Patent ID: 7569200
Filing Date: 2009-08-04
Classification: B01D,D21C,F23C,F23G,F23J

Abstract:
1. Method of reducing the amount of nitrogen oxides present in flue gases which result from the combustion of fuels with air, the method comprising sequentially: (a) combusting fuel in a first zone to form a combustion gas containing nitrogen oxides; (b) adding additional fuel in a second zone located downstream of the first zone in which reducing conditions prevail and controlling the temperature and time of the combustion gas in the second zone so that the nitrogen oxides therein are preferentially and substantially converted to hydrogen cyanide (HCN) which thereby causes HCN to accumulate in the second zone, and thereafter (c) feeding air at at least two levels in a third zone located downstream of the second zone in order to generate conditions for final oxidation of combustibles and conversion of the HCN in the combustion gas from the second zone substantially to N2.