Emission of nitrogen oxides in a vortexing fluidized bed combustor

This study investigated experimentally the effects of fuel types and operating conditions on NO emission in a 0.45 m I.D. pilot scale vortexing fluidized bed combustor. Rice husk, soybean, high and low sulfur subbituminous coals, and bituminous coal were used as fuels. Silica sand was employed as the bed material. The effects of various operating conditions, such as bed temperature, excess air ratio, and stoichiometric air flow rate on NO emission were investigated. The dependence of the conversion of fuel-N on O/N and H/N weight ratios of the fuel was explored to understand the effect of fuel composition on NO emissions. The results show that the H/N ratio is a better indicator than the O/N ratio to represent the conversion of fuel-N to NO. Soybean was mixed with other fuels to study its characteristics for reducing NO emission. Taguchi method was applied to analyze the priority of operating conditions for dominating NO emission. It is found that the excess air is the most important factor to dominate NO emission.