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Separator inlet device

Separator inlet device

(OP)
Hi,
1-It's complicated for me that how to choose inlet device ( no inlet device, half-open pipe, proprietary, cyclone and etc)? Based on what parameters? I know there is standards for that which if you choose half open pipe pv^2< 4200 and etc. But, these standards is used to find min nozzle diameter after deciding inlet device type right? Also, what does proprietary device mean ( special manufactured device or schoepentoeter) ? Some of references say that it's based on g/l ratio. Is that true?
2-If these standards ( pv^2<4200) is used for determining the type of inlet device, then how to calculate velocity without knowing ID of nozzle?
I have excel sheet. Which firstly calculates ID using pv^2 standard then calculates v using this ID then again calculates pv^2 for that velocity. But there is no information why it chose the proprietary inlet device

RE: Separator inlet device

That's why process engineers were invented.

In general your start point is the diameter of your incoming pipe.

You also need to find out what sort of liquid flow you're expecting ( mist, annular, slugging, laminar etc) Only then can you figure out what inlet system is best.

In general the slower the fluid comes in the better for separation purposes.

You have from memory a low liquid gas stream so probably mist or annualar flow. Just expand the nozzle internally in the vessel and point it down.

The inlet is a less trouble than the de-mister pads or devices on the outlet.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Separator inlet device

(OP)
Thanks for information
I - scenario -lets say there are gas and oil streams, which there is no water content in mixture. In that case i think no need to use inlet device, beside using demister pad is necessary which the gas outlet is connected to compressor. And also g/l ratio is high
II- scenario- again there are oil and gas streams, which at this time the mixture contains water. In that case, i think using inlet device and also demister pad in necessary for high efficiency and again gas outlet is connected to compressor.
III-scenario- there are oil and gas stream but this time g/l ratio is low. and there is no water content. Using just inlet device would be enough i think.
What do you think about these scenarios?

RE: Separator inlet device

The aim of a separator is to separate liquids from gases.

Anything you can do to stop mixing of these on entry to a vessel or creating such velocity that it disturbs the liquid level in the vessel is a good thing.

what type of inlet system is best for each of your systems? I don't know, but you need to look at velocity and then take advice from vendors or process engineers. You're getting into fine detail here which needs a very good understanding of your precise inlet parameters and what is best for that particular scenario and that needs knowledge and experience.

Time to start talking to an experienced process engineer or separator vendor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Separator inlet device

(OP)
I'm trying to find their free time. I'm going to crazy to think about that issue. Thanks again for help

RE: Separator inlet device

A large number of inlet devices fall into one of two categories:
  1. Devices that only work in a very narrow range of Reynolds Numbers or Weber Numbers (for rotational flow)
  2. Devices that don't work anywhere
The rest fall into the third category which is "devices that work well for a very narrow function over a wide range of conditions". An inlet coelessor might fit into this last category, but all it does is make droplets bigger, if your flow already has a droplet size that the separator was designed for then a coelessor will not improve performance at all.

To decide what you need, you have to start with what you have (i.e, information about your inlet stream). Does the flow stream tend to be foamy? A foam breaker in front of your vessel might be a good idea. Do the droplets tend to be very small (aerosol or smaller)? A coelessor might be useful. Heavy with solids? An inlet filter could help. None of these? Size your inlet nozzle as I describe in my book (which discusses the pv2 criteria and where it comes from) and get on with your life.

In my experience, inlet dams and swirlly bits before the primary separator are a significant waste of money in almost any actual flow stream (they fit into category 1 at best, usually category 2)

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Separator inlet device

Tha schoepentoeter looks good and has a great name. .... Probably cat 1.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Separator inlet device

Certainly category 1. When I see phrases like "removes kinetic energy from the flow stream", I wonder about where it sends it since energy can neither be created nor destroyed, only changed in form. I just read a half dozen articles about the device, and the only "proof" offered that it does anything at all is CFD model output. A computer model can never "prove" anything (since a half competent modeler can adjust the assumptions to get any result they desire). When marketing relies on CFD (which one modeler of my acquaintance says stands for "Colorful Fluid Dynamics" since everyone is impressed by the colorful model-output), you can be confident that they have nothing else.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Separator inlet device

If you are following the Shell design routine, the basis for the selection of the inlet device would depend on what type of gas exit demister device is selected. There is a upper limit on the permissible liquid entrainment ratio in the vapor stream at the upstream face of the demister device. Select the inlet device to meet this limit. Obviously, for low values of L/G ratio in the feed stream to the sep, a half open pipe may be adequate for any type of gas exit demister, while more elaborate feed devices will be necessary for higher L/G ratio in the sep feedstream. This is what I recall from memory on Shell design procedure.

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