PRESSURE EFFECTS ON THE HYDRODYNAMIC BEHAVIOR OF GAS-LIQUID SOLID FLUIDIZED-BEDS

Basic hydrodynamic behavior of a gas-liquid-solid fluidized bed at elevated pressures up to 1 MPa was studied by measurement and visualization techniques in a specially constructed rectangular column. Conditions of gas and liquid velocities, particle size, distributor type, and pressure were varied in the apparatus, which was designed to allow operation in both two- and three-dimensional modes. Visualization in two-dimensional operation and measurement in three-dimensional operation were combined to provide a unique tie point between the two modes. The study indicated that bubble size decreases, bubble size distribution narrows, and gas holdup increases with increasing pressure. The type of distributor was found to have a marked impact on bed behavior, including bulk circulation, bubble coalescence, and gas holdup. Possible mechanisms for the observed pressure effects on the hydrodynamic behavior are also discussed, combined with available experimental observations. Analysis indicates that initial bubble size and maximum stable bubble size should decrease with increasing pressure due to changes in interfacial physical properties as well as in gas density.