerative glass melting furnace, the regenerative glass melting furnace comprising a first group and a second group of regenerative air-fuel burners, a first dual-stage oxy-fuel burner mounted in a first wall and a second dual-stage oxy-fuel burner mounted in a second wall, each oxy-fuel burner having a main oxygen valve for distributing the oxygen flow between main oxygen and staged oxygen, and a staged mode valve for distributing the staged oxygen flow between an upper stage port and a lower stage port of the corresponding burner, and a controller programmed to control the main oxygen valve and the staged mode valve of each of the first and second oxy-fuel burners to adjust the flame characteristics of the first and second oxy-fuel burners according to the operating state of the furnace.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 17 / 073,451, filed on October 19, 2020, and U.S. Application No. 62 / 925,949, filed on October 25, 2019, the entire contents of which are incorporated herein by reference as if fully set forth. Technical Field

[0003] The present application relates to the use of oxyfuel combustion burners in regenerative glass melting furnaces and, in particular, to improving the efficiency of those burners. Background Art

[0004] Zero-port oxy-fuel booster burners have gained wide acceptance for use in float glass furnaces as a valuable means of increasing glass production and / or improving efficiency. However, the effectiveness of booster burners is often limited by the interaction of the flame with the highly turbulent air-fuel flame. In addition, the intensity and direction of these oxy-flames, as well as their air-fuel flame interaction, can vary significantly after each regenerator reversal cycle. These factors can cause negative effects, including charge wall overheating and flame instability, resulting in concentrated heat release near the breast wall and / or flame tilting toward the top.

[0005] Oxyfuel booster burners have been used in air-fired regenerative furnaces for decades, and their benefits are well known. The main benefits include higher furnace efficiency and / or lower fuel consumption, higher productivity, better glass quality and lower NOx. Despite the benefits of oxyfuel booster burners, there are also challenges, such as maintaining a stable, high-brightness flame that can withstand the high levels of turbulence generated in air-fired regenerative glass furnaces. The cyclical nature of the combustion direction in a regenerative furnace produces changing airflow and turbulence patterns, which can cause the booster burner flame to tilt, deflect, and become unstable in other ways. An unstable booster burner flame may cause overheating of the nearby charge wall. In addition, premature flame shortening or extinction may lead to extreme flame conditions, such as, on the one hand, concentrated heat release near the breast wall and / or flame tilting toward the top. This situation usually leads to overheating of the furnace refractory (breast wall / top / charge end wall) and reduces the heat transfer rate between the flame and the glass surface. On the other hand, the combustion space turbulence also interrupts the mixing between the fuel and oxygen, resulting in incomplete combustion. This is particularly true in staged oxy-fuel burners where the mixing of oxygen and fuel is inherently delayed by redirecting a portion of the oxygen above or below the flame, thereby producing a longer, brighter flame. Therefore, the interaction between combustion space turbulence and staged oxy-fuel burners can result in high emissions of carbon monoxide through the furnace flue duct.

[0006] Figure 1 A typical regenerative furnace 10 is schematically depicted having regenerators 12A and 12B on opposite sides of the furnace 10, a charging end 14 for introducing solid glass molten material into the furnace 10, and an outlet end 16 for molten glass to exit the furnace 10 (the direction of glass flow is indicated by the arrow labeled G). Each regenerator 12A, 12B has a set of air-fuel burner ports (six are shown in the depicted embodiment, numbered 1 to 6 from the charging end 14 to the outlet end 16, but a set may include one or more burners). In the depicted operating mode, regenerator 12B is burning (i.e., its air-fuel burners 1 to 6 are operating) while regenerator 12A is exhausting combustion products from the furnace 10. In addition, the oxy-fuel combustion-supporting burners are shown in the "zero port" position (each labeled 0), and both oxy-fuel combustion-supporting burners continue to burn regardless of which regenerator 12A, 12B is burning and which is exhausting. In this mode of operation, potential gas recirculation zones 18 may form in the horizontal (combustion) plane between the port 1 air-fired burner and the port 0 oxy-fuel-assisted burner. These recirculation zones may cause the assisted burner flame to be entrained in the gas flow of the nearest air-fired burner (when firing on the same side), or may alternately obstruct or deflect the gas flow of the oppositely firing assisted burner. This situation can be modeled using the Ansys Fluent computational fluid dynamics (CFD) simulation tool. In the 3D simulation, the size and geometry of a typical air-fired regenerative furnace were replicated based on a production rate of 650 tons per day. Figure 2 and Figure 3 The CFD modeling results are shown separately for the horizontal (combustion) and vertical (charging wall) planes. Figure 2 The oxy-fuel flame (arrow B) is shown bending toward the charge end wall 14 on the exhaust side E of the furnace 10 (and the oxy-fuel flame bending toward the air-fuel flame on the combustion side F of the furnace 10). Figure 3 A potential overheating zone 14A is shown on the charge end wall 14. These results strongly support the above inferences about the detrimental effects of the combustion space flow field on the oxygen-fuel zero-port auxiliary burner opposite the flow field. The main purpose of the system and method described herein is to eliminate these negative effects while maintaining and maximizing the beneficial effects of the auxiliary burner. Summary of the invention

[0007] By understanding the nature of the interaction between the regenerative furnace's circulating air fuel burner operation and the oxy-fuel booster burner flame, the inventors have developed an advanced burner technology that automatically adjusts flame characteristics (particularly length, brightness and momentum) at each regenerative reversal to avoid negative effects while maximizing the performance benefits of oxy-fuel. This development combines advanced control technology with recent dual-stage oxy-fuel flat flame burners. This article describes the method and beneficial results of field implementation of a synchronized oxy-fuel booster burner.

