Behavior of gas-solid mixtures in a moving bed downcomer with an orifice under negative pressure gradient

摘要

Flow characteristics of gas-solid mixtures in a moving bed downcomer operating under negative pressure gradient are important factors in powder handling processes, such as multi-stage spouted beds or circulating fluidized bed. Based on experimental observation, the moving bed flow changed from smooth flow (Region(Ⅰ)) to slip-stick flow (Region( Ⅱ)), to intermittent flow (Region(Ⅲ)) as the gas pressure at the bottom of the downcomer was increased. In this study, the critical point for steady-state operation (Region(Ⅰ)) was investigated experimentally and theoretically by using eight kinds of solid particles (Geldart B, D and A powders) and also six different orifice sizes were used to restrict solids flow at the base of the downcomer.