KNOCK OUT VESSEL

[Fizza]

Dear All,

I have following questions about the knock out vessel, the fluid is natural gas, the vessel is vertical

1- What is the acceptable range of the vapor velocity exiting the vessel?
2- What is the acceptable range of the liquid velocity exiting the vessel?
3- Why LCV is used at the outlet line of the liquid exiting the vessel?
4- How the different levels are set i-e LLL, HLL, HHLL, HHLA etc? is there any good engineering practice about this or any thumb rules?
5- Is it required to use mist eliminator made of UNS 08825 for natural gas? I have seen only SS304 eliminators.
6- Please share some renowned vendors for these mist eliminators.
7- What odering information is required for the vendors of mist eliminators?

[dexter]

When ever we talk about limit of velocities of any fluid, we always refer to allowable 'rho*v2' limit. Here rho is the density of fluid at flowing conditions and v is velocities. In a general practice following rhoV2 limits are acceptable, (keep that in mind that these are best practices ONLY).
for Inlet velocity limit; rhoV2 = 1400
for Vapor velocity limit; rhoV2 = 5000

rho will be in Kg/m3
V will be in m/sec

[irish]

5- For sour gas applications, yes.
6- Will have to see
7- Other than the normal ones, dimensional outline drawing, material requirements

[tosif]

Here is the responce to my best knowledge;

dexter has already answered the first two queries, adding one more thing about the inlet Rho.V2 limit depends upon if any inlet device present or not.
3- LCV is used to control the liquid level close to NLL.(Why? please refer to following point)
4- Please refer to http://forums.thepetrostreet.com/viewto ... ?f=10&t=40
5- Materiel of mist eliminated must be carefully selected to avoid corrosion due to possible presence of water, SO2 and CO2.
6- One i know is 'amistco'.
7- In addition to mechanical dimensions of vessel and demister, companies also require the process data to validate the load handling and separation efficiency. Process data include flow, temperature, pressure, density and viscosity of both gas and liquid.

My friend, if you still has any confusion, do let me know.