Hydrodynamic behaviour of a gas—solid counter-current packed column at trickle flow
Trickle flow of a more or less fluidized catalyst through a packed column is a promising new gas—solid counter-current operation. The hydrodynamic, behaviour of such a column, filled with dumped PALL rings, has been investigated, while some results have been obtained with RASCHIG rings and cylindrical screens as packing. The solid used was a microspherical catalyst carrier. Pressure drop, hold-up, loading and flooding were evaluated and compared with literature data for gas—liquid systems. The behaviour is analogous although the absolute magnitude is different. 
 
Pressure drop is low, up to 50% of the solid being carried by the packing. A correlation for the pressure drop, which is mainly caused by suspended particles, has been derived. At low gas velocities particle velocity is constant, whilst near flooding the slip velocity between gas and solid reaches a constant value. Using empirical values for particle velocity and slip velocity, hold-up, loading and flooding can be predicted. Scaling-up problems still need to be investigated. Results on mass transfer, axial dispersion of both phases and solid spread factors will be published later.
On flooding in packed columns
A mechanism for flooding in packed columns, based on interactions between holdup and pressure gradient is proposed and is shown to be consistent with experimental observations. The differences in the flooding mechanism between wetted wall columns and packed columns are considered also.
THE PROPERTIES OF BUBBLES IN FLUIDIZED BEDS OF CONDUCTING PARTICLES AS MEASURED BY AN ELECTRORESISTIVITY PROBE
Abstract An electroresistivity probe was used to determine point properties of an air-fluidized bed of conducting coke particles. The probe contained two electrodes, one vertically above the other and separated by a known distance. Interruptions of current between the electrodes of the probe and a large wall electrode were analyzed with the aid of a hybrid computer to yield information on bubble properties (frequency, volume fraction, size and size distribution and rising velocity) as a function of fluidization level, particle size and position within the bed. The results are generally in agreement with available theory and literature data.