[0008] Aspect 1. A system for synchronous oxygen-fuel combustion of a regenerative glass melting furnace, the regenerative glass melting furnace having a first group of regenerative air-fuel burners and a second group of regenerative air-fuel burners, and a furnace control system, the furnace control system being programmed to control the alternating combustion of the first group of air-fuel burners and the second group of air-fuel burners, so that when the first group of air-fuel burners is burning, the second group of air-fuel burners is storing heat, and when the first group of air-fuel burners is storing heat, the second group of air-fuel burners is burning, the system comprising: a first dual-stage oxygen-fuel burner, installed in a first wall of the furnace and having a main oxygen valve to distribute the oxygen flow between the main oxygen and the staged oxygen, and a staged mode valve to distribute the staged oxygen flow between the upper stage port and the lower stage port; a second dual-stage oxygen-fuel burner , installed in the second wall of the furnace, the second wall is opposite to the first wall, and has a main oxygen valve to distribute the oxygen flow between the main oxygen flow and the staged oxygen flow, and a staged mode valve to distribute the staged oxygen flow between the upper staged oxygen flow to the upper staged port and the lower staged oxygen flow to the lower staged port; and a controller, which is programmed to: receive a signal from the furnace control system as to which group of the first and second groups of air-fuel burners is burning, and which group of the first and second groups of air-fuel burners is storing heat; and in response to the signal from the furnace control system, send a signal to actuate the main oxygen valve and the staged mode valve of the first dual-stage oxygen-fuel burner, and actuate the main oxygen valve and the staged mode valve of the second dual-stage oxygen-fuel burner, for adjusting the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

[0009] Aspect 2. A system according to Aspect 1, wherein each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner includes a central preburner configured and arranged to receive a fuel flow and a main oxygen flow, which is configured and arranged to receive an upper staged port for an upper staged oxygen flow, and a lower staged port configured and arranged to receive a lower staged oxygen flow, wherein the oxygen flow supplied to each of the first and second dual-stage oxygen-fuel burners is the sum of the main oxygen flow and the staged oxygen flow, and wherein the staged oxygen flow is the sum of the upper staged oxygen flow and the lower staged oxygen flow.

[0010] Aspect 3. A system according to Aspect 2, wherein the main oxygen valve of each of the first and second dual-stage oxygen-fuel burners is configured and arranged to actuate between a main flame position and a staged flame position, in which the majority of the oxygen flow is allocated to the main oxygen flow, and in the staged flame position, the majority of the oxygen flow is allocated to the staged oxygen flow; and wherein the staged mode valve of each of the first and second dual-stage oxygen-fuel burners is configured and arranged to actuate between at least two positions, the two positions being selected from: a foam mode position, in which the majority of the staged oxygen flow is allocated to the upper staged oxygen flow; a split mode position, in which the staged oxygen flow is allocated between the upper staged oxygen flow and the lower staged oxygen flow; and a melting mode position, in which the majority of the staged oxygen flow is allocated to the lower staged oxygen flow.

[0011] Aspect 4. A system according to aspect 1, wherein a first group of regenerative air-fuel burners are located in a first wall and a second group of regenerative air-fuel burners are located in a second wall, the furnace further comprising a charging wall perpendicular to the first wall and the second wall and interconnected therebetween.

[0012] Aspect 5. The system of aspect 4, wherein the first dual stage oxy-fuel burner is located between the first set of air-fuel burners and the charge wall, and wherein the second dual stage oxy-fuel burner is located between the second set of air-fuel burners and the charge wall.

[0013] Aspect 6. The system according to aspect 1, wherein the first group of regenerative air-fuel burners and the second group of regenerative air-fuel burners are both located in a wall that is perpendicular to the first wall and the second wall and interconnected therebetween.

[0014] Aspect 7. A system according to Aspect 4, wherein when the controller receives a signal that the first group of air-fuel burners is burning and the second group of burners is storing heat, the controller sends a signal to actuate the main oxygen valve of the first dual-stage burner to a staged position, and actuate the staged mode valve of the first dual-stage oxygen-fuel burner to a melting mode position, and actuate the main oxygen valve of the second dual-stage oxygen-fuel burner to a main flame position, and actuate the staged mode valve of the second dual-stage oxygen-fuel burner to a diversion mode position; and wherein when the controller receives a signal that the second group of air-fuel burners is burning and the first group of burners is storing heat, the controller sends a signal to actuate the main oxygen valve of the first dual-stage burner to the main flame position, and actuate the staged mode valve of the first dual-stage oxygen-fuel burner to a diversion mode position, and actuate the main oxygen valve of the second dual-stage oxygen-fuel burner to a staged position, and actuate the staged mode valve of the second dual-stage oxygen-fuel burner to a melting mode position.

[0015] Aspect 8. The system according to Aspect 7 further includes at least one of: a first bottom thermocouple, which is positioned to measure the bottom temperature of the glass near the first wall and the charging wall; a second bottom thermocouple, which is positioned to measure the bottom temperature of the glass near the second wall and the charging wall; and a top thermocouple, which is positioned to measure the top temperature near the charging wall; wherein the controller is further programmed to receive signals indicating these respective temperatures from at least one of the first bottom thermocouple, the second bottom thermocouple and the top thermocouple; and in response to these signals from the furnace control system and at least one of the following: the first bottom thermocouple, the second bottom thermocouple and the top thermocouple, send signals to actuate the main oxygen valve and the staged mode valve of the first dual-stage oxygen-fuel burner, and actuate the main oxygen valve and the staged mode valve of the second dual-stage oxygen-fuel burner, for adjusting the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

[0016] Aspect 9. A method for synchronous oxygen-fuel combustion of a regenerative glass melting furnace, the regenerative glass melting furnace having a first group of regenerative air-fuel burners and a second group of regenerative air-fuel burners; a first dual-stage oxygen-fuel burner installed in a first wall of the furnace; and a second dual-stage oxygen-fuel burner installed in a second wall of the furnace; each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner includes a central preburner configured and arranged to receive a fuel flow and a main oxygen flow, an upper step port configured and arranged to receive an upper step oxygen flow, and a lower step port configured and arranged to receive a lower step oxygen flow, the method comprising the following steps: alternately burning the first group of air-fuel burners and the second group of air-fuel burners so that When the first group of air-fuel burners is burning, the second group of air-fuel burners is storing heat, and when the first group of air-fuel burners is storing heat, the second group of air-fuel burners is burning; detecting which of the first and second groups of air-fuel burners is burning, and which of the first and second groups of air-fuel burners is storing heat; and according to which of the first and second groups of air-fuel burners is burning, and which of the first and second groups of air-fuel burners is storing heat, controlling the main oxygen flow, the upper stage oxygen flow, and the lower stage oxygen flow to the preburner of each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner, so as to adjust the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

[0017] Aspect 10. The method according to aspect 9, wherein the oxygen flow supplied to the first dual-stage oxygen-fuel burner is the sum of the main oxygen flow and the staged oxygen flow, and wherein the staged oxygen flow is the sum of the upper staged oxygen flow and the lower staged oxygen flow.

