Patent ID: 6979430

Claim:
A method for controlling NO X emissions from a boiler that combusts carbonaceous fuels, the method comprising the steps of: (a) introducing carbonaceous fuel and combustion air into a furnace of the boiler for combusting the carbonaceous fuel in oxidizing conditions and producing flue gas that includes NO X and CO, and adjusting the operating conditions in the furnace so as to decrease the molar concentration of NO X and to increase the molar concentration of CO at the furnace exit such that the molar concentration of CO at the furnace exit is at least 70% the molar concentration of NO X ; and (b) leading flue gas from the furnace to a catalyst section in a flue gas channel for converting NO X to N 2 and CO to CO 2 by using CO as the reductant of NO X on a catalyst in the catalyst section, wherein no external reagent is introduced into the flue gas channel.