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I have noticed during simulations of CDU ovhd stream that the dew point temperature increases with the increase of neutralizer dose. Also, I noticed that the pH of the aqueous phase remains low for certain temperature range below mentioned dew point temperature. As I have learned, this point is called ionic dew point and is characterized by lower content of water (therefore high H+ concentration). Does anybody have more experience with this phenomenon? Could it be the reason for severe corrosion in ovhd stream?
 
Answers
01/06/2016 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It is unclear whether your data is from your simulations or from the plant operating data. If the plant is in fact experiencing “severe corrosion,” a change in the treatment design or procedure is needed. If your data is based on software simulations, please note that calculating the water dewpoint of atmospheric overhead has always been inaccurate and should not be used for decision making, in my experience.
31/05/2016 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
It is most definitely a common cause of corrosion in systems that lack a water wash to force the water dew point. Proper neutralizer selection, control of overhead operating conditions, and control of chlorides through good desalting operation and appropriate caustic usage are critical factors in controlling this type of corrosion.