[0018] Aspect 11. The method according to aspect 9, wherein a first group of regenerative air-fuel burners are located in a first wall and a second group of regenerative air-fuel burners are located in a second wall, the furnace further comprising a charging wall perpendicular to the first wall and the second wall and interconnected therebetween.

[0019] Aspect 12. The method of aspect 11, wherein the first dual stage oxy-fuel burner is located between the first set of air-fuel burners and the charge wall, and wherein the second dual stage oxy-fuel burner is located between the second set of air-fuel burners and the charge wall.

[0020] Aspect 13. The method according to aspect 9, wherein the first group of regenerative air-fuel burners and the second group of regenerative air-fuel burners are both located in a wall that is perpendicular to the first wall and the second wall and interconnected therebetween.

[0021] Aspect 14. The method according to Aspect 11, wherein the first wall of the furnace is located on the right side of the charging wall and the second wall of the furnace is located on the left side of the charging wall, further comprising the following steps: when the first group of air-fuel burners is burning and the second group of burners is storing heat, actuating the main oxygen valve of the first dual-stage burner to the staged position, actuating the staged mode valve of the first dual-stage oxygen-fuel burner to the melting mode position, and actuating the main oxygen valve of the second dual-stage oxygen-fuel burner to the main flame position, and actuating the staged mode valve of the second dual-stage oxygen-fuel burner to the diversion mode position; and when the second group of air-fuel burners is burning and the first group of burners is storing heat, actuating the main oxygen valve of the first dual-stage burner to the main flame position, actuating the staged mode valve of the first dual-stage oxygen-fuel burner to the diversion mode position, and actuating the main oxygen valve of the second dual-stage oxygen-fuel burner to the staged position, and actuating the staged mode valve of the second dual-stage oxygen-fuel burner to the melting mode position.

[0022] Aspect 15. The method according to Aspect 14 further includes measuring at least one of the following: the bottom temperature of the first glass near the first wall and the loading wall, the bottom temperature of the second glass near the second wall and the loading wall, and the top temperature near the loading wall; and controlling the main oxygen flow, the upper staged oxygen flow, and the lower staged oxygen flow to the preburner of each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner according to which of the first and second groups of air-fuel burners is burning and which of the first and second groups of air-fuel burners is storing heat, the measured first glass bottom temperature, the measured second glass bottom temperature, and the measured top temperature, so as to adjust the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

[0023] Various aspects of the systems disclosed herein may be used alone or in combination with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A top schematic diagram of a side port regenerative furnace showing a zero port oxy-fuel booster burner illustrating that a recirculating gas zone may form between the charge wall and the port 1 air fuel burner which may cause the booster burner flame to deflect or be drawn into the nearby port 1 air fuel flame.

[0025] Figure 2 CFD modeling results showing a top view of a regenerative furnace with a zero-port oxy-fuel booster burner, illustrating the effect of recirculation patterns near the booster burner (far left in the figure) that can cause booster burner flame deflection.

[0026] Figure 3 Shows Figure 2 CFD modeling results of the furnace side view.

[0027] Figure 4 Photograph of a front perspective view of a dual stage oxy-fuel burner on the hot face of a burner block showing the central main nozzle (fuel and oxygen forming a fuel-rich main flame) and the upper and lower stage ports (flowing oxygen).

[0028] Figure 5A , Figure 5B and Figure 5C To show Figure 4 Schematic diagram of various staging modes of a two-stage burner. In the foam mode ( Figure 5A ), oxygen is staged primarily above the main flame to produce a long flame with a soot sublayer containing reducing gases (CO) for foam destabilization. Figure 5B ), oxygen is staged above and below the main flame to produce a high momentum, high brightness flame that operates well in high turbulence locations. Figure 5C In the process, oxygen is mainly staged below the main flame to produce a long flame with a glowing bottom surface for high intensity melting with top protection.

[0029] Figure 6 A photograph of the rear view of a two-stage oxy-fuel burner with pneumatic actuators installed to achieve automatic control of the staging mode and main oxygen (staging) valve.

[0030] Figure 7 A schematic diagram illustrating an embodiment of a synchronous oxy-fuel combustion system includes two dual-stage burners installed in a zero port position, two pneumatic control boxes, and a controller configured to control the system.

[0031] Figure 8 Schematic plan view of a regenerative furnace with oxy-fuel combustion burners showing the location of the bottom thermocouple.

[0032] Fig. 9 A graphical summary showing the results of bottom temperature variation for asynchronous and synchronous two-stage combustors relative to an asynchronous single-stage combustor.

[0033] Fig. 10A , Fig. 10B and Fig. 10C Photographs comparing combustion of an oxy-fuel burner on the left to the opposite (right) air-fuel burner. The view is from the throat end (discharge end) wall looking back toward the charge wall. Fig. 10A A single-stage burner with minimal staging is shown; Fig. 10B A two-stage burner without synchronous combustion is shown; and Fig. 10C A two-stage burner with synchronous combustion is shown. The black dashed line represents the same location on the charge end wall in each photo.

[0034] Fig.11 A schematic diagram of the furnace plan is shown, showing the location of the furnace top thermocouple closest to the auxiliary burner.

[0035] Fig.12 Graph comparing the average top thermocouple temperature of the closest auxiliary burner for asynchronous and synchronous two-stage burners relative to an asynchronous single-stage burner.

