CDU overhead :Stability of filming amine at high pH?
What is the pH range at which the film formed by filming amine remains stable? The naturally occurring Fes loses its stability at pH above ~ 7.5. Is there a similar range for stability of film formed by filming amine as well.
Thanks
Answers
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30/03/2020
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Chris Claesen, Ecolab, cclaesen@ecolab.com
Many of the filming chemistries we apply have a broad range of applicability and they can be used to mitigate against low pH conditions seen in crude units as well as the high pH, bisulphide corrosion mechanisms seen on conversion and hydroprocessing units.
When considering how filmers are used on the overhead of a crude distillation unit, one has to consider their role in the overall corrosion control process. The key to controlling overhead corrosion is good desalting, good caustic control practices (if applicable), effective pH control by neutralisation of the low pH sour water and finally, the use of a filming amine corrosion inhibitor.
The filming corrosion inhibitors are surfactants that adsorb readily onto the protective FeS layer present on the equipment surface and on bare metal that is exposed when the FeS layer is disrupted. However if the conditions are such that the FeS layer is unstable, the protection against corrosion by the passive FeS layer is reduced or completely disappears which will lead to higher corrosion rates. In the absence of filmer and under conditions where an FeS layer does not form or is unstable, corrosion rates can exceed 100 or even 1000 mpy. A properly selected filmer can reduce this with 90-99% depending on the specific conditions and dosage. The best situation is where conditions are controlled to assure a stable FeS layer and a suitable filmer is applied to control the remaining corrosion and the corrosion during upset conditions.
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27/03/2020
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A:
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Chris Claesen, Ecolab, cclaesen@ecolab.com
Many of the filming chemistries we apply have a broad range of applicability and they can be used to mitigate against low pH conditions seen in crude units as well as the high pH, bisulphide corrosion mechanisms seen on conversion and hydroprocessing units.
When considering how filmers are used on the overhead of a crude distillation unit, one has to consider their role in the overall corrosion control process. The key to controlling overhead corrosion is good desalting, good caustic control practices (if applicable), effective pH control by neutralisation of the low pH sour water and finally, the use of a filming amine corrosion inhibitor.
The filming corrosion inhibitors are surfactants that adsorb readily onto the protective FeS layer present on the equipment surface and on bare metal that is exposed when the FeS layer is disrupted. However if the conditions are such that the FeS layer is unstable, the protection against corrosion by the passive FeS layer is reduced or completely disappears which will lead to higher corrosion rates. In the absence of filmer and under conditions where an FeS layer does not form or is unstable, corrosion rates can exceed 100 or even 1000 mpy. A properly selected filmer can reduce this with 90-99% depending on the specific conditions and dosage. The best situation is where conditions are controlled to assure a stable FeS layer and a suitable filmer is applied to control the remaining corrosion and the increased corrosion during upset conditions.
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07/03/2020
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Muhammad Faisal, OQ integrated energy company (Oman), engr.faisalfraz@gmail.com
Target pH of CDU-OVHD Drum boot water to be maintained 5.5¬6.5. FES layer will not remove if PH > 6 and for higher range (PH>8).
Also, quality of SW recycling back to finfan also to be checked and maintained. (Cl<30, NH3< 30, Fe<1.0, PH 6¬6.5).
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04/03/2020
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keith bowers, B and B Consulting, kebowers47@gmail.com
You should ask this question of the vendor/maker of the 'filming amine' you are using. If they do not know, why are you a 'test case?'
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