System and method for reduced NOx combustion

A method for reducing NOx pollutants in the combustion of hydrocarbon fuels in a two stage furnace which provides for internal flue gas recirculation, said method comprising:

• establishing and maintaining a first stage of combustion and passing a stream of combustion air and first stage products of combustion to down a centerline of the burner to a second stage;
• and
• establishing a second stage of combustion downstream from the first stage of combustion and concentrically disposed about and open to the first stage, establishing the second stage further comprising:
• arranging an array of fuel tips around the first stage burner, each fuel tip having a fuel jet with a nominal trajectory angled toward the centerline of the burner and a high pressure steam port placed between the burner and the fuel jet which is nominally angled to cross the nominal trajectory of the fuel jet;
• injecting fuel through the fuel jet into the burner;
• injecting high pressure steam through the steam port such that it influences the trajectory of the fuel to a modified fuel trajectory which is moved away from the centerline of the burner;
• and
• controlling the injection of the steam as a function of function of firing rate for the burner such that the modified fuel trajectory is moved progressively outward from the centerline of the burner across a range of increasingly higher firing rates.

A low NOx burner comprising:

• a burner housing providing for internal flue gas recirculation;
• a primary stage burner having a centerline and an outlet within the furnace housing;
• a secondary stage burner system comprising:
• a plurality of second stage fuel tips forming a concentric array around the centerline and slightly upstream of the primary stage burner, each secondary stage fuel tip comprising:
• a fuel jet having a initial trajectory for the fuel which is angled toward the primary stage burner;
• and
• an inert gas jet between the fuel jet and the primary stage burner and having a normal trajectory for the inert gas which intersects the initial trajectory for the fuel;
• whereby inert gas injected through the inert gas jets of the secondary stage fuel tips influences the trajectory of the fuel to a modified fuel trajectory which is moved away from the centerline of the burner.

A multiple stage furnace for burning a fuel in a low NOx combustion utilizing steam, said furnace comprising:

• a burner having a centerline;
• and
• a second stage fuel tip comprising:
• a fuel tip housing having a longitudinal axis;
• a fuel jet at the end of the fuel tip housing and disposed to inject fuel along a first nominal trajectory at an angle to the burner centerline;
• a fuel conduit within the fuel tip housing communicating with the fuel jet;
• a high pressure steam port disposed to inject steam at a second nominal trajectory, said second nominal trajectory intersecting the first nominal trajectory;
• and
• a steam supply tube within the fuel tip housing communicating with the high pressure steam port;
• whereby the fuel tip is disposed to transfer momentum from the steam expelled through the high pressure steam port to fuel injected into the furnace through the fuel jet, thereby creating a combined trajectory carrying fuel into the furnace at an angle different than the first nominal trajectory established by the fuel jet.