After-air nozzle for two-stage combustion boiler, and a two-stage combustion boiler, boiler and combustion method using the same

摘要

An after-air nozzle capable of reducing NOx and CO and a boiler equipped with such a nozzle are provided The after-air nozzle has a vena contracta such that an outside diameter of a flow passage diminishes towards the air-jetting port which supplies air to a boiler, and a changing apparatus changes a flow passage cross-sectional area of the vena contracta. A method of use of such an after-air nozzle and a boiler so equipped is also provided.