Abstract
Mitsubishi Heavy Industries. Ltd. has been developing the biomass fired bubbling fluidized bed boiler in recent years. The problem with regard to the gas emissions is that the simultaneous control of CO, NOx and dioxins is difficult, which is to say that on one hand CO and dioxins reduces in oxidized region with high temperature in freeboard, on the other hand NOx lowers in reducing region in bed. In order to reduce CO, NOx and dioxins simultaneously the air for the fuel combustion is separately fed into the furnace with four-staged air. The fluidized bed is maintained reducing zone in order to reduce NOx emission. The gas temperature rises with the secondary air injection for less CO and dioxins emissions. As a result of the boiler performance test, the emission levels of CO, NOx and dioxins are below the targeted values respectively in a satisfactory way.