[0036] Fig.13 Graph comparing glass defects (both bubbles and stones) per ton of glass for asynchronous and synchronous two-stage burners relative to asynchronous single-stage burners.

[0037] Fig.14 To illustrate the graphs of average specific furnace energy consumption, corrections were made for the change in cullet percentage for the asynchronous and synchronous two-stage burners relative to the asynchronous single-stage burner.

[0038] Fig.15 A plan view of an end-port regenerative furnace without oxy-fuel combustion burners, showing the circulation path of the combustion products within the furnace.

[0039] Fig.16 Schematic plan view of an end-ported regenerative furnace with oxy-fuel combustion burners. DETAILED DESCRIPTION

[0040] To maximize the benefits of oxygen-assisted combustion and overcome current challenges, the inventors developed a synchronized combustion system that automatically adjusts flame characteristics (particularly length, brightness and momentum) each time the regenerator is reversed. The synchronized combustion system allows furnace engineers to customize the settings of each burner's two combustion directions according to specific airflow and flame conditions. Such a system can ensure that the flame quality of each burner is maximized to overcome the negative effects of turbulence generated by the regenerator reverse cycle.

[0041] The synchronous combustion system uses a two-stage burner 20, such as Figure 4 As shown, it is described in detail in U.S. Patent No. 10,584,051, which is incorporated herein by reference. The two-stage burner is designed to achieve a high degree of oxygen staging with high momentum and high brightness; the flame characteristics are ideal for oxygen-fuel combustion applications. The two-stage burner has a high degree of adjustability and includes two valves that control the direction and amount of staging oxygen. These valves are referred to as the staging mode valve and the main oxygen valve in this article. The performance of the two-stage burner in combustion-supporting applications is compared with the early single-stage burner (see U.S. Patent No. 7,390,189). In addition, the present disclosure shows the impact on the performance of the two-stage burner added synchronously with the operation of the regenerative furnace. This article describes the impact of various furnace operating parameters of single-stage burner combustion, two-stage burner combustion without a synchronization system, and synchronized two-stage burner combustion in three cases, including the impact on energy consumption, local furnace temperature and glass defects.

[0042] The synchronous combustion system is significantly more effective due to the high adjustability of the dual-stage burner in controlling flame characteristics such as momentum, length and brightness. The dual-stage burner is a flat flame oxy-fuel burner designed for the glass industry that has several features including increased flame radiation for improved fuel efficiency, reduced foaming capacity, reduced glass defects and reduced NOx emissions.

[0043] The burner block of the dual stage burner 20 has three ports; a central preburner port 24 where the fuel and main oxygen begin combustion and the flame takes root and stabilizes; an upper oxygen staging port 22 and a lower oxygen staging port 26. The dual stage burner 20 has a unique oxygen staging capability where the staging oxygen can be directionally controlled and proportioned through one or both of the upper or lower staging ports near the main preburner via a staging mode valve 30. The oxygen staging modes include a foam control mode, a melting mode, and a diversion mode. This directional control of staging oxygen provides several benefits, including adjusting flame length, momentum, brightness, and gas atmosphere near the glass surface. FIG. 5A to FIG. 5C Various staging modes are described for the dual stage burner 20. Oxygen staging further prevents NOx formation by delaying the mixing of oxygen with the natural gas, thereby reducing flame temperatures.

[0044] The staged mode valve 30 can realize the following three different burner operation modes:

[0045] Divide mode. In diverter mode, Figure 5B As shown, substantially equal amounts of oxygen are directed to the upper oxygen staging port 22 and the lower oxygen staging port 26. This results in a shorter, brighter flame with relatively high momentum that remains stable even in an opposing turbulent environment. The split flow mode is particularly useful when the booster burner is firing from the exhaust side of a regenerative furnace.

[0046] Melting mode. In melting mode, Figure 5C As shown, oxygen is directed to the lower oxygen staging port 26 of the burner block, which is located below the main flame. The flame will form a bright underside due to thermal radiation caused by the local combustion of the staging oxygen and fuel on the underside of the flame jet. Since the soot formed in the jet with a higher fuel content acts as an optical shield that limits upward radiation, the high radiation generated in the melting mode is preferentially directed downward to the glass surface and has been shown to accelerate the melting process.

[0047] Foam mode. In foam mode (or foam control mode), if Figure 5A As shown, oxygen is directed to the upper oxygen staging port 22 of the burner block, which is located above the main flame. The resulting flame soot bottom layer contains reducing gases composed mainly of carbon monoxide (concentration of several percent). The reducing atmosphere generated by the flame extends above the glass surface and serves to dissipate surface foam.

[0048] The main oxygen valve 28 is used to moderate the combustion characteristics of each of the three staging modes described above. When the main oxygen valve 28 is 100% open, approximately 75% of the total oxygen entering the burner passes through the main nozzle and enters the central burner block (preburner) passage. This condition enhances the mixing between the oxygen and natural gas in the central nozzle and produces a shorter, more stable, and more powerful flame. When the main oxygen valve 28 is closed, approximately 5% of the burner oxygen flow is discharged through the main nozzle, and the remaining (95%) oxygen flow is distributed to the upper and / or lower staging ports according to the selected staging mode. When the main oxygen valve 28 is closed, maximum oxygen staging can be achieved and the flame length will be the maximum value for a given fuel flow (combustion) rate. In addition, due to the formation of a large amount of intermediate soot, NOx emissions will be reduced and flame brightness will increase. In addition, as the main oxygen valve is gradually closed, the flame momentum decreases over time.

