Oxygen for combustion in forehearths

A method comprising:

• in a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, maintaining the molten glass in the channels in the molten state by heat of combustion which is provided to the space above the molten glass, by:
• injecting into the space above the molten glass, from one or more air-fuel injectors each of which opens at its own refractory port in a side wall of the channel, a premixed mixture of air and fuel at a velocity greater than 50 ft/sec in which the amount of air in the mixture injected from each air-fuel injector is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the mixture injected from the same injector, and
• injecting into the space above the molten glass, from one or more oxygen injectors each of which opens at its own refractory port in a side wall of the channel, gaseous oxidant containing at least 80 vol. % oxygen at a velocity less than 50 ft/sec and at a rate that provides sufficient oxygen, taken together with the oxygen content of the mixture of air and fuel that is injected from the air-fuel injectors, to completely combust the fuel that is injected from the fuel injectors,
• wherein there is no physical barrier between the molten glass and the space into which the mixture of air and fuel, and the gaseous oxidant, are injected, and
• in the space above the molten glass combusting the fuel injected from the air-fuel injectors with the oxygen in the air and with the oxygen injected from the oxygen injectors so as to generate excess oxygen in the flue gas.

A method comprising:

• from a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, wherein the molten glass in the channels is maintained in the molten state by heat of combustion provided directly to the top surface of the molten glass by combustion in a combustion zone above the molten glass in the forehearth system that contains at least 2 air-fuel burners at which air and fuel fed to the air-fuel burners are combusted to provide the heat of combustion,
• removing at least 50% of said air-fuel burners and replacing them with one or more hybrid burners including a central gaseous oxidant injector pipe and an annular passage for a premixed mixture of air and fuel wherein each hybrid burner opens at its own refractory burner port in a side wall of the channel and is recessed from the hot surface of the side wall, and each hybrid burner is capable of injecting a combustible gas mixture of gaseous oxidant and a premixed mixture of air and fuel into the space in the channel over the molten glass,
• wherein said gaseous oxidant contains at least 80 vol. % oxygen and the amount of air in the premixed mixture is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the premixed mixture and said air-fuel burners are replaced with hybrid burners at a ratio of one hybrid burner for each two to twelve air-fuel burners, that are replaced,
• wherein said gaseous oxidant is injected at a velocity greater than 100 ft/sec, in which the total amount of oxygen in the combustible gas mixture injected from the hybrid burner is sufficient for complete combustion of the fuel injected from the same burner and the flame length is less than the width of the channel,
• wherein there is no physical barrier between the molten glass and the space into which the mixture of oxidant and fuel is injected, and
• combusting the fuel injected from the hybrid burners in the space above the molten glass with excess oxygen in flue gas.

A method comprising:

• in a forehearth system in which molten glass from a glassmelting furnace flows through a channel having refractory side walls, maintaining the molten glass in the channel in the molten state by heat of combustion which is provided directly to the top surface of the molten glass, by:
• injecting a combustible gas mixture into the space above the molten glass from one or more hybrid burners each including a central gaseous oxidant injector pipe and an annular passage for a premixed mixture of air and fuel wherein each hybrid burner opens at its own refractory burner port in a side wall of the channel and is recessed from the hot surface of the side wall, and each hybrid burner is capable of injecting a combustible gas mixture of gaseous oxidant and a premixed mixture of air and fuel into the space in the channel over the molten glass,
• wherein said gaseous oxidant contains at least 80 vol. % oxygen and the amount of air in the premixed mixture is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the premixed mixture,
• wherein said gaseous oxidant is injected at a velocity greater than 100 ft/sec, in which the total amount of oxygen in the combustible gas mixture injected from the hybrid burner is sufficient for complete combustion of the fuel injected from the same burner and the flame length is less than the width of the channel,
• wherein there is no physical barrier between the molten glass and the space into which the mixture of oxidant and fuel is injected, and
• combusting the fuel injected from the hybrid burners in the space above the molten glass with excess oxygen in flue gas.

A method comprising:

• from a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, wherein the forehearth system includes a physical barrier above the molten glass, and wherein the molten glass in the channels is maintained in the molten state by indirect transfer to the molten glass of heat of combustion carried out in the region above the physical barrier, wherein the forehearth system contains a combustion zone above the barrier with at least 2 air-fuel burners at which air and fuel fed to the air-fuel burners are combusted to provide the heat of combustion,
• removing at least 50% of said air-fuel burners and replacing them with one or more air-fuel injectors each of which opens at its own refractory port in a side wall of the channel and each of which is capable of injecting a premixed mixture of air and fuel into a region above the physical barrier over the molten glass, and with one or more oxygen injectors each of which opens at its own refractory port in a side wall of the channel and each of which is capable of injecting gaseous oxidant into a region above the physical barrier over the molten glass,
• wherein the sum of the number of said air-fuel injectors plus the number of said oxygen injectors, which replace said air-fuel burners, is less than the number of air-fuel burners that are removed,
• and then
• injecting from each air-fuel injector into the region above the physical barrier in the channel a premixed mixture of air and fuel at a velocity greater than 50 ft/sec in which the amount of air in the mixture injected from the injector is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the mixture injected from the same injector, and
• injecting from each oxygen injector into the region above the physical barrier in the channel gaseous oxidant containing at least 80 vol. % oxygen at a velocity less than 50 ft/sec and at a rate that provides sufficient oxygen, taken together with the oxygen content of the mixture of air and fuel that is injected from the air-fuel injectors, to completely combust the fuel that is injected from the fuel injectors, and
• in the region above the barrier combusting the fuel injected from the air-fuel injectors with the oxygen in the air and with the oxygen injected from the oxygen injectors so as to generate excess oxygen in flue gas.

