An apparatus and method is presented for reducing mono nitrogen oxide emissions in a hydrocarbon processing furnace. A preferred embodiment hydrocarbon cracking furnace includes a firebox with a set of wall burners and a set of floor burners, the floor burners comprising secondary burner tips burning a fuel-rich mixture and positioned below primary burner tips burning a fuel-lean mixture. A portion of flue gases are recirculated from the primary burner combustion area to the secondary burner combustion area and back to the primary burner combustion area. The floor burners further comprise a set of steam injection ports that inject steam into a conical flow to contact flames at the primary burner tips, reducing flame temperature and thereby reducing thermal NOx. The steam injection ports are positioned in the firebox above the primary burner tips.