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Our termosiphon reboilers in SWS unit are corroded after only two years. Column works fine, but the tubes in reboilers are leaking, lids are corroded, full of deposits etc. Pipe from bottom of stripper column to reboiler is plugged, almost 90%. Results are poor quality stripped water (with high H2S and NH3). Tubesheet material is SA 266 Gr.2, tubes SA 179 and shell SA 516 Gr.60.
Shell side (LP steam): 180C deg.
Tube side (stripped water): 130C deg.
What could be the problem?
 
Answers
01/07/2013 A: Satish Angadi, Haldor topsoe, satish.angadi@gmail.com
Higher/better tube metallurgy can be one option but this will not address the cause.
Check what is the concentration of salts in feed to SWS stripper? is it higher?
If salts concentration is normal, is it possible to reduce the steam temperature. I suspect high temperature of steam is causing deposits and hence corrosion.
I would have operated column at lower reboiler return temperatures of 125-126°C , meeting the desired stripping objectives.
29/06/2013 A: Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
There are several possibilities, but a likely one is the composition of the sour water.
What is the pH of the effluent water?
If the pH is low (below 7) it is likely that strong acids are present.
The shell side temperature (180 C) seems high for LP steam.
Thermosiphon reboilers can also create high velocities in the return line and the bottom of the stripper, which takes away the protective FeS film.
More information is required to clarrify the reasons for this corrosion.