Membranes external mass balances

The selectivity should be greater than 20 to accomplish significant separation of species / from species j. For a completely mixed membrane system, the external mass balance yields... 

The RT Eq. tl7-21i needs to be solved simultaneously with an expression for the mass balance. We will again assume the membrane module is well mixed. The module is identical to Figure 17-6A except the y terms are replaced by liquid wt frac. The external mass balances for this well-mixed module (in mass units) are... 

On shell fiiquidl side. Mass balances for species A and B in the bulk liquid now relate the net rate of material loss to the flux integrated over the external surface of the membrane tube ... 

Consider separation of a binary mixture in a membrane module with the crossflow pattern shown in Figure 9.3. The feed passes across the upstream membrane surface in plug flow with no longitudinal mixing. The pressure ratio and the ideal separation factor are assumed to remain constant. Film mass-transfer resistances external to the membrane are assumed to be negligible. A total mass balance around the differential-volume element gives... 

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