Combustion system with reduced nitrogen oxide emissions

A combustion system 200 having reduced nitrogen oxide emissions is presented. The combustion system includes a combustion zone 220, which includes a burner for converting a fuel, under fuel rich conditions, to a flue gas. An intermediate staged air inlet 232 is situated downstream from the combustion zone, for supplying intermediate staged air to the flue gas and producing fuel lean conditions. A reburn zone 224 is located downstream from the intermediate staged air inlet for receiving the flue gas. Preferably, the combustion zone comprises two or more burners arranged in two or more rows. The intermediate staged air may be supplied as boosted air. Preferably, an overfire air inlet 236 is provided for supplying overfire air to a burnout zone 226 downstream from the reburn zone. The combustion system may include a boiler nose tip 240 through which the flue gas flows. In further aspects, a process for using the combustion system and a method of reducing NOx flowing into the reburn zone of the combustion system are also described.