Inlet pipe work of Liquid-Gas Separators

[rhonaba]

Hi Guys,

Can anyone give me some insight or explanation into bubble behaviour on different kinds of pipe geometry (bends) on inlet pipe work into a liquid-gas vertical separators. A brief of my research is as follows:

Gas Void Fraction measured from a gravity Separator with a five 90degree inlet bends pipe layout was very high.

Pipe layout was changed to long radius sweep bends. however, gas void fraction measured was the same. Could there be anything else happening to affect or break gas bubbles?

Thanks.

 

[dcasto]

The 5 90's sounds like an urban myth more than fact or analytical analsys. I could see having large diameter lines with low velocities in order to create slug flow to change the seperation vessels.

 

[katmar]

Changing the pipe size might affect the way bubbles combine or get broken up, but I cannot see it changing the overall void fraction. The void fraction is surely only a function of pressure?

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[rhonaba]

The research is based on investigating the effects of inlet pipe geometries (in terms of bends) on flow conditions into the separator.

On the 5 90deg bends, the flow before the bends was slug. After the bends, the flow became very milky which sort of suggested the bends may be having some effects on the bubble sizes obviously. Hence the research.

The pipe geometry was changed to long-radius bends and the effect was similar.

Obviously, the state of flow into a separator affects its efficiency.

I need some more light of how much influence pipe bends have on 2-phase flow (oil-air). Would there be any other factors that could affect the state of flow?

One other thing I would like anybody to shed light on as well is any relation for estimating the separation time in a vertical separator.

Thanks Guys.

 

[dcasto]

Aw, this is truely two phase, not a gas line with some liquids. The milky color indicates emulsions and foaming in the separator.

Is there water too?

Katmar hits on larger pipe which will allow a laminar flow and lower emulsions. You will still get the mixixg anytime you change directions unless the rate is way down, like .5 ft/sec or something. Typically we use 1 to 4 minutes of surge time. For large amounts of oil and water it may take 30 to 60 minutes to breakout the oil/air/gas.

The GPSA handbook has some good rules of thumb.