Can amines cause crude column overhead corrosion ? Also the organic acids generated during processing of crude oil, can they be trapped by amines? Kindly suggest your views.
Answers
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30/08/2020
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Muhammad Faisal, OQ integrated energy company (Oman), engr.faisalfraz@gmail.com
Yes, amine chloride also causes corrosion in the crude column overhead. The crude pH observed is higher due to amine-based H2S scavengers used in upstream operations for meeting TS/H2S requirements for pumping. Amine-based neutralizers at excessive dosage create amine chloride corrosion, especially in the second elbow of the vapour line (or bends).
Crude pH can be lowered by use of an organic acid to destabilize emulsion formation inside the desalter, but excess dosage of organic acid tends to ends up in the crude column overhead with pH fluctuations that can cause corrosion. A balanced dosage must be used.
Presence of amine in crude can be checked by changes in the pH of stripped water (feed to desalter) vs brine pH (leaving desalter). Or check the pH during water draining from the crude tank (highly risky).
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17/08/2020
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sam lordo, Becht Engineering, salordo@comcast.net
I would say that amines are minimally corrosive, but the salts (halide and organic acid) have the higher probability of creating corrosion
Can organic acids be trapped by amines? Yes they can, simple acid-base reaction.. but it also depends on concentration and strength of the amine and acid present.. stronger acids or bases will react with the strongest acids or bases .. however, concentration can influence what reacts with what, in what order .. high concentration of a weak base will react with an acid before a low concentration of a high strength base (kinetics)
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17/08/2020
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Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita-water.com
Berthold Otzisk, Kurita Europe, berthold.otzisk@kurita-water.com
Traditional neutralising amines (mainly alkanolamines) are used as corrosion inhibitors, shifting the initial low pH to a higher level. The recommended pH is in the 5.5 to 6.5 range. Neutralising amines bound the acidic species such as HCl, H2S or organic acids from cracking reactions by forming the corresponding neutralising amine salt. A drawback of such amines is the fact that the formed salts are corrosive with a tendency to precipitate if not enough wash water is used in the CDU overhead system.
It is possible that smaller portions of the amine salts are routed back to the column with the reflux. If not lifted up again with the steam or condensed water, this might cause salt precipitation in the column after some time. There are some known cases where neutralising amines in the wash water are used as desalter wash water, where some amines and their salts again enter the column and foul the top section of the column. Kurita´s ACF Technology can be used for online cleaning to remove neutralising amine and/or ammonium salts. ACF products contain a very strong organic base and dissolve and replace the weaker precipitated neutralising amine salts by forming liquid ACF salts. ACF salts have a very low corrosion potential, unlike corrosive neutralizing amine salts.
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