Abstract
In a fluidized bed with a draft tube, solid particles can be smoothly circulated by keeping the inner zone within the draft tube in a fluidized condition and the outer annular zone between the draft tube and the column wall in a fixed-bed condition. The size of the opening under the draft tube was found to be quite important in achieving smooth and steady circulation. When it was too small, solids circulation was retarded or entirely stopped.
To elucidate the driving force of this solids circulation, a fluidized bed and a fixed bed were connected through an opening and the equilibrium conditions between the heights of both beds were examined experimentally and theoretically. The concept of the equilibrium bed heights proposed in this study can be applied not only to problems of the circulation of solid particles but also to similar problems in the solids handling, such as the elevation of solids.
