ANALYSIS OF THE FOULING MECHANISM IN MICROFILTRATION OF ORANGE JUICE

The purpose of this work is theoretical and experimental evaluation of fouling effects on flux performance in clarification of freshly squee zed orange juice by cross-flow microfiltration. To identify optimum op erating conditions to minimize fouling effects, juice was microfiltere d on a laboratory scale plant varying axial velocity and transmembrane pressure difference. The observed flux decay was modeled using a modi fied form of the differential equation used to describe classical dead -end filtration processes. The mechanism of fouling during cross-flow microfiltration was identified by estimation of the model parameters a ccording to a nonlinear regression optimization procedure. Analysis of the results revealed that the separation process is controlled by a c ake filtration fouling mechanism as the juice is fed at relatively low velocity (i.e., Re = 5000) and the system is operated at low transmem brane pressure difference. In these operating conditions the permeate flux decays within the first 20-30 min to gradually achieve a limit va lue. At higher Reynolds number (Re = 15,000), an increase in applied t ransmembrane pressure (i.e., from 0.3 to 1 bar) allows the limit perme ate flux to increase by a factor of about 4. In these conditions the f iltration process is controlled by a complete pore blocking fouling me chanism, and the permeate flux becomes approximately invariant with re spect to time, and a negligible decay may be observed. Evaluation of s pecific energy consumption involved in the filtration process is repor ted.