Patent ID: 6866502

Claim:
A system for reducing NO x emissions in the combustion of fuel comprising: (a) a furnace having at least one burner, said at least one burner comprising: (i) a primary air chamber; (ii) a burner tube including a downstream end, an upstream end in fluid communication with said primary air chamber for receiving air, flue gas or mixtures thereof and fuel, a venturi portion positioned between said downstream end and said upstream end, and a burner tip mounted on the downstream end of said burner tube for combusting fuel downstream of said burner tip; and (iii) a fuel orifice located adjacent the upstream end of said burner tube for introducing fuel into said burner tube; (b) a source of flue gas, said source positioned so as to enable the flue gas to achieve a temperature of less than 2000° F.; (c) at least one passageway for conducting flue gas from said source to said primary air chamber; and (d) inspirating means positioned within said at least one burner, said inspirating means including said venturi portion effective for drawing flue gas from said source, through said at least one passageway and said primary air chamber in response to an inspirating effect of uncombusted fuel exiting said fuel orifice, the uncombusted fuel flowing through said burner tube from its upstream end towards its downstream end, whereby the flue gas is mixed with air and fuel at said upstream end of said burner tube prior to the zone of combustion of the fuel.