Q & A > Question Details
Post Turn Around in Mar-2010, we have been facing issue of C3/C4 splitter re-boiler fouling. This reboiler is at down stream of LPG merox unit. Simultaneously, high delta P has been observed across LPG sand filter. Recently we have opened up the LP sand filter and found some sticky material showing some of fouling material is being slipped through sand filter (partially by passed at times) and accumulating in reboiler. What could be the reasons of fouling in LPG Merox?
Analysis of the sludge collected from the re-boiler was showing mainly HC, 1.5% sodium, ppm levels of silica and iron.
More over lead acetate test was carried out at outlet of sand filter and it was negative showing no sulphur being slipped in treated LPG.
 
Answers
20/07/2012 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
The purpose of sand filter is to trap all the contaminants and leave the Clean LPG to down stream. Normally a water wash vessel will be installed in the upstream of sand filters to wash off all the Caustic traces coming from the Caustic settlers. The partial bypass of sand filters will allow some of the Caustic laden water to rundown along with LPG. Presence of Sodium in the foulants is indicating this. One must keep checking the DP across the sand filters and plan for replacement of sand or water washing of sand when the DP across the sand bed goes high.
07/05/2012 A: Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
The combination of items that you are reporting is certainly strange.
LPG from an FCC unit (as you are likely to have) can be contaminated with higher boiling components after amine treating. This is not something that is in the published literature.
It is somewhat surprising that no sulphur or nitrogen was detected in the deposits.
Are there any other problems with the LPG quality?
Any problems related to alkylation, MTBE, TAME?
Any problems with the amine system like foaming of the regenerator?