OVERFIRE AIR INJECTOR AND FOSSIL FUEL COMBUSTION TYPE BOILER TO REDUCE EMISSION OF NITROGEN OXIDE BY IMPROVING MIXTURE OF AIR AND FLUE GAS

摘要

PURPOSE: An overfire air injector and a boiler are provided to improve the efficiency of an overfire air system by improving the mixture of air and flue gas. CONSTITUTION: An overfire air injector(44) is used in a fossil fuel combustion type boiler. The overfire air injector contains a cylindrical nozzle(45) having an outlet end(47) to contain a step-diffuser(46). The step-diffuser contains more than one radius steps(48) to expand the outlet end of the nozzle. A sprayer lance is installed inside the nozzle. A discharge orifice is installed in the outlet end to reduce a NOx emission by supplying a reducing agent in overfire air. Thereby, the mixture of air and flue gas is improved.