PREDICTION OF LIMITING FLUX IN ULTRAFILTRATION OF KRAFT BLACK LIQUOR

Ultrafiltration of black liquor was carried out using an asymmetric membrane in a stirred batch cell, modified to work on a continuous mode. Poly (ethylene glycol)-6000 was used as a standard macromolecule to compare the results. An attempt was made to predict the flux using a generalized formulation which takes into account the unsteady-state behaviour during the initial stages of continuous stirred ultrafiltration. The model combines film theory, gel theory and filtration theory to predict permeate flux as a function of time. The governing partial differential equation, based on the unsteady-state mass balance concept, was solved numerically. The predicted flux values were compared with experimental data and the average deviations were found to be less than 7%.