Abstract
Gas-fluidized beds are commonly operated in a regime in which the rising particle-lean regions are dispersed in a 'continuous phase' of fluidized particles. The continuous phase is variously termed the dense, particulate, or emulsion phase, while the rising voids are termed bubbles if their diameter is less than that of the bed itself and slugs if their dimensions approach the diameter D or width of the containing column. Bubbling and slugging have been subjected to more research effort, experimental and theoretical, than any of the other regimes which have been recognized. The more important and useful findings are summarized.