Pilot nozzle steam injection for reduced NO.sub.x emissions, and method

A combustion system comprising:

• a diffusion flame pilot assembly having a fuel line with a downstream end terminating at a pilot nozzle;
• a steam delivery assembly having a steam line terminating at a steam outlet proximate to said fuel line and upstream of said pilot nozzle;
• a nozzle block comprising:
• upstream and downstream surfaces;
• and
• a bore surface extending between said upstream and downstream surfaces defining a steam line bore through which said steam line extends, wherein said pilot nozzle and said steam outlet are downstream of said nozzle block;
• and
• wherein:
• a) said steam line has an outside surface and an outside diameter;
• b) said steam line bore has a bore diameter greater than said steam line outside diameter;
• and
• c) said steam line bore surface and said steam line outside surface define an annular air gap.

A combustion system comprising:

• a diffusion flame pilot assembly having a fuel line with a downstream end terminating at a pilot nozzle;
• steam delivery means for injecting a steam flow toward said pilot nozzle;
• wherein said steam delivery means comprises means for splitting said steam flow into a plurality of individual steam streams and passing such streams through a plurality of locations around said fuel line, respectively;
• a nozzle block comprising upstream and downstream surfaces, wherein said pilot nozzle is downstream of said downstream surface, and said steam delivery means comprises steam line means for enabling said steam flow to pass through said nozzle block from said upstream surface to said downstream surface;
• and
• wherein said steam delivery means comprises insulation means for inhibiting thermal gradients in a region of said nozzle block proximate to said steam line.

A combustion method for reducing NO.sub.X emissions out of a combustion system comprising the steps of:

• enabling a pilot fuel stream to flow through a fuel line in a downstream direction and out a diffusion flame pilot nozzle;
• directing a steam flow downstream toward said pilot nozzle;
• wherein said directing said steam flow step further comprises the step of splitting said steam flow into a plurality of individual steam streams and passing such streams through a plurality of locations around said fuel line, respectively;
• and
• wherein said enabling said steam flow to split step further comprises the step of directing said steam flow into an inlet of a steam injection toroid disposed about said fuel line and upstream of said pilot nozzle, said steam injection toroid having a plurality of steam injection ports directed toward said pilot nozzle and away from said fuel line.