Oil / Water Separation, Stokes Law & Demulsifier Chemical

[ChemEngSquirrel]

If I size my three phase separator using Stokes law to determine bulk liquids handling capacity (by determinig a separation area from the Stokes Law settling velocity), can i reduce separator size by giving credit to the fact that demulsifier chemical will improve separation (provided oil / water residence time are both acceptable)?

This is based on my understanding that Stokes Law for oil / water separation is conservative as it estimates separation area without the assistance of demulsifier chemical.

Thanks.

 

[shahyar]

Your 3-phase separator seperates the "free oil". A demulsifier breaks the emulsion to convert the "attached" oil droplets to free oil droplets. So, adding demulsifier doesn't justify you to give the credit.

 

[mfelzien]

Do not derate your vessel based upon there always being a supply of demulsfier. Often the supply of demulsfier runs out before the feed into your separator. And once you've sized the vessel, its sized.