pressure effects on pervaporation 1

[ridge2481]

Dear All:

1) Does upstream pressure have any effect on pervaporation flux?

2) Will higher upstream pressure create higher driving force ?

Please let me know your suggestions.

Thanks
RW

 

[PVmem]

RW,
it doesn't as the driving force is the difference in partial pressures of the permeating components on feed and permeate side. And partial pressure of a component in a mixture is only depending on its composition (activity coefficients) and its temperature.
Therefore by either increasing the feed temperature and/or decreasing permeate pressure, the process can only be optimised. However there is an economic "lowest permeate pressure" vs. flux increase, either defined by the size of the vacuum pumps or coolant temperature required to maintain the permeate pressure.

Regards
mem

 

[ridge2481]

PVmem,

Thanks for the explaination. In my system, I am having a moderate upstream pressure (<25psi) that varies with the flow rate. I see flux value increasing with increase in flow rate i.e, inturn the upstream pressure. At that point i was thinking if this could be a pressure driven flow..Any comments or suggestions are welcome...
Also, I have few questions related to swelling of a polymeric membrane.

1) How do we know that if a membrane is swollen?
2) In another case, If I have a membrane that was swollen and then the entire pervaporation unit was shut down for a day or so..Now,Since the membrane is dry , How long would it take for this membrane to be swollen?

Thanks in advance,

RW