Propylene moisture (FCC)
Propylene moisture (FCC)
(OP)
Hello,
Does anybody have a problem with a propylene moiusturize immediately after start of the unit?
I had that problem last few years. I am not sure is there problem with a start up procedure or with something else.
First start up procedure was:
- steaming all GCU
- gasification with fuel gas to depropanizer section and intertization of depropanizer, C3 Drier and Propylene spliter section
We change our start up procedure:
- steaming to C3 Drier section
- intertization of Debutanizer, Depropanizer, C3 Drier and Propylene spliter section ( the first two columns and naphtha splitter were not opened)
- intertization of LPG Merox unit
In both case Propylene moisture is appeared and after a few days it droped belows 10ppm.
What is your oppinion? What can be a problem?
Thanks.
Does anybody have a problem with a propylene moiusturize immediately after start of the unit?
I had that problem last few years. I am not sure is there problem with a start up procedure or with something else.
First start up procedure was:
- steaming all GCU
- gasification with fuel gas to depropanizer section and intertization of depropanizer, C3 Drier and Propylene spliter section
We change our start up procedure:
- steaming to C3 Drier section
- intertization of Debutanizer, Depropanizer, C3 Drier and Propylene spliter section ( the first two columns and naphtha splitter were not opened)
- intertization of LPG Merox unit
In both case Propylene moisture is appeared and after a few days it droped belows 10ppm.
What is your oppinion? What can be a problem?
Thanks.





RE: Propylene moisture (FCC)
You need to use dry medium for prolonged time in order to remove/absorb the residual moisture. Gassing up just takes 30min or so, which is definitely not enough to flush all liquid water from the system and to dry up the piping and equipment.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Propylene moisture (FCC)
RE: Propylene moisture (FCC)
If you can't find suitable dry stream/medium, then a heating source would be required to heat up the (wet) medium and increase affinity for absorption of moisture from piping and equipment. See if you can utilize process heaters for that purpose - just remember to perform a dedicated risk assessment for this activity and address all possible issues. This can sometimes be a very hazardous operation.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Propylene moisture (FCC)
Does anybody have a same problem? Or some other recommendation for start-up procedure?
RE: Propylene moisture (FCC)
Try to obtain more effective control over residual moisture removal activity. Perhaps repeat inertization/purge steps till dew point improves, if there is not enough gas for continuous purge.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Propylene moisture (FCC)
In your plant, think the column overheads water cooled condensors ( deC3, deC4 etc) should also be completely drained out and dried also to prevent water ingress into the process side through small leaks in the tube to tubesheet roller expanded joints. There may be other sources of water ingress also.