On the basic hydrodynamics of inverse liquid-solid circulating fluidized bed downer

A new type of fluidized bed called Inverse Liquid-Solid Circulating Fluidized Bed (ILSCFB) has been developed. The circulating fluidized bed consists of the downer with an inner diameter of 7.6 cm and the height of 5.4 m, upcomer with an inner diameter of 20 cm, separator, and connecting pipes between the downer to the storage column. The operation window has been demonstrated at different solids circulation rate and liquid velocity. The hydrodynamic characteristics in the downer of ILSCFB are investigated experimentally by fluidization of the styrofoam and Hollow Glassbeads whose densities are smaller than that of the fluidization media. Average solids holdup in the downer is measured where different liquid velocity and different solids circulation rate in terms of superficial solids velocity. For both types of particles, axial solids holdup distribution is quite uniform under various operating conditions, while radial solids holdup distributions are slightly non-uniform with a minor increase in solids holdup adjacent to the wall under various operating conditions, but no obvious "core-annulus" structure is observed. The comparisons of the hydrodynamics in the ILSCFB and Liquid-Solid Circulating Fluidized Bed (LSCFB) are also made based on the single particle force balance discussion, enabling the generalization of inverse and upwards circulating fluidization of particles. (C) 2019 Elsevier B.V. All rights reserved.