Water-tube boiler with re-circulation means

摘要

The water-tube boiler fulfills the reduction in NOx with a simple constitution, and achieves reduction in NOx and reduction in CO at the same time with a simple constitution. In the water-tube boiler, a plurality of water tubes (5) are arranged in a zone where burning-reaction ongoing gas derived from a burner (10) is present within a combustion chamber (9), and exhaust gas recirculation equipment (26) is provided to feed part of exhaust gas exhausted from the combustion chamber 9 to the burner 10.