Patent ID: 6881053

Claim:
A pre-mix burner for the combustion of fuel in a furnace, said burner comprising: (a) a burner tube having an upstream end, a downstream end and a venturi intermediate said upstream and downstream ends, said venturi including a throat portion having substantially constant internal cross-sectional dimensions such that the ratio of the length to maximum internal cross-sectional dimension of said throat portion is from about 6.5 to about 7.5; (b) a burner tip mounted on the downstream end of said burner tube adjacent a first opening in the furnace, so that combustion of the fuel takes place downstream of said burner tip; (c) a gas spud located adjacent the upstream end of said burner tube, for introducing fuel into said burner tube, said fuel flowing from said upstream end through said venturi to said downstream end; and (d) at least one passageway having a first end in fluid communication with a source flue gas and a second end adjacent the upstream end of the burner tube, flue gas being drawn from said furnace through said passageway in response to the inspirating effect of the fuel flowing though said venturi, wherein flue gas alone is mixed with fuel at the upstream end of said burner tube.