Is it possible to design for a continuous gravity separator and would such a system achieve an effective separation. How is the residence time for a typical API gravity separator derived. pls help

In refineries, there are many continuous gravity separators. The basic premise is to allow sufficient residence time for an oil droplet to rise to the surface of the API separator. You use Stoke's law to calculate the rate of rise of the oil droplet from the bottom of the separator to the top, where it can be skimmed off. You have to assume a droplet size, typically 150 microns is assumed. Using the flow rate of your inlet stream, you then calculate the residence time. The outlet oil is normally 50-100 ppm.

I did a quick search on Google and there are many references on how to do this. If you are not in the United States, go to www.google.com. Look for a link that says "Google in English". Follow this link. Use as your search parameters: oil droplet size API separator design. I even found an Excel spreadsheet for doing the sizing calculations.

ACS -Amistco offeres media for oil water separation.

Why cant you guys use a centrifuge. Could be set up to use it in a continuous system.

I have seen good experience with Vortoil hydroclone separators. However, gravity separation will normally be the least expensive method of separation.

it's common the need of emulsion breakers to enhance separation. This is the most critical condition to overcome due to upstream with increasing water content, emulsified, as the stream suffers agitation during the long runs and intricate paths.

You can see API 421, there you will find a procedure to design conventional oil separators. Also, you can use Corrugated plate Separators, are smaller and more efficients than conventional ones.