Three phase separator sizing

[oyebaba]

thanks to you guys for all your contributions to this forum ,especially for your solutions to my many questions.
l will like you to assist me on how to determine volume flowrate, mixed phase density and volume flow for a three phase separator , especially were slug problem is expected.

 

[gr2vessels]

The principle remains the same;-don't bother trying to rediscover the wheel, leave the three phase separator to the experts, the supplier of the process design and the mechanical design, which is most likely the fabricator and guarantor of the separator vessel, including the demistre of your previous post. You could perhaps investigate what is a shoeppentoeter and check if that's what you need for your slugging process, also you could contact you local Sulzer rep (or similar) for a typical demister datasheet and a typical calculation, so you could learn how to specify a complete separator.
cheers,
gr2vessels

 

[dcasto]

Sizing a separator for for slugs has an infinite set of solutions. The reason is the different ways you will handle the hydrocarbon phase that is released from the slug catcher. The two extremes are: You size the HC liquid system to handle 100% of that phase within 1 minute, and therefore you have very large liquid handling and flash gas system. In this case your slug catcher is very small.

The other end of the spectrum is you only release enough HC liquid so that the flow is almost equal to a steady state rate. In this case the liquid HC and flash gas system is very small and your slug catcher is at the maximum size.

You need to define how you will handle the HC liquid stream and the water phase stream. This will set the residence or build up volume in the slug catcher. You may even size the two extremes and see how the total cost of the system changes. Then plot the cost versus the slug catcher size. Pick an intermeadiate size and design and cost out a total system and plot sive versus cost. You'll see a curve develope. Use that curve to pick the most efficient slug catcher.

What makes it variable too, is if there is already some infastructure for the liquids and flash gas.

 

[MortenA]

cant entirely agree with gr2vesessels

Sometimes a process engineeer in an early phase needs to get a feeling of the size for layout, cost estimation etc. And while vendors are nice people they sometimes simply dont have the time when they cant smell a likely sale (perfectly understandable).

But its not a simple task - The simplest way is to assume the residense time e.g. for oil in water separation and the choose the needed volume. Assume that the vessel is half full and then size for that. GPSA will give you some methode for sizing for gas liquid KO. Shell DEPS contains many usefull info (but if you dont work for shell you will find acess to them limited).

They key issue with 1st stage separators and slugs is that you dont want a slug to trip the HH alarm.

So you need to know you slug size and then check that the inventory of the separator from NL to LHH is more than say a 99% slug (or whatever you feel comftable with).

Now finding slug size: This is to big a subject to be handled here in this forum (and the separator vendor will 100% guranteed be even more in the blind since they (mostly) know things about steel). If you dont know yourself, and dont have inhouse experience then you must find a consultant how knows.

Best regards

Morten