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.
Liquid metal irrigation of a packed bed
Abstract Liquid hold-up and gas phase pressure drop data are reported for mercury irrigation of a packed bed of 1 4 in. steel raschig rings with countercurrent flow of hydrogen and nitrogen. The static hold-up of mercury was found to decrease slightly with increasing liquid rates. This effect, not observed in aqueous or organic liquid irrigations, is attributed to an increased mobility of the liquid in the bed because of the greater energy associated with the flow of dense media such as a liquid metal. When nitrogen was the gas phase, the static hold-ups, dynamic hold-ups and irrigated liquid specific surfaces are all larger than those observed under comparable conditions with hydrogen as the gas phase. This is considered to be due to the greater interfacial tension of mercury and nitrogen. An empirical correlation is developed between the liquid hold-up, gas phase pressure drop, gas mass flow rate and gas density. It is suggested that this type of correlation would be of value for estimating the hold-up of molten metal or slag in high temperature systems, where direct measurement would be difficult, but where a room temperature analogue could be readily constructed.
Mechanics of vertical moving fluidized systems: II. Application to countercurrent operation
Experimental data are presented for two different methods of operating vertical moving fluidized systems of glass spheres and water: free countercurrent fluidization and bottom-restrained nonfed, or batch, fluidization. Data for a lead-shot-and-water system are also reported. A comparison is made of these data with a generalized theoretical analysis of ideal fluidized systems. The validity of a single characteristic holdup vs. slip-velocity relationship is illustrated, and consideration is also given to the prediction of flooding in the free countercurrent systems.