Low-NO.sub.x staged combustion device for controlled radiative heating in high temperature furnaces

A staged oxy-fuel combustor system comprising in combination:

• an oxy-fuel burner having a housing having a first end and a flame end, said housing having a cross-sectional shape with a width and height of different dimensions, a fuel conduit having a first end and a nozzle end disposed in spaced relation to and concentrically within said housing, said fuel conduit having a cross-sectional shape complementary to that of said housing thus defining a passage between said fuel conduit and said housing, said fuel nozzle having a width to height ratio of between 2 and 60;
• a precombustor mounted on said burner, said precombustor having a first central passage complementary to and of a width and height equal to or larger than the width and height of said burner housing said precombustor having a first end in fluid tight relation to the flame end of said housing and a second end adapted to direct said flame produced by said burner for heating in industrial environments, the longitudinal axis of said precombustor being an extension of the longitudinal axis of said housing of said burner, a second separate passage disposed beneath and coextensive with said first central passage said second passage having a nozzle end terminating in said second end of said precombustor passage and nozzle adapted to direct a fluid underneath and generally parallel to said flame, said precombustor having a length of from 1 to 24 inches;
• and
• means to introduce fuel into said fuel conduit of said burner and an oxidizer into said passage defined by said housing and said nozzle conduit, and staging means to introduce an oxidizer into said second separate passage in said precombustor whereby a fuel rich oxy-fuel flame overlays a highly radiative fuel lean flame beyond the flame end of said precombustor.