Method of combusting nitrogen-containing fuels

The method of combusting nitrogen-containing carbonaceous fuel while suppressing formation of oxides of nitrogen from said nitrogen contained in the fuel, comprising:

• forming a first mixture of said fuel in intimate admixture with an amount of air substantially less than the amount needed for complete combustion of all the combustible components in said fuel but sufficient to support substantial combustion of said fuel;
• combusting said first mixture under essentially adiabatic conditions in a first combustion zone in the presence of a catalyst to form a first effluent, the combustion in said first combustion zone being characterized by said first mixture having an adiabatic flame temperature such that, upon contact with said catalyst, the operating temperature of said catalyst is substantially above the instantaneous auto-ignition temperature of said first mixture but below a temperature that would result in any substantial formation of oxides of nitrogen or other fixed nitrogen compounds from atmospheric nitrogen present in said mixture thereby effecting sustained combustion of a portion of said fuel at a rate surmounting the mass transfer limitation;
• mixing said first effluent eith an additional amount of air at least sufficient for complete combustion of all combustible components remaining in said first effluent to form a second mixture;
• and combusting said second mixture in a second combustion zone below a temperature that would result in any substantial formation of oxides of nitrogen from atmospheric nitrogen.