Liquid carryover challenges are surprisingly common in refineries, petrochemical plants, gas plants, and similar facilities where a vertical knockout drum or separator with mist elimination equipment installed in it fails to remove free liquid from a process gas stream.
Instead of trying to address or repair symptoms, we look for the root cause which usually involves the mist elimination equipment in the knockout drum. Problems may also include improper elimination device specifications, unacceptable/improper inlet piping (upstream), overloading, uneven velocity profiles, incorrect installations, high liquid viscosity, waxy deposits, liquid slugs, foaming, and several other possibilities.
A similar liquid carryover situation occurred to one of our customers as they experienced shortfall in their dryer bed performance and the subsequent degradation of the dryer beds in their Molecular Sieve Unit. After reviewing the detailed design of upstream equipment, it was concluded that the insufficient performance of the Dryer Inlet Separator was the root cause as the design of the mist elimination equipment had shortfall which may have resulted in liquid carrying over to the Molecular Sieve beds. The challenge for liquid removal was more critical as there was no filter separator downstream of the Inlet Separator. All of the liquid was supposed to be removed through the Inlet Separator only.
The shortfall of the existing design was determined to be:
- Poor removal efficiency of Vane Pack mist eliminators in high pressure services [approx. 80 bar(g)]
- Mal-distribution at the Vane Pack
- Localized velocities exceeding critical velocities
- Probable shattering of liquid droplets caused by upstream perforated plate
AMACS Application Engineering Team proposed a no-weld design solution comprised of an Accuflow™ Inlet Diffuser at inlet to reduce momentum of the incoming stream and establish even flow distribution across the cross-section of the separator, a Mesh Agglomerator for the initial separation step and MAXSWIRL™ Cyclones as the polishing operation step.
The viability of the proposed solution was confirmed by performing a CFD study through a third party to provide unbiased analysis and results.
After the successful installation of AMACS’ proposed design, the Inlet Separator efficiency and overall performance improved substantially resulting in an estimated carryover of ≤ 0.01 USG/MMSCF with an overall efficiency greater than 99.5%.
For more information, please contact AMACS Application Engineering Team at (713) 434-0934 or visit www.amacs.com.