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We are experiencing seal failures in a heavy naphtha pump (topmost side draw product of the atmospheric crude column) due to blackish muck-like material. the pump suction strainer has been found to be damaged as well. Heavy naphtha draw-off is from the 9th tray from the top. Could it be due to formation of iron sulphides and corrosion of the top tray elements? Anyone else faced similar issues?
 
Answers
04/06/2020 A: Jake Gotham, InSite Technical Services, jake.gotham@insitetechnical.com
Wet chloride, ammonium chloride or amine hydrochloride corrosion are among the possible problems in this system. I’d suggest checking the overhead temperature versus dew point, and also trying to get a sample of reflux return to look for entrained water. Trending the chloride and iron content of the overhead water would be useful, as would data for the iron content of the heavy naphtha draw.

Get in touch if you’d like some help troubleshooting this problem.
28/05/2020 A: Rajkumar Chate, Sulzer, rajkumar.chate@sulzer.com
Corrosion is a common problem in the crude column overhead, particularly in the top few trays. Collect a sample at the pump strainer and analyze it. If you found most of the sample contains inorganic matter then most probably the issue is due to corrosion. In the case of higher % of organic material in the sample, there is a higher possibility that the oil is polymerizing in the top section. This has been particularly observed during shale oil processing.
27/05/2020 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
It is likely corrosion deposits mixed with the salts that caused the corrosion. Salts are likely either ammonium chloride or amine hydrochloride salts. The amine source is usually a tramp amine in the desalted crude. MEA, which is a byproduct from a common H2S scavenger, is one of the most common tramp amines these days. Putting some deposit in water and doing ion chromatography on the resulting water solution can help determine what is causing the corrosion.
27/05/2020 A: Nagarathinam S Murthy, Ashphil Consultancy, Chennai, nssvdvr@gmail.com
It appears that salting of NH4Cl and Amine Hydrochlorides are taking place in this section causing corrosion. Typically we drain off stand by pump on Hy naphtha and top pumparound sections while restarting after prolonged idling. Further, check the margin on top tray against salting temp of both NH4Cl and Amines Hydrochloride. Ideally avoid using Neutralizing Amines as we have seen more nuisance than benefits. Even being used for reasons best known, ask chemical solution provider on the salting point of these amine chlorides and the corrosivity data. Additionally use multi amines (2 or more) for neutralizing, if at all needed rather than single amines. Another control will be to avoid cold reflux from CDU OH accumulator vessel into column which can carry in dissolved salts in water... Good luck..