A method comprising:

• in a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, wherein the forehearth system includes a physical barrier above the molten glass, maintaining the molten glass in the channels in the molten state by indirect transfer to the molten glass of heat of combustion carried out in the region above the physical barrier, by:
• injecting into the region above the physical barrier, from one or more air-fuel injectors each of which opens at its own refractory port in a side wall of the channel, a premixed mixture of air and fuel at a velocity greater than 50 ft/sec in which the amount of air in the mixture injected from the air-fuel injector is between 25% to 60%, of the stoichiometric air required for complete combustion of the fuel in the mixture injected from the same injector, and
• injecting into the region above the physical barrier, from one or more oxygen injectors each of which opens at its own refractory port in a side wall of the channel, gaseous oxidant containing at least 80 vol. % oxygen at a velocity less than 50 ft/sec and at a rate that provides sufficient oxygen, taken together with the oxygen content of the mixture of air and fuel that is injected from the air-fuel injectors, to completely combust the fuel that is injected from the fuel injectors, and
• in the region above the barrier, combusting the fuel injected from the air-fuel injectors with the oxygen in the air and with the oxygen injected from the oxygen injectors so as to generate excess oxygen in the flue gas.

A method comprising:

• from a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, wherein the forehearth system includes a physical barrier above the molten glass, wherein the molten glass in the channels is maintained in the molten state by indirect transfer to the molten glass of heat of combustion carried out in the region above the physical barrier by combustion, and wherein the forehearth system includes a combustion zone including at least 2 air-fuel burners at which air and fuel fed to the air-fuel burners are combusted to provide the heat of combustion,
• removing at least 50% of said air-fuel burners and replacing them with one or more hybrid burners including a central gaseous oxidant injector pipe and an annular passage for a premixed mixture of air and fuel wherein each hybrid burner opens at its own refractory burner port in a side wall of the channel and is recessed from the hot surface of the side wall, and each hybrid burner is capable of injecting a combustible gas mixture of gaseous oxidant and a premixed mixture of air and fuel into the space in the channel over the molten glass,
• wherein said gaseous oxidant contains at least 80 vol. % oxygen and the amount of air in the premixed mixture is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the premixed mixture and said air-fuel burners are replaced with hybrid burners at a ratio of one hybrid burner for each two to twelve air-fuel burners that are replaced,
• wherein said gaseous oxidant is injected at a velocity greater than 100 ft/sec, in which the total amount of oxygen in the combustible gas mixture injected from the hybrid burner is sufficient for complete combustion of the fuel injected from the same burner and the flame length is less than the width of the channel,
• and combusting the fuel injected from the hybrid burners with excess oxygen in the flue gas in the region above the physical barrier.

A method comprising:

• in a forehearth system in which molten glass from a glassmelting furnace flows through one or more channels having refractory side walls, wherein the forehearth system includes a physical barrier above the molten glass, maintaining the molten glass in the channels in the molten state by indirect transfer to the molten glass of heat of combustion which is carried out in the region above the physical barrier, by:
• injecting a combustible gas mixture into the space above the molten glass from one or more hybrid burners each including a central gaseous oxidant injector pipe and an annular passage for a premixed mixture of air and fuel wherein each hybrid burner opens at its own refractory burner port in a side wall of the channel and is recessed from the hot surface of the side wall, and each hybrid burner is capable of injecting a combustible gas mixture of gaseous oxidant and a premixed mixture of air and fuel into the space in the channel over the molten glass,
• wherein said gaseous oxidant contains at least 80 vol. % oxygen and the amount of air in the premixed mixture is between 25% to 60% of the stoichiometric air required for complete combustion of the fuel in the premixed mixture,
• wherein said gaseous oxidant is injected at a velocity greater than 100 ft/sec, in which the total amount of oxygen in the combustible gas mixture injected from the hybrid burner is sufficient for complete combustion of the fuel injected from the same burner and the flame length is less than the width of the channel,
• and
• combusting the fuel injected from the hybrid burners in the space above the molten glass with excess oxygen in the flue gas.