[0049] The synchronized booster system enables optimum booster burner flame characteristics, particularly length, brightness and momentum associated with each regenerator reversal cycle in the air fired side port furnace. This is achieved via automatic remote control of the flame characteristics using pneumatic or electric actuation of the burner staged mode valve 30 and the main oxygen valve 28. In a preferred embodiment, the burner is provided with pneumatic actuators for both oxygen valves 28, 30. The arrangement of typical pneumatic actuators on both valves is shown in FIG. Figure 6. Pneumatic actuators are typically double acting, so each actuator is capable of achieving two different control positions, which can be preset using mechanical stops. The synchronized burner control system works in conjunction with the equipment or furnace overall control system to change the valve position to the optimal default position during each regenerator reversal cycle. For example, during the initial system setup, the optimal burner setting can be determined by visual observation of the booster burner flame and optical temperature measurement of the charge wall and breast wall near the booster burner. This may be an iterative process involving assessment of flame quality and appearance, as well as measurement of local refractory temperatures at different valve settings. It should be noted that the optimal valve position may vary due to various factors, including but not limited to local turbulence near the booster burner, changing airflow patterns due to different furnace geometries of different installations, firing rate of the booster burner, fuel distribution of the air burner, and flow of the regenerator. Subsequently, the optimal valve position setting is programmed into the synchronized system to ensure that the staged mode valve moves to the optimal position during each reversal cycle.

[0050] Note that while dual-stage burners are well suited for co-firing due to the ability to widely adjust the combustion characteristics of the flame, even oxy-fuel burners with single-stage oxygen staged mode valves (eg US 7,390,189) can be easily adapted to the system of the present invention.

[0051] like Figure 7 As shown, the synchronized combustion system 100 uses a controller, such as a programmable logic controller (PLC) 40, which receives a signal indicating when the reversal occurs from a furnace distributed control system (DCS) 42. The PLC then sends a signal to the solenoids 44A and 44B, respectively, to drive the pneumatic actuators corresponding to the staged mode valves 30 installed on each combustion burner 20A and 20B, respectively. Figure 7 A typical layout of the components of the synchronous combustion system 100 is depicted.

[0052] In another embodiment, some regenerative glass furnaces use an end port air fuel burner configuration. Fig.15An end port furnace 110 is shown with a first regenerator 112B having a first set of air-fuel burner ports 130B burning air-fuel flames 132, while a second regenerator 112A having a second set of air-fuel burner ports 130A is exhausting, wherein both regenerators 112B and 112A are located in a charging end 114 of the furnace 110. Each set of burner ports 130A and 130B may include one or more air-fuel burners. Hot combustion products 134 circulate on the melt toward a discharge end 116 of the furnace 110, after which they are recirculated and exit the furnace 110 as flue gas 136. Solid charge is added to the furnace 110 via a charging port 140, and molten glass exits the furnace as shown by flow arrows G. In a conventional cycle, the regenerators are reversed so that the first regenerator 112B is exhausting, while the second regenerator 112A is burning. The first side wall 118B and the second side wall 118A opposite the first side wall 118B connect the loading end 114 to the discharge end 116 .

[0053] Fig.16 The simultaneous addition of oxy-fuel combustion-supporting burners 120A and 120B to the furnace 110 is shown. The first oxy-fuel combustion-supporting burner 120B is located in the first side wall 118B, and the second oxy-fuel combustion-supporting burner 120A is located in the second side wall 118A. Although the combustion-supporting burners 120A and 120B are located in opposing side walls 118A and 118B, they are not necessarily directly opposite. As with the side-ported regenerative furnace 10, the operation of the oxy-fuel combustion-supporting burners 120A and 120B is synchronized with the reverse cycle of the air-fuel regenerators 112A and 112B to optimize performance.

[0054] Example in a side-port regenerative furnace

[0055] A synchronized combustion system was developed and installed on a 650 tons / day (“tpd”) float glass furnace with a side-port configuration. The system replaced a single-stage burner that was operated without synchronized staging. An intermediate operating phase using a two-stage burner without synchronization was also performed. The performance comparison results of these three operating phases were verified over several months of operation. The results for local glass and refractory top temperatures, glass defects and furnace melting efficiency are presented.

[0056] During the test, the key parameters independent of the furnace included the glass pulling (production) rate, the firing rate of each of the two booster burners, and the percentage of cullet (recycled glass) mixed with the original glassmaking material. The pulling rate was maintained within + / - 2% of the nominal 650 tpd setting, while the booster burner firing rate was maintained at a constant value of 8.25 MMBtu / h / burner. As shown in Table 1, the cullet was slightly different at each stage.

[0057] Table 1 - Average percentage of broken glass at each test stage

[0058] Burner Type: Single-stage burner without synchronization Two-stage burner without synchronization Two-stage synchronous burner Average glass cullet (%) 18 21.7 20

[0059] Before actuating the synchronous combustion system, the flame characteristics and therefore the default staging mode valve positions were manually optimized. Visual observation and optical temperature measurements using a 1 micron handheld pyrometer were performed to determine the optimal staging mode and main oxygen valve settings for each burner and reverse combustion cycle.

[0060] Table 2 below shows the optimum valve settings determined during testing for a dual stage burner with a synchronized booster system. The optimum valve settings were selected for this particular situation based on the local conditions during testing. The optimum valve settings may change over time for the same installation or different installations due to various factors, including but not limited to local turbulence near the booster burner, changing gas flow patterns due to different furnace geometries for different installations, firing rates for oxy-fuel booster burners, fuel distribution for air-fired burners, and regenerator flow. In general, the optimum conditions for an oxy-fuel booster burner firing opposite an air-fired burner include increasing the primary oxygen flow and changing the staging mode to a split mode to provide a higher momentum flame. The general optimum conditions for an oxy-fuel booster burner firing on the same side as an air-fired burner include reducing the primary oxygen (increasing the staging oxygen) and setting the staging mode to a melt mode to maximize heat transfer to the batch material below. The exact valve settings to determine the optimum should be determined in the field based on observations of flame and / or temperature indicators, including but not limited to furnace thermocouples and / or optical temperature measurements. A number of main oxygen and staged oxygen flows that may typically encompass optimal conditions include the following: for an oxygen-fuel-assisted burner firing opposite to an air-assisted burner, 60% to 90% main oxygen flow and the remaining (40% to 10%) staged oxygen flow; for an oxygen-fuel-assisted burner firing in the same direction as an air-assisted burner, 5% to 40% main oxygen flow and the remaining (95% to 60%) staged oxygen flow.

[0061] Tables 3 and 4 show similar information for an asynchronous two-stage burner and an asynchronous single-stage burner, respectively.

