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In a condensate refinery (50 API) where only source of water is the feed (less than 0.2 %) with salt values are less than 2.0 ppm, we have observed huge corrosion in the stripper, atmospheric column and stabilizer overhead line. All the overhead receivers run dry and water quantity is very low. Please note that there is no addition of chemicals like corrosion Inhibitor, neutralizer or ammonia. The top temperature for all the columns (except stabilizer)are in the range of 130-160 deg.C (pressure is 3-6 par). What are the possible reasons and how to prevent the same?
 
Answers
02/10/2015 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
I assume that you also are not desalting the crude. 2ppm of salt is not an unusual number for desalted crude and most refineries with this level of salt would also have a corrosion control program, which you lack. In your case HCl still forms in the furnace, but now with little water or steam in the system, there is not a lot of water to dilute the acids. When the water dewpoint is reached it will be very low pH and lead to aggressive corrosion. If there is some ammonia formation in the furnace too, you could also be getting ammonium chloride salt formation. In your case, a water wash using water recycled from the overhead accumulator boot along with a neutralizing amine and corrosion inhibitor program is probably warranted.
02/10/2015 A: Eugen Goudsmith, Nijhuis Industries, eugen@goudsmith.eu
Could be various reasons. One of them might be the formation of salts which can lead to under deposit corrosion. It is important that you monitor Chlorides and ammonium levels and calculate the salt formation points in the system and where the water dewpoint physically is in the system. There are different ways to deal with this but more info is needed to understand the cause. Suggest you contact a company like Nalco Champion who does these system checks & calculations for you and can advise.