2 replies to this topic

[akshu0023]

Hi,

 

Had a question on design philosophies of separators.

Flare KOD design is to be designed following API 521 whereas separators/scrubbers/knock-out drums following design in API 12J.

My question is if we observe carefully, the only change in the two design philosophies is in the calculation of drag coefficient. For separators design as per 12J, we have 'K' factor which incorporates the drag coefficient (Cd) with standard values based on height and length of the drum given and in case of flare KODs we have the graph of Cd(re)^2 vs Cd to get Cd.

Why do we have this different Cd calculatons? Also, can one design be used to design the other and vice-versa?

Edited by akshu0023, 13 August 2014 - 03:39 AM.

[Bobby Strain]

What you failed to note is that 12J is a design that uses a horizontal mesh demisting pad (vertical gas flow into outlet nozzle). The flare KO drum has none. If you work through the equations, you can find the relationship between K and droplet size. Then you can use a suitable K for KO drum sizing if you wish.

 

Bobby

[Pumumu]

Yes, I agree with Bobby, KO drum doesn't have demisting pad, so you can use K from the correlation with droplet size