Flue gas external circulation nitrogen reduction system

The utility model belongs to the technical field of flue gas emission reduction treatment, and particularly relates to a flue gas external circulation nitrogen reduction system. The flue gas external circulation nitrogen reduction system comprises a pyrolyzing furnace and a combustion chamber provided with a combustor, the combustor is communicated with a combustion-supporting air pipeline, high-temperature flue gas generated by the combustion chamber is communicated with a heating cavity of the pyrolyzing furnace, a first external circulation loop and a second external circulation loop are arranged between the heating cavity and the combustion chamber, the first external circulation loop is communicated with the combustion-supporting air pipeline, and the second external circulation loop is communicated with the combustion-supporting air pipeline. The second outer circulation loop directly communicates with the interior of the combustion chamber. Due to the arrangement of the two outer circulation loops, the