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[Waaayoff]

I am writing an optimization model for a seawater reverse osmosis plant. Everything seems to work fine except for a problem with my recovery rate which is optimized at 96.25%. Technically, the membrane has a maximum of 99.75% recovery rate. But I know that in reality the recovery rate is about 50% for seawater systems.

 

So my question is, what am I not including in my calculations that would limit my recovery to a reasonable value?

 

Could it be that my cost equations are wrong? I thought that: (high recovery = high pressure = high pumping cost), but apparently the cost actually decreases with high recovery. Because the pressure doesn't increase that much, while the feed mass flow rate is greatly reduced at higher recovery, lowering the cost.

 

Edit: I am not including any equations regarding fouling/scaling effects, nor do I have equations relating flux/permeability to feed temperature. But neither is the paper that I am following so...

Edited by Waaayoff, 11 April 2015 - 03:39 AM.