Patent ID: 7467943

Claim:
A method for combusting fuel in a fired heater having one or more burners, the method comprising: (a) combusting at least a portion of said fuel in the presence of an oxygen-containing oxidizer in said burners, generating heat and producing a flame and a flue gas; and (b) recycling at least a portion of said flue gas to said burners; wherein step (a) and step (b) are conducted in a manner such that combusting takes place in a combustion regime represented by 4 ⁢ , ⁢ 500 ≥ 7554.8 - 933.72 ⁢ x + 64.960 ⁢ x 2 + .47705 ⁢ y - .55680 ⁢ z - 1579.2 w ≥ 2 ⁢ , ⁢ 500 ; wherein w represents a mole fraction of oxygen in the oxidizer; wherein x represents a recycle ratio of said flue gas as measured in moles of flue gas/mole of oxidizer; wherein y represents a temperature of the flue gas, in Fahrenheit, recycled to said burners; and wherein z represents a heating value of said fuel in Btu/scf LHV.