Methods and apparatus for burning fuel with low NO.sub.x formation

An improved burner apparatus for discharging a mixture of fuel and air into a furnace space wherein said mixture is burned and flue gases having low NO.sub.x content are formed therefrom comprising:

• a housing having an open end attached to said furnace space;
• means for introducing a controlled quantity of air into said housing and into said furnace space;
• fuel jet mixer means for mixing fuel with flue gases from said furnace space and discharging the resulting mixture into the open end of said housing and into a primary reaction zone in said furnace space adjacent thereto, said fuel jet mixer means being attached to said housing and including a conduit for connection to a source of pressurized fuel having a fuel gas jet forming end, and at least one flue gases passageway communicating said fuel jet forming end of said conduit with flue gases in said furnace space and with the interior of said housing whereby flue gases from within said furnace space are drawn into said passageway, mixed with fuel and discharged into said housing;
• and
• at least one secondary fuel nozzle means attached to said housing for connection to a source of pressurized fuel and for introducing additional fuel into said furnace space.

A method of discharging an at least substantially stoichiometric mixture of fuel and air into a furnace space wherein said mixture is burned and flue gases having low NO.sub.x content are formed therefrom comprising the steps of:

• discharging said air into said furnace space;
• mixing a portion of said fuel with flue gases from said furnace space to form a fuel and flue gases mixture;
• discharging said fuel and flue gases mixture into said furnace space whereby said mixture combines with air and is burned in a primary reaction zone therein and flue gases having low NO.sub.x content are formed therefrom;
• and
• discharging the remaining portion of said fuel into a secondary reaction zone in said furnace space whereby said fuel mixes with flue gases and air contained in said furnace space and is burned in said secondary reaction zone.