Steady-State Crossflow Operation

Phase I flows through each stage in turn. Phase II is fresh feed to each separation stage. Within the stages, both phases are in cocurrent flow, with mass transfer from phase I into phase II. A mass balance over the first stage of the crossflow cascade, according to Eq. (1-178) and the notation in Fig. 1-64, gives 

The crossflow of phases in contact, as shown in Fig. 1-64, is used in thermal sepa- 

Loading or operating diagram for a steady-state cross-flow cascade consisting of three separation stages. 

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Alumina and other ceramic membranes of various microfiluaiion pore sizes have been used for the separation of yeast (saccharomyces cerevisiae) from the broth and the clarification of thin stillage [Cheryan, 1994]. A typical flux of 110 L/hr-m can be obtained with a crossflow velocity of 4 m/s and a transmembrane pressure of 1.7 bars. The crossflow velocity is found to markedly affect the membrane flux. Concenuation factors (ratios of final to initial concentrations) of 6 to 10 for both the broth and the stillage can be achieved. Backflushing with a frequency of every 5 minutes and a duration of 5 seconds helps maintain the flux, particularly in the initial operating period. The permeate flux for both types of separation reaches steady state after 30 to 90 minutes. 

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