4 replies to this topic

[golbarg]

Hello guys,

I was wondering if anyone knows the difference between entraiend caustic and slug caustic. We have a UOP Merox system in place to remove mercaptans and H2S from the unsaturated stream. There is no caustic knockout drum after the marcaptan scrubber and we occasionally see caustic carryover to our Alky plant. Process wise, do you guys know how to avoid these caustic carryovers and how we can tell if we have been experiencing entraiend caustic carryover or slug caustic carryover?

Thanks guys

No, i do not know the difference.
But i will search for answer and when i know it i will post the result.

[iplan]

Hi,

The UOP designed plant I worked had a caustic settler after mercaptan extractor followed by a sand filter to avoid caustic carry over in LPG product. Sometimes, a continuous water wash is also done to eliminate caustic in LPG prior to sand filter.


Thanks
Iplan

[mbeychok]

Golbarg:

A well-designed Merox plant for removing mercaptans from LPG would include a caustic settler, followed by a water wash and then by a salt bed. Look at process flow diagram in this article in the Citizendium online encyclopedia: Merox

If your plant was designed by UOP, then I am very surprised that it has no protection against carry-over or entrainment of caustic. I suspect that perhaps it was not designed by UOP.

[GAURANG PATEL]

Hello guys,

I was wondering if anyone knows the difference between entraiend caustic and slug caustic. We have a UOP Merox system in place to remove mercaptans and H2S from the unsaturated stream. There is no caustic knockout drum after the marcaptan scrubber and we occasionally see caustic carryover to our Alky plant. Process wise, do you guys know how to avoid these caustic carryovers and how we can tell if we have been experiencing entraiend caustic carryover or slug caustic carryover?

Thanks guys

Typical UOP LPG Merox PFD is like:
Caustic extractor - Caustic KOD - Water wash vessel - Sand filter - Salt filter / Pre-coalescer

I am surprised to see that there is no safe guard in your case for entrained caustic removal.

You should consult with UOP itself.