Coanda gas burner apparatus and methods

A method of burning a mixture of air, fuel gas and flue gas in a furnace space of a furnace to generate heat in the furnace space wherein a gas burner apparatus including a wall surrounding a mixing zone for mixing the air, fuel gas and flue gas prior to combustion thereof is utilized, comprising:

• providing a Coanda surface on the exterior surface of the wall of the burner apparatus;
• injecting primary fuel gas into the mixing zone in a manner that causes the fuel gas to mix with air in the mixing zone;
• discharging the mixture of air and fuel gas from the mixing zone;
• burning the mixture of air and fuel gas discharged from the mixing zone in a primary reaction zone in the furnace space;
• injecting a stream of secondary stage fuel gas on or adjacent to the external Coanda surface in a manner that entrains flue gas into the stream to create a secondary fuel gas/flue gas mixture and causes such secondary fuel gas/flue gas mixture to burn in a secondary reaction zone in the furnace space.

A method of burning a mixture of air, fuel gas and flue gas in a furnace space of a furnace to generate heat in the furnace space wherein a gas burner apparatus including a wall surrounding a mixing zone for mixing the air, fuel gas and flue gas prior to combustion thereof is utilized, comprising:

• providing a pre-mix membrane in said mixing zone, said pre-mix membrane extending around the interior surface of said wall and the perimeter of said mixing zone;
• discharging a mixture of fuel gas and air from said pre-mix membrane around the perimeter of said mixing zone;
• igniting said mixture of fuel gas and air discharged from said pre-mix membrane around the perimeter of said mixing zone;
• injecting primary fuel gas into said mixing zone from a primary fuel gas injection assembly separate from said pre-mix unit in a manner that entrains flue gas from outside said mixing zone into said mixing zone and causes said flue gas to mix with air and fuel gas in said mixing zone;
• using said ignited mixture of fuel gas and air discharged from said pre-mix membrane around the perimeter of said mixing zone to ignite the mixture of primary fuel gas, flue gas and air formed by injecting primary fuel gas into said mixing zone from said primary fuel gas injection assembly;
• discharging said mixture of air, fuel gas and flue gas from said mixing zone into said furnace space;
• and
• burning said mixture of combustion air, fuel gas and flue gas discharged from said mixing zone in said furnace space.