The effect of superficial gas and liquid velocities and properties of solids on the minimum fluidization velocity and riser liquid holdup of a three-phase external loop air lift fluidized bed reactor was characterized using Newtonian and non-Newtonian systems. Water, 65% and 85% of glycerol and n-Butanol were used as Newtonian liquids and different concentrations of carboxymethyl cellulose (i.e. 0.2%, 0.5% and 1% CMC) were used as non-Newtonian liquids. Spherical glass beads, bearl saddles and rasching rings of different sizes were used as solid phases. The phase flow rates and properties of solid particles had significant effects on the hydrodynamic characteristics of the external loop air lift fluidized bed reactor, such as minimum fluidization velocity and riser liquid holdup. Unified correlations have been developed to estimate the minimum fluidization velocity and riser liquid holdup as a function of superficial phase velocities, properties of solid particles 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 a good fit with an absolute average relative deviation (AARD) of ± 6.5 % and ± 7.8 % for minimum fluidization velocity and riser liquid holdup, respectively.
Prediction of Riser Gas Holdup in Three- Phase External Loop Air Lift Fluidized Bed Reactor