[0062] Table 2 - Optimized classification settings for two-stage synchronous combustion-supporting burners

[0063]

[0064] Table 3 - Classification of two-stage asynchronous combustion-supporting burners

[0065] Auxiliary burner position Grading Mode Primary oxygen (open percentage) Left burner Shunt 50 Right burner Shunt 75

[0066] Table 4 - Classification of single-stage asynchronous combustion-supporting burners

[0067]

[0068] result

[0069] Effect on glass bottom temperature. Increasing the bottom temperature enhances the natural circulation current in the glass melt, increases the glass residence time, and thus reduces the number of gas inclusions (seeds or bubbles) in the glass product. The glass bottom temperature is recorded on the left and right sides of the furnace, with the nearest thermocouple 46A (right side, at Fig. 9 ) and 46B (left side, marked as "R" in the diagram Fig. 9 The bottom of the fuel tank is marked "L" on the diagram of the fuel tank. Figure 8 shown.

[0070] Fig. 9 The normalized temperature difference (ΔT) of the average bottom temperature for the two-stage burners (synchronized "Sync" and unsynchronized "HRx") is shown. The results shown here are normalized to the measurements of the single-stage burner without synchronization installed before the start of the test. The average bottom temperature increased by 6℉ in the two-stage synchronous combustion case compared to the single-stage burner. In addition, the changes in the left and right thermocouples are almost the same, which means that the flame is stable and balanced during both the combustion and exhaust parts of the regenerator cycle. In contrast, the average bottom temperature of the two-stage burner without synchronous combustion showed different results. Specifically, the lower left thermocouple is slightly higher than the single-stage burner, while the lower right thermocouple is slightly lower. The imbalance between the left and right sides can be attributed to flame instability, which is due to the lack of burner synchronization and the lack of optimal flame in both halves of the regenerator cycle.

[0071] In addition, the "average" relative performance of the burners with respect to glass bottom temperature can be referenced to Fig. 10A , Fig. 10B and Fig. 10C The flame photographs shown in are qualitatively understood and were taken during the exhaust phase of the regenerator cycle. Fig. 10A The flame of the single-stage asynchronous burner is diffused due to the turbulence. Fig. 10B The flame of the mid-two-stage asynchronous burner appears straighter and more consistent, but the grading is limited to keeping the flame characteristics consistent when firing in reverse in the furnace. Fig. 10C The longer, brighter flame of the dual-stage synchronous burner maximizes staging, resulting in better heat transfer to the batch. In summary, these photos highlight the dual-stage synchronous combustion burner ( Fig. 10C ) relative to the two asynchronous cases ( Fig. 10A and Fig. 10B ) to achieve a longer, brighter flame. Fig. 10C The longer, brighter flame obviously has a larger surface area and higher emissivity, which will result in a higher rate of heat transfer from the flame to the glass; therefore, a higher bottom temperature.

[0072] Effect on furnace top temperature. Operating at relatively low top temperatures is desirable because of the life of the refractory material and to reduce refractory-based glass defects (stone). The top thermocouple 48 closest to the furnace 10 to the auxiliary burners 20A and 20B is located centrally between the auxiliary burners 20A and 20B, about 12 feet from the charge end wall, and within about 4 feet below the burner oil tank, as shown in FIG. Fig.11 shown.

[0073] Fig.12 The average temperature difference of the local top thermocouples of the dual-stage burners (with and without Sync) and the single-stage burner results are shown. The average temperature of the dual-stage burner without Sync ("HRx") was reduced by about 7°F compared to the previously installed single-stage burner. This is mainly because the dual-stage burner has a higher flame momentum than the single-stage burner and can achieve a higher degree of lower flame staging. As described in U.S. Patent No. 10,584,051, the higher the degree of lower flame staging, the denser the layer of soot particles above the flame, which hinders the radiant flame energy from being transferred upward to the top. In addition, the higher momentum of the dual-stage burner prevents the flame from tilting toward the top to a certain extent, which also reduces the top temperature. The average top temperature of the dual-stage burner with synchronized combustion ("Sync") was reduced by about 12°F. This result highlights the effectiveness of the Sync system, in which the flame characteristics of the dual-stage burner are fully optimized to maximize flame brightness and momentum, thereby transferring a higher proportion of heat to the glass melt.

[0074] Effect on glass defects. The glass defect data for bubbles and stones are calculated based on the average number of defects per ton of produced glass. Compared with the single-stage burner data, the defect data for the two-stage burner with and without synchronization are normalized again, such as Fig.13 The results for the dual-stage synchronous combustion system showed an 8% and 21% reduction in bubbles and stones, respectively. Logically, these favorable results come from the increase in bottom glass temperature, and the reduction in top temperature achieved using the synchronous system. That is, as previously mentioned, higher bottom temperatures lead to fewer bubbles due to the enhanced natural circulation within the glass melt, while lower top temperatures reduce the amount of refractory flowing into the glass, thereby reducing "stones." The dual-stage burner without synchronous combustion showed a slight increase in defect bubbles, considering that Fig. 9 The average bottom temperature shown (average of the left and right thermocouples) is slightly lower, which is not unexpected. Also, the two-stage burner had 12% less stone without co-firing, which is probably also due to the lower top temperature.

[0075] Specific Energy Consumption. The furnace specific energy consumption is the most difficult parameter to evaluate because it is an indirect calculation involving multiple test variables, not all of which are controlled during the test procedure. Specifically, energy consumption is evaluated by multiplying the total natural gas consumption rate for the air-fuel burners by the natural gas heating value and dividing by the total tons of glass produced during the evaluation period. The energy consumption results are then corrected for the change in the average percentage of cullet used in each of the three test cycles. Fig.14 The results shown indicate that the corrected energy consumption for the two dual-stage burners is approximately 2.5% lower than that of the single-stage burner. It should be noted that the energy consumption results may be affected by the furnace control system, which was put into operation before the start of the test. The control system is not of the traditional type that directly regulates the fuel flow rate based on critical furnace temperature. Instead, it adjusts the air-fuel rate based on a complex non-linear algorithm derived from continuous learning / data reduction. Therefore, hardware (oxy-fuel burners) and operational changes (burner synchronization) made between test phases may have affected the learning pattern and control response. Even so, it is clear that the dual-stage burners (with and without synchronization) reduce energy consumption compared to the baseline single-stage burner.

