Low NOX burners are modified swirl burners that create a fuel-rich combustion zone followed by a leaner burnout zone. The degree of NOx reduction that can be achieved for a given coal is limited by the requirement to produce a stable flame and maintain adequate burnout.

These burners create a hot flame envelope around the fuel rich zone near the burner outlet.  This flame envelope promotes the devolatilisation of the coal which releases a greater amount of the coal nitrogen within this fuel rich region leading to lower NOx formation. As shown in the figure below these burners have improved NOx reduction and better flame stability characteristics than the conventional Low NOx burners. Examples of these burners are the CRIEPI's CI-α burner and Babcock & Wilcox (B&W) DRB-4Z burner.