Membrane systems design osmotic pressure

Some osmotic systems have been designed based on the principle that the semipermeable membrane will break open owing to osmotic pressure created by swelling of the osmagent to release the medicament. Time-controlled exploding systems (TES) were designed by Ueda et al.28... 

However, technological advances related to the development of new membranes operations and innovative strategies of process design, have partially overcome this limitation. Membrane distillation, for example, is not subject to osmotic-pressure limitation and can be therefore employed in integrated systems when high permeate recovery factors or retentate concentrations are requested. 

Brine Staging Velocity past the membrane is important. If too low, polarization is excessive, local O rises, and rejection declines. Fouling occurs faster. If too high, pressure losses are higher than they need be, and the osmotic pinch is premature. Since the volume of feed declines continuously, the hydraulic design needs periodic rearrangement. This is commonly done as shown in Fig. 22-64, sometimes known as a Christmas tree. This design is commonly used where the fluid is pumped once, as in RO, NF, and gas-separation systems, but not where recirculation is practiced, as in ultrafiltration. 

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