[0076] In summary, the Synchronous Combustion System is designed to overcome the high turbulence and changing airflow inherent in oxygen combustion in air-fired regenerative side-port furnaces. The performance of oxyfuel burners is improved by allowing customized flame characteristics (momentum, brightness) to be automatically set for each burner in each regenerative reversal cycle. The test results described in this article show that the Synchronous Combustion System is able to produce more favorable furnace top and bottom temperatures and significantly improve glass quality with a 2-3% reduction in energy consumption.

[0077] The scope of the present invention is not limited by the specific aspects or embodiments disclosed in the examples, which are intended to illustrate several aspects of the present invention, and any embodiments that are functionally equivalent are within the scope of the present invention. Various modifications of the present invention, in addition to those shown and described herein, will become apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Claims

1. A system for synchronous oxy-fuel combustion of a regenerative glass melting furnace, the regenerative glass melting furnace having a first group of regenerative air-fuel burners and a second group of regenerative air-fuel burners, and a furnace control system, the furnace control system being programmed to control the alternating combustion of the first group of air-fuel burners and the second group of air-fuel burners, so that when the first group of air-fuel burners is burning, the second group of air-fuel burners is storing heat, and when the first group of air-fuel burners is storing heat, the second group of air-fuel burners is burning, the system include: a first dual stage oxy-fuel burner mounted in a first wall of the furnace and having a main oxygen valve to distribute the oxygen flow between the main oxygen and the staged oxygen, and a staged mode valve to distribute the staged oxygen flow between the upper stage port and the lower stage port; a second dual-stage oxy-fuel burner mounted in a second wall of the furnace, the second wall being opposite the first wall, and having a main oxygen valve to distribute the oxygen flow between a main oxygen flow and a staged oxygen flow, and a staged mode valve to distribute the staged oxygen flow between an upper staged oxygen flow to the upper staged port and a lower staged oxygen flow to the lower staged port; as well as A controller programmed to: receiving a signal from the furnace control system indicating which of the first and second groups of air-fuel burners are firing and which of the first and second groups of air-fuel burners are storing heat; as well as In response to the signal from the furnace control system, a signal is issued to actuate a main oxygen valve and a staged mode valve of the first dual-stage oxygen-fuel burner, and to actuate a main oxygen valve and a staged mode valve of the second dual-stage oxygen-fuel burner to adjust flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

2. The system of claim 1 , wherein each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner comprises a central preburner configured and arranged to receive a fuel flow and the primary oxygen flow, an upper staged port configured and arranged to receive the upper staged oxygen flow, and a lower staged port configured and arranged to receive the lower staged oxygen flow, wherein the oxygen flow supplied to each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner is the sum of the primary oxygen flow and the staged oxygen flow, and wherein the staged oxygen flow is the sum of the upper staged oxygen flow and the lower staged oxygen flow.

3. The system according to claim 2, wherein said main oxygen valve of each of said first dual stage oxy-fuel burner and said second dual stage oxy-fuel burner is configured and arranged to actuate between a main flame position, in which a majority of said oxygen flow is allocated to said main oxygen flow, and a staged flame position, in which a majority of said oxygen flow is allocated to said staged oxygen flow; and Wherein the staged mode valve of each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner is configured and arranged to actuate between at least two positions selected from a foam mode position, a diverter mode position and a melting mode position: in the foam mode position, most of the staged oxygen flow is allocated to the upper staged oxygen flow; in the diverter mode position, the staged oxygen flow is allocated between the upper staged oxygen flow and the lower staged oxygen flow; in the melting mode position, most of the staged oxygen flow is allocated to the lower staged oxygen flow.

4. The system of claim 1 , wherein the first set of regenerative air-fuel burners are located in the first wall and the second set of regenerative air-fuel burners are located in the second wall, the furnace further comprising a charging wall perpendicular to and interconnected between the first wall and the second wall.

5. The system of claim 4, wherein the first dual stage oxy-fuel burner is located between the first set of air-fuel burners and the charge wall, and wherein the second dual stage oxy-fuel burner is located between the second set of air-fuel burners and the charge wall.

6. The system of claim 1, wherein the first set of regenerative air-fuel burners and the second set of regenerative air-fuel burners are both located in walls that are perpendicular to and interconnected between the first wall and the second wall.

7. The system according to claim 4, wherein the main oxygen valve of each of the first dual-stage oxy-fuel burner and the second dual-stage oxy-fuel burner is configured and arranged to actuate between a main flame position, in which a majority of the oxygen flow is allocated to the main oxygen flow, and a staged flame position, in which a majority of the oxygen flow is allocated to the staged oxygen flow; and wherein the staged mode valve of each of the first dual-stage oxy-fuel burner and the second dual-stage oxy-fuel burner is configured and arranged to actuate between at least two positions selected from a foam mode position, a split mode position, and a melt mode position: in the foam mode position, a majority of the staged oxygen flow is allocated to the upper staged oxygen flow; in the split mode position, the staged oxygen flow is allocated between the upper staged oxygen flow and the lower staged oxygen flow; in the melt mode position, a majority of the staged oxygen flow is allocated to the lower staged oxygen flow; wherein when the controller receives a signal that the first group of air-fuel burners is burning and the second group of air-fuel burners is storing heat, the controller sends a signal to actuate the main oxygen valve of the first dual-stage oxygen-fuel burner to the staged flame position, actuate the staged mode valve of the first dual-stage oxygen-fuel burner to the melting mode position, actuate the main oxygen valve of the second dual-stage oxygen-fuel burner to the main flame position, and actuate the staged mode valve of the second dual-stage oxygen-fuel burner to the diversion mode position; and When the controller receives a signal that the second group of air-fuel burners is burning and the first group of air-fuel burners is storing heat, the controller sends a signal to actuate the main oxygen valve of the first two-stage oxygen-fuel burner to the main flame position, and actuate the staged mode valve of the first two-stage oxygen-fuel burner to the diversion mode position, and actuate the main oxygen valve of the second two-stage oxygen-fuel burner to the staged flame position, and actuate the staged mode valve of the second two-stage oxygen-fuel burner to the melting mode position.

