Design Pressure for KO drums in acid gas flare system

[Sawsan311]

Dear all,

for acid gas flare systems, do you agree that considering the non-practicality of installing liquid seal vessels for flashback protection from flare tip and a sealing mechanism, the design pressure of the connected vessels including KO drum shall be 7 barg (or 125 Psig as per API 14 J) to accommodate the potential deflagration if it happens?
Or a lower design pressure can be accepted despite the absence of liquid seal mechanism considering the narrow flammability range of the flared acid gases?

Appreciate your views.

Regards,

 

[georgeverghese]

For new designs, 7barg would be a minimum. For existing acid gas KOD at 350kpag design pressure, would suggest that within 15-30minutes of flare gas purge failure, the CO2 solvent stripping system should be shutdown and the KOD isolated from the flare.
Agreed, a liquid seal will only cause flow instability in acid gas vent flow, particularly at low gas flows.