Hydrodynamic study of fixed beds with cocurrent upflow and downflow

The performance of trickle bed reactor was studied by comparing the two modes of operation: cocurrent upflow and downflow of gas and liquid. The three important hydrodynamic parameters, two-phase pressure drop, total liquid holdup and axial dispersion were studied and the results for both modes of operation were compared. It was found that the two-phase pressure drop and total liquid holdup are higher for the upflow mode of operation at lower gas and liquid velocities, but with increasing flow rates, the two parameters were comparable for upflow and downflow modes. The values of Peclet number were higher in downflow mode of operation for the entire range of flow rates studied indicating the presence of lower backmixing in the downflow mode of operation. A comparison of the experimental observation with the correlations available in literature is presented. Correlations for estimating total liquid holdup and Peclet number (based on regression analysis) have been proposed.