Furnace and Process for Controlling the Oxidative State of Molten Materials

A method for carrying out combustion comprising:

• (A) injecting into a furnace wherein
• (i) the furnace comprises a charging end, a discharge end, a melting zone adjacent the charging end and a fining zone adjacent the discharge end;
• (ii) the glass forming ingredients are introduced into the melting zone, travel along a path from the melting zone to the fining zone and are withdrawn as molten glass from the fining zone;
• and
• (iii) there is a combustion energy requirement over both the melting zone and the fining zone;
• and
• said furnace contains molten glass, injecting at a point above the molten glass, fuel and primary oxidant in a staged flat-flame configuration and a substoichiometric ratio not exceeding about 70 percent of stoichiometric, said primary oxidant being a fluid comprising at least about 21 mole percent oxygen, both of said fuel and primary oxidant being injected into the furnace at a velocity of about 1000 feet per second or less;
• (B) combusting fuel and primary oxidant within the furnace to produce heat and combustion reaction products including unburned fuel;
• (C) injecting secondary oxidant into the furnace in a flat jet configuration above the injection point of the fuel and primary oxidant, said secondary oxidant being a fluid comprising at least about 21 mole percent oxygen, at a velocity of about 2000 standard feet per second or less;
• (D) establishing a fuel rich gas layer proximate the molten glass, said fuel rich gas layer being more reducing to at least one of the charge or the molten glass than the secondary oxidant;
• and
• (E) combusting secondary oxidant with unburned fuel to provide additional heat and combustion reaction products within the furnace.

A method for affecting the oxidation state of metal species comprising

• introducing into a furnace, which contains molten glass in a refining zone, at a point above the refining zone, fuel and primary oxidant,
• combusting fuel and primary oxidant within the furnace and above the refining zone and in an oxy-fuel burner in order to produce heat and combustion reaction products,
• introducing secondary oxidant into the furnace,
• establishing a fuel rich gas layer and a oxygen rich gas layer;
• and,
• exposing one of the gas layers to the molten glass under conditions sufficient to change the oxidative state of transition metal species in the molten glass.