Calculated demister size to small related to vessel ID? Effective?

[jennymd]

Hi guys,

The design case is based on a gas flowrate that is only 0.2% of the total flow. So, the calculated demister size using GPSA equations is super small (1").
The vessel is designed on the liquid flowrate and residence time (vessel ID 4').

How effective will be to have a mist eliminator of less/equal 4'? Do you recommend this practice?

Should the design just be based on having the pad in a "piece of pipe" in the gas outlet?

The gas outlet flows to a flare.

Thanks a lot for your time and happy holidays.

Jenny

 

[roker]

Hello,

why do you need a demister if the gas flows to the flare, usually the flare system has a KOD to catch liquid.

regards,
roker

 

[gr2vessels]

jenny,
I assume from your post that you have selected a vertical vessel for your separator and for that reason you hit the demister sizing problem. I believe that a horizontal vessel is more suitable for your application, with a small demister (perhaps fitted in a box), at the gas outlet nozzle throat. Obviously, if there are other contaminants likely to clogg the demister, some cleaning/removal arrangement should be included.
Howzat?
cheers,
gr2vessels

 

[djack77494]

Don't forget that one option is to omit a demister altogether. Nothing says that you MUST have a demister; in fact, there are cases where you definitely do not want a demister even if one would result in a smaller vessel.
Doug

 

[jennymd]

Thanks for your answers

I ran a calculation for a horizontal vessel resulting in almost the same size as the vertical result. So, just choosing based on the space in the plot area I went with the vertical drum no demister.