3 replies to this topic

Dear everybody,
I need some basic information about demulsifier , how they act and how they are chosen. I would be appreciated anybody who guide me.
actually I work in a gas refinery and our DSO seperator drum has some problem.It should let Air,DSO and NaOH solution make 3 phases but DSO and NaOH does not seperate up to spec,So we are using demulsifier.

sincerely,
Farzaneh

[Zauberberg]

Something general about demulsifier chemistry and emulsion breaking:

http://www.natcogrou...nResolution.pdf
http://www.spe.org/w...-77497-PA-P.pdf
http://www.setlabora...om/demulsif.htm
http://www.chemeng.n...is/ihauflem.pdf
http://www.ifp.fr/IF...pdf?openelement

Is it possible there is something wrong with RSNa oxydation reaction (my guess is that you are talking about spent caustic regeneration)? Check the air rate and catalyst quality (if used). Also, look for particles that may stabilize emulsion. The fact that you do not have clear (DSO/water phase) resolution, might point at some location upstream of phase separator drum, causing incomplete reaction. Did you analize DSO for unoxidized components?

Also, I would suggest you to check level controller operation. Where two liquid phases are involved, standard floating-type level measurement is of very little help.

Zauberberg, Thanks alot for your comment,

First of all, I'm sorry for being late to check my box . then, about our problem ,yes you mentioned correct that it is our spent caustic regeneration unit.we've worked on the air rate and catalyst is O.K also. Actually our problem is in separator drum;because its demister pad had been damaged and we couldn't replace it with the actual type.Also our level controller doesn't work properly.
Our supervisor started injecting demulsifier in this drum.(It is not in licensor operating manual) Now the quality of caustic is O.K and total sulphur is in spec. but we wonder if injecting demulsifier may have side effects or not?

Why did you ask about analysing DSO unoxidized components?

regards,
Farzaneh

[Zauberberg]

Hello Farzaneh,

I was surprised that you have problems with phase separation in caustic regeneration unit - that was the reason I suspected inadequate or incomplete oxydation reaction. The same type of unit exists in our refinery, with no operating problems: it is very simple process.

By measuring unoxidized sulfur components in DSO and regenerated caustic (prior to demulsifier addition), you can determine if your process is running well. If RSNa and Na2S content is within design/acceptable values, then you can focus your troubleshooting efforts on downstream equipment - separation stages of process.
Level control problem is a common issue for two-phase separation (liquid/liquid), causing entrainment of DSO with caustic stream, or reverse.
Concerning the demulsifier side-effects, you must contact your chemicals vendor and search for the answers.

Best regards