FURTHER-STUDIES OF THE REGIMES OF FLUIDIZATION

As the velocity of a gas flowing across a bubbling fluidized bed is slowly raised, the heterogeneous structure of the bed first peaks, then changes gradually to a condition of increasing uniformity culminating in the turbulent state where on the whole large discrete bubbles or voids are absent. The turbulent regime extends to the transport velocity, beyond which solid fed to the bottom of a vertical vessel traverses it in fully entrained flow and the concentration of the resulting suspension depends not only on the velocity of the gas but also on the solid flow rate. If the solid rate is low, dilute-phase flow results; if the solid rate is sufficiently high, then it is possible to maintain in the vessel a high solid concentration typical of the fast fluidized bed. This paper presents data, obtained with several solids in cold model rigs, which serve to delineate the fluidization regimes noted above and their boundaries. The results also throw light on the phenomenon of choking. © 1979.