Hydrodynamics Characteristics and Gas-Liquid Mass Transfer in a Three Phase Fluidized Bed Reactor

Abstract

This paper presents the experimental characterization of hydrodynamics and gas-liquid mass transfer in a three-phase fluidized bed containing polystyrene and nylon particles. The influence of gas and liquid velocities on phase holdups and volumetric gas-liquid mass transfer coefficient was investigated for flow conditions similar to those applied in biotechnological process. The phase holdups were obtained by the pressure profile technique. The volumetric gas-liquid mass transfer coefficient was obtained adjusting the experimental concentration profiles of dissolved oxygen in the liquid phase with the predictions of the axial dispersion model. According to experimental results the liquid holdup increases with the gas velocity, whereas the solid holdup decreases. The gas holdup increases significantly with the increase in gas velocity, and it shows for the three-phase fluidized bed comparable values or larger than those of bubble column. The volumetric gas-liquid mass transfer coefficient increases significantly with an increase in the air velocity for both bubble column and fluidized beds. In addition, in the operational condition of high liquid velocity, the presence of low-density particles in the bed increased the gas-liquid mass transfer, and thus the volumetric mass transfer coefficient values obtained in the fluidized bed were comparable or larger than those of bubble column

Experimental and analysis study on dispersion of phases in an Ebullated Bed Reactor

“…Data in Table 4 were utilized to obtain an empirical correlation which connects the longitudinal dispersion coefficient with the studied operating parameters. Figure 9 shows a comparison in dispersion coefficient of present work with the published works of Kim and Kim (1983), and Silva (2001) who worked on three phase fluidized bed columns with air-water-solid particles systems. For Figure 9, the operating conditions used by Kim and Kim (1983) are liquid velocity (u Lo = 2 cm/s), gas velocity (u G = 0-8 cm/s), glass particle size (1.7 mm) and column diameter (14.5 cm) while that used by Silva (2001) are liquid velocity (u Lo = 1.3 cm/s), gas velocity (u G = 0-2.4 cm/s), polystyrene particle size (2.2 mm) and column diameter (6.3 cm).…”