6 replies to this topic

[Rahimd]

Sirs,

 

I have a problem with a wet gas separator. In a dehydration unit, the regeneration gas after the dryers is a wet gas  that contains the adsorbed liquid in a dryers, this wet gas is cooled and then separate the free liquid of the gas in a separator, I have a carryover problems due to the gas oulet line has still remains os free liquid,  I suspect that the demister has a problem for bad design. Could you recommend me how to evaluate this problem? how to confirm that the desmister is not properly designed?

 

Regards,

Rahimd

[Bobby Strain]

You can find what you need at my website. Just GOOGLE my name. If the software there doesn't answer your questions, then visit the links.

 

Bobby

Edited by Bobby Strain, 20 September 2014 - 07:11 PM.

[breizh]

On top of Bobby's suggestion consider reading the documents attached

 

http://www.red-bag.c...sel-sizing.html.

Hope this helps
Breizh

Edited by breizh, 22 September 2014 - 01:09 AM.

[Rahimd]

Hi guys,

I did the rating case, I calculated the critical velocity whitch is an important factor, but the K value for a separator with a mesh pad? how can i find this value? Do i use the K value that shown in the GPSA which is 0.1

 

kind regards

[Pilesar]

1) The GPSA K Value is a good basis for an evaluation, but I do not find where 0.1 is suggested in GPSA for separators with mesh pad. 

2) I have observed mesh pads in service that were damaged, allowing vapor to bypass the mesh.

3) Vendors of mist elimination equipment can help you rate the expected performance of your separator and suggest improvements.

[Supriyo Mukherjee]

The main deciding factor while designing vapor liquid separator is K value.

 

We have been using the K value as 0.107 as per our standard vendor guideline for sizing the vessel. The Value of K is provided by the Demister supplier/manufacturer.

 

From our own designed vapor liquid separators what we have seen is this value of K used works absolutely fine for the Vessels.

There was no liquid carryover in the vessels.

 

Also the demister pads were in fine condition(seen during maintenance)

 

Find the allowable vapor velocity by using formula k((RHOliq-RHOvap)/RHO vap)^0.5

 

Use K=0.107

 

Use design velocity at around 85% for normal pressures(You may follow this from GPSA handbook).

[xavio]

Rahmid,

 

References on vapor-liquid separator are abundant, please dig a little deeper!

 

Check your vessel/demister ID with the above GPSA formula, if you find it is grossly undersized, then enlarge the vessel/demister.

Alternatively you may select vane type demister which allows higher velocity.

Still another choice, you may modify the inlet device so that momentum is reduced before entering the demister.

 

If you don't find it is undersized, then your demister might be broken, corroded, plugged, or displaced; replace it!

 

Good luck!

 

xavio