Hydrodynamic studies on three-phase external loop airlift fluidized bed

Abstract

Large numbers of industrial process reactions are involved in the simultaneous contacting of gas, liquid and solid. These operations are carried out in the multiphase reactors. In the three phase operations, the solid particles are added either as a catalyst or an inert material to increase the mixing characteristics of liquid phase reactants and gaseous phase reactants. The airlift fluidized bed reactors are divided into two sections, the riser and the down comer, depending on the arrangement of the down comer, classified into the internal-loop or external loop airlift reactors. The external loop airlift fluidized bed reactor provides an excellent contact among the various phases, easy removal or replenishment of the particles, reasonable interface mass transfer rates with low energy input and easier scale up. In this present study, experiments have been carried out to analyse the influence of superficial liquid phase velocity, gaseous phase velocity, dimensions of the particles and physical properties of the liquid on the above mentioned hydrodynamic parameters. Also the unified dimensionless correlations were developed to estimate the minimum fluidization velocity, riser gas holdup, riser liquid holdup and liquid circulation velocity by using both the Newtonian and the non Newtonian systems in a three-phase external loop airlift reactor. The experimental results showed a good conformity with those predicted correlations according to the developed correlation. The proposed correlations for the prediction of the minimum fluidization velocity, riser gas holdup, riser liquid holdup and liquid circulation velocity in an external loop airlift reactor were found to be satisfactory for both the Newtonian and non-Newtonian systems with a wide range of variables covered in the present investigation.