Float glass is a sheet of glass made by floating molten glass on a bed of molten metal (typically molten tin often referred to as a tin bath). Raw materials (e.g., sand, sodium carbonate, dolomite, limestone, sodium sulfate, etc.) may be mixed and heated by combustion air to form molten glass before being fed onto a bath of molten metal.
The addition of oxygen or oxygen-inclusive gas to the heated combustion air increases the temperature of the glass melt and improves combustion. The oxygen or oxygen-inclusive gas may be provided by an oxygen lance.
In order to cool the oxygen lance, conventional techniques use compressed air or oxygen during a cooling period. The compressed air is provided by a compressed air line which is separate from the line used to provide oxygen or oxygen-inclusive gas. Because contamination (for example, oil contamination) in an oxygen pipeline has the potential to cause an explosion, oxygen systems are especially sensitive to oil and other contaminants. Additional equipment may be needed to provide “oil free” compressed air to the oxygen lances at additional expense. This additional equipment also requires rigorous cleaning procedures during installation at additional expense. Because of the required cleaning procedures and the risk of explosion, oxygen suppliers typically refrain from using compressed air for lance cooling.
Oxygen lances may be cooled with water. Prior art water cooled oxygen lances, however, are costly to manufacture because they require intricate machining to achieve the desired water cooling. The oxygen lance in U.S. Pat. No. 4,702,462, for example, requires three concentric tubes and six tubular nozzles.
Accordingly, there is a need for an improved oxygen lance for use in a float glass furnace and/or a float glass furnace which includes an improved oxygen lance.