Low emissions burner with premix flame stabilized by a diffusion flame

A low emissions burner comprising:

• a diffusion burner including a casing for receiving air under pressure and having an axis, a swirler for mixing and imparting rotational motion to the air supplied through said casing and a fuel inlet to said casing for providing a stabilized flame downstream of the swirler;
• a plurality of discrete premix burners surrounding said air supply casing about said axis;
• each said premix burner including a chamber, a fuel supply conduit for supplying fuel into the chamber and an air supply conduit for supplying air under pressure into said chamber;
• said conduits terminating in outlet ports enabling premixing of the air and fuel supplied to the chamber via said conduits and providing a substantially premix annular flame downstream of said premix burners surrounding the stabilized flame of the diffusion burner;
• and
• a water injection nozzle for said diffusion burner for injecting water into the stabilized flame of the diffusion burner to cool the core of the diffusion flame and reduce NOx production.

In a low emissions burner having a central diffusion burner including a casing for receiving high pressure air, an inlet for supplying fuel to the casing and swirl blades for swirling the air and fuel and an array of premix burners surrounding the diffusion burner each including a burner sleeve, a fuel conduit for supplying fuel to the burner sleeve and a high pressure air conduit for supplying high pressure air into the burner sleeve for premixing with the fuel, a method of operating the burner comprising the steps of:

• maintaining a stabilized diffusion flame by maximizing the high pressure air supplied to said casing and maintaining a constant fuel flow rate to the diffusion burner;
• stabilizing the premix flame using the diffuser flame;
• and
• modulating the flow of fuel to the premix burners while maintaining constant the flow of fuel to the diffusion burner.