Simultaneous Reduction of SO2, NOx, and N2O Emissions from a Two-Stage Bubbling Fluidized Bed Combustor

The effect of limestone feed during bubbling fluidized bed combustion of coal on emissions of SO2, NOx and N2O was investigated. Two types of bubbling fluidized bed combustors (BFBCs) were employed; One was a conventional single-stage BFBC in which limestone was fed to the bed where coal was burnt, and the other was a two-stage BFBC in which coal was burnt in the lower bed and the desulfurization of the flue gas from the lower bed was conducted in the upper bed. For the single-stage BFBC, limestone feed into the bed decreased SO2 and N2O emissions but it increased NOx emission. The two-stage BFBC was found to decrease SO2 and N2O emissions without increasing NOx emission. The results of SO2 capture and N2O reduction in the upper bed of two-stage BFBC were analyzed using Kunii-Levenspiel model. The results of the calculation agreed fairly well with the experimental results.