8. The system of claim 7, further comprising at least one of: a first bottom thermocouple positioned to measure the bottom temperature of the glass proximate the first wall and the charge wall; ； a second bottom thermocouple positioned to measure the temperature of the bottom of the glass proximate the second wall and the charge wall; and a top thermocouple positioned to measure the top temperature near the charge wall; wherein the controller is further programmed to receive a signal from at least one of the first bottom thermocouple, the second bottom thermocouple, and the top thermocouple indicating a respective temperature; and in response to the signal from the at least one of the first bottom thermocouple, the second bottom thermocouple and the top thermocouple and the furnace control system, sending a signal to actuate the main oxygen valve and the staged mode valve of the first dual-stage oxygen-fuel burner and actuate the main oxygen valve and the staged mode valve of the second dual-stage oxygen-fuel burner to adjust the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

9. A method for synchronous oxy-fuel combustion of a regenerative glass melting furnace having a first set of regenerative air-fuel burners and a second set of regenerative air-fuel burners, a first dual-stage oxy-fuel burner mounted in a first wall of the furnace, and a second dual-stage oxy-fuel burner mounted in a second wall of the furnace ； Each of the first dual-stage oxy-fuel burner and the second dual-stage oxy-fuel burner includes a central preburner configured and arranged to receive a fuel flow and a main oxygen flow, an upper stage port configured and arranged to receive an upper stage oxygen flow, and a lower stage port configured and arranged to receive a lower stage oxygen flow, the method comprising: Alternatingly burning a first group of air-fuel burners and a second group of air-fuel burners, so that when the first group of air-fuel burners are burning, the second group of air-fuel burners are storing heat, and when the first group of air-fuel burners are storing heat, the second group of air-fuel burners are burning; detecting which of the first and second groups of air-fuel burners are firing and which of the first and second groups of air-fuel burners are accumulating heat; and Based on which of the first and second groups of air-fuel burners is burning and which of the first and second groups of air-fuel burners is storing heat, the main oxygen flow, the upper staged oxygen flow, and the lower staged oxygen flow to the preburner with respect to each of the first and second dual-stage oxygen-fuel burners are controlled to adjust the flame characteristics of the first and second dual-stage oxygen-fuel burners.

10. The method of claim 9, wherein the oxygen flow supplied to the first dual-stage oxy-fuel burner is the sum of the main oxygen flow and a staged oxygen flow, and wherein the staged oxygen flow is the sum of the upper staged oxygen flow and the lower staged oxygen flow.

11. The method of claim 9, wherein the first group of regenerative air-fuel burners are located in the first wall and the second group of regenerative air-fuel burners are located in the second wall, the furnace further comprising a charging wall perpendicular to and interconnected between the first wall and the second wall.

12. The method of claim 11, wherein the first dual stage oxy-fuel burner is located between the first set of air-fuel burners and the charge wall, and wherein the second dual stage oxy-fuel burner is located between the second set of air-fuel burners and the charge wall.

13. The method of claim 9, wherein the first group of regenerative air fuel burners and the second group of regenerative air fuel burners are both located in walls perpendicular to and interconnected between the first wall and the second wall.

14. The method of claim 11, wherein the first wall of the furnace is located to the right of the charging wall and the second wall of the furnace is located to the left of the charging wall, wherein the main oxygen valve of each of the first dual-stage oxy-fuel burner and the second dual-stage oxy-fuel burner is configured and arranged to actuate between a main flame position, in which a majority of the oxygen flow is allocated to the main oxygen flow, and a staged flame position, in which a majority of the oxygen flow is allocated to the staged oxygen flow; and wherein the staged mode valve of each of the first dual-stage oxy-fuel burner and the second dual-stage oxy-fuel burner is configured and arranged to actuate between at least two positions selected from a foam mode position, a split mode position, and a melt mode position: in the foam mode position, a majority of the staged oxygen flow is allocated to the upper staged oxygen flow; in the split mode position, the staged oxygen flow is allocated between the upper staged oxygen flow and the lower staged oxygen flow; in the melt mode position, a majority of the staged oxygen flow is allocated to the lower staged oxygen flow; The method also include: When the first group of air-fuel burners is burning and the second group of air-fuel burners is storing heat, actuating the main oxygen valve of the first dual-stage oxygen-fuel burner to the staged flame position and actuating the staged mode valve of the first dual-stage oxygen-fuel burner to the melt mode position, and actuating the main oxygen valve of the second dual-stage oxygen-fuel burner to the main flame position and actuating the staged mode valve of the second dual-stage oxygen-fuel burner to the split mode position; as well as When the second group of air-fuel burners is burning and the first group of air-fuel burners is storing heat, the main oxygen valve of the first dual-stage oxygen-fuel burner is actuated to the main flame position, and the staged mode valve of the first dual-stage oxygen-fuel burner is actuated to the diversion mode position, and the main oxygen valve of the second dual-stage oxygen-fuel burner is actuated to the staged flame position, and the staged mode valve of the second dual-stage oxygen-fuel burner is actuated to the melting mode position.

15. The method of claim 14, further comprising measuring at least one of: a first glass bottom temperature near the first wall and the charging wall, a second glass bottom temperature near the second wall and the charging wall, and a top temperature near the charging wall; and Based on which of the first and second groups of air-fuel burners is burning and which of the first and second groups of air-fuel burners is storing heat, the measured first glass bottom temperature, the measured second glass bottom temperature and the measured top temperature, the main oxygen flow, the upper staged oxygen flow and the lower staged oxygen flow to the preburner of each of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner are controlled to adjust the flame characteristics of the first dual-stage oxygen-fuel burner and the second dual-stage oxygen-fuel burner.

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