Copper Strip corrosion in Propane Product in C3 splitter column bottom

[PetroDDP]

HellO experts !!

Propane is recovered from Unsaturated LPG at Propylene Recovery Unit (PRU) - Propylene tower (C3= splitter) bottom.
We process FCC & Coker Unsat LPG in PRU.

We are facing problem of Copper strip corrosion test failure at Propane eventhough LPG feed to PRU is Okay (Cu corrosion test is as per specification of 1B).

Recently, Propane Product is failed to Cu strip corrosion when Upstream column (DeC2- Deethaniser column) overhead cooling water exchanger was taken in to service after exchanger tube cleaning/repair in-situ.

We have the frequent experience of heavy deposits in the shell side of the Deethaniser overhead exchangers (the analysis of the deposits and deethaniser reciever boot water ionic species analysis is attached).

Is there any possibility of relationship between Cu strip corrosion test failure with the deposits at this exchanger as well as inherent sulfur species coming with LPG feed

Request to throw some lights on Chemistry aspects ?

http://files.engineering.com/getfil...verhead_cooler_Shell_side_depositanalysis.xls

http://files.engineering.com/getfil...a57&file=De-Ethaniser_Boot_water_analysis.xls

Thanks in advance.

 

[SeanB]

A sketch would be helpful to see the process flow. But a first guess would be it sounds like you CW exchanger is leaking water into the process.

 

[PetroDDP]

the unsat LPG is the feed from LPG merox unit. There are 3 columns in this PRU unit.first feed hits in to c3-c4 splitter column,then its overhead goes to deethaniser column and then finally c3 splitter column which splits propylene as overhead and propane as bottom. This problem is pertaining to bottom propane stream.
Cooling water tube side pressure is 4 kg cm2g and shell side is 21 kg cm2g. So, i think it may not be chance.

 

[PetroDDP]

Process Flow diagram of Unsat LPG merox and PRU is attached for your quick reference.

http://files.engineering.com/getfil...2e-0de6fbb1027a&file=PFD_LPG_Merox_&_PRU.pptx

 

[PetroDDP]

Last post attachment was pptx (MS Office 2010) , attaching 2003 version PPT in case if earlier does not open for your convinience.

http://files.engineering.com/getfil...58d-8e5915bb3884&file=PFD_LPG_Merox_&_PRU.ppt

With Warm Regards,

 

[SeanB]

Are you treating your lpg with caustic or amine before feeding it to your gas plant? You may also want to refer to this thread.

http://www.eng-tips.com/viewthread.cfm?qid=264858&page=14

 

[PetroDDP]

We treat with Caustic for RSH and Amine for H2S both.