Prediction of Riser Gas Holdup in Three- Phase External Loop Air Lift Fluidized Bed Reactor

Hydrodynamics is an important issue for design and development of three phase external-loop airlift fluidized bed. This paper deals on the experimental investigations on the effect of superficial gas and liquid velocities and properties of solids on the riser gas holdup of a three phase external-loop airlift fluidized bed reactor and it was characterized using Newtonian and non Newtonian systems. Water, 65% and 85% of glycerol and n-butanol were used as Newtonian liquids and different concentration of Carboxyl Methyl Cellulose (CMC) i.e., 0.2%, 0.5% and 1% were used as non Newtonian liquids. Spherical glass beads, bearl saddles and rasching rings of different sizes were used as solid phase. The phase flow rates and properties of solid particle had significant effect on the hydrodynamic characteristics of the external-loop airlift fluidized bed reactor such as riser gas holdup. Unified correlations have been developed to estimate the riser gas holdup as a function of superficial phase velocities, properties of solid particle and physical properties of both Newtonian and Non-Newtonian liquid systems. The predicting ability of the correlations were tested with the experimental data and found to be good fit with an absolute average relative error (AARD) of ± 9.7 % for riser gas holdup.