15 replies to this topic

[refundycom@yahoo.com]

Hi all. I have some enquiry here regarding the sizing of the feed nozzles of the gas-liquid separator.

I have referred to Design Engineering Practise of one of the operator company and I found the equation is:-

− If a half-open pipe is used as inlet device:
ρv2 ≤ 2100 (pa)

The question is what happen if the momentum of the feed is exceed the limit (>2100)...Can you brief me what are the inlet momentum criteria for this matter...thanx

[JoeWong]

Gas-liquid mixture enter into separator via an inlet device (or no device at all). When the mixture entering a separator, if the mixture is

• not well distributed
• not impinged at right angle
• not directed to right path

this will results

• destroy of bulk liquid into droplet form
• large droplet break-out into small droplet
• separated liquid re-entrain into gas

As a result, severe poor gas separation and severe liquid entrainment.

A step further in gas liquid separation is the droplet stability and it is subjected to activities such as breakage, coalescene, deposition and entrainment. All this are linked to the interface between gas and liquid. A few parameters affecting the performance of this interface. There are (as minimum) :

(i) fluid density
(ii) fluid velocity
(iii) characteristic length of the droplet / "defined" surface
(iv) surface tension

Comparatively the first two parameters are dominating the performance in engineering and it is the momentum (ρv2).

If momentum (ρv2) is exceeded, it will affect the gas-liquid separation efficiency.

[fallah]

Joe Wong presented a complete explanation.

Just my general comment:

The momentum value consideration applies where the flow may impact on the equipment (or its components) and also its predefined operation. This parameter determines whether the distributor, impingement plate, wear plate,..... in the front of the inlet nozzle of a separator - are needed or not.

[refundycom@yahoo.com]

Thanks for your explanation. But I still not understand the way they get the value (max momentum) such as for half open pipe pv2>2100. How they manage to get 2100...what's the parameters are they referring to...appreciate your explanation in this matter. TQ

[refundycom@yahoo.com]

Joe Wong,

May I know where did you refer to regarding the pv2 because i need to put it in my report as reference. Thank you pal.

Best regards,

Ridhuan

[Qalander (Chem)]

Ridhuan:

If I am not mistaken, this comes from Rho(density) and v (velocity) of the fluid used to obtain the momentum values in the standard formula.

[JoeWong]

You mentioned
"I have referred to Design Engineering Practise of one of the operator company and I found the equation is:-

− If a half-open pipe is used as inlet device:
ρv2 ≤ 2100 (pa)
"

This is your source (and i knew the source by looking at the figure).

The 2100 Pa in your source is normally based on experiment data and supported by field operating data.

[ankur2061]

Joe,

The standard I prepared for a middle east O&G has a table on momentum values for inlet devices. This table was prepared based on consulting various open source literature and company standards. Below is the table:

Inlet Device Momentum

None ρ_mV²_m,in ≤ 1400 kg/m.s2

Half Open Pipe ρ_mV²_m,in ≤ 2100 kg/m.s2

Schoepentoeter ρ_mV²_m,in ≤ 8000 kg/m.s2

Cyclone (conventional) ρ_mV²_m,in ≤ 10,000 kg/m.s2

Multicyclone ρ_mV²_m,in ≤ 35,000 kg/m.s2

where ρ_m is the mean density of the mixture in inlet pipe, kg/m3 & V_m,in is the velocity of the mixture in the inlet nozzle in m/s.

Hope this information is useful.

Regards,
Ankur.

[sachindhopade]

hope this helps u
http://www.processca...zle_Sizing.aspx

[Afshin445]

Dear Members,
First of all I know this post is old but I have same problem as JoeWong.

I want to use an existing vessel (two phase separator) which is equipped with half open pipe in inlet nozzel for new flowrate condition. When I checked new inlet nozzle momentum is about 32400 Pa which is significantly higher than half open pipe criteria (2100 Pa)
I want to know this nozzle is appropriate for new condition or internal should be chnaged? What happen if we didn't change vessel inlet nozzle internal?
Regards
Afshin

Edited by Afshin, 30 January 2012 - 10:41 PM.

[Afshin445]

Dear Experts,

Any idea?

Regards

[Bharathiraja]

Dear Afshin,

The existing vessel can be re-used after changing the Inlet Nozzle size so that the momentum criteria is satisfied. Looking at your figures, I think your new flowrate is much higher than the earlier one. For this case changing the nozzle size alone is not sufficient. You should also check your separator internals for possible flooding and foaming. I know the standard, which you are referring right now has the equations for flooding and foaming. Alternatively you can use KG Tower program to do your analysis.

[abhi_agrawa]

Afshin,

Inlet nozzle momentum of 32400 Pa is way too high. I would suspect that even the line would not be adequate. I would suggest that the nozzle should be changed. You may like to contact vendors like Sulzer or Koch Glitsch for a special entry device.

abhishek

[Afshin445]

Dear abhi_agrawa/Bharathiraja

Thank you for your responce. But do you think changining of nozzle size is practical? Already, the vessel is installed in the plant.

regards

[Bharathiraja]

Afshin,

Changing the feed nozzle is absolutely possible.

[LITian]

Hello Afshin,

Have you found a way out for reusing the vessel and any solution for the inlet nozzle? I can understand the headache involved in doing a hot work on an installed vessel. If you haven't found a solution yet, there are state-of-the-art inlet devices available which can help you get rid of the hazzles of hot work and eventual re-certification involved and still get you the required size of nozzle to reduce the inlet momentum. If you have a process datasheet that I can look at, please let me know.