Hydrodynamic Performance of a Novel Design of Pressurized Fluidized Bed Combustor

A bench-scale fluidized bed combustor with a novel fluidizing gas injection manifold was successfully built for characterization of Australian black coals under PFBC conditions. Instead of the usual horizontal distributor plate to support the bed and distribute the fluidizing gas, the fluidizing gas was injected horizontally through 8 radial ports in the cylindrical wall of the combustor. To verify satisfactory hydrodynamic performance with the novel gas injection manifold, the fluidization was directly investigated by measuring differential pressure fluctuations under both ambient and PFBC conditions. In addition, a Perspex cold model was built to simulate the hydrodynamics of the hot bed in the PFBC facility. Under PFBC conditions, the bed operated in a stable bubbling regime and the solids were well mixed. The bubbles in the bed were effectively cloudless and no gas backmixing or slugging occurred; so the gas flow in the bed could be modeled by assuming two phases with plug flow through each phase. The ratio of Umf for the simulated bed to Umf for the hot PFBC bed matched the conditions proposed by Glicksman’s scaling laws. The bubbles rose along the bed with axial and lateral movements, and erupted from the bed surface evenly and randomly at different locations. Two patterns of particle movement were observed in the cold model bed: a circular pattern near the top section and a rising and falling pattern dominating in the lower section.