Neutralizing amines are used in PH control in crude distillation over head systems to minimize corrosion. While studying the possibility of using such amines for Vacuum distillation several contradictory points of view appear some approving and some objecting. What do you suggest? We currently use ammonia in our vacuum distillation.
Answers
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07/11/2007
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sam lordo, Becht Engineering, salordo@comcast.net
For many vacuum towers ammonia has been well suited for corrosion control in vacuum towers. However with the processing of poorer quality "opportunity crudes", its suitability as a neutraliser is lacking, not to mention its impact on cut point. As the previous response mentioned, ammonia is not very good if you are beginning to see corrosion in the initial dew point regime, have an increase in strong acids (e.g. hcl), or an increase in weak acids. the only benefit that ammonia has as a neutraliser is that it is easily distributed in the overhead system... this is a key attribute in applying any neutraliser, hence the addition to water is not a good idea as the mass transfer rate of the neutraliser out of a carrier (hydrocarbon or water) is not high enough to be accomplished in the seconds that the droplet is in the overhead line. Organic water based neutralisers have been successfully employed in vacuum overhead system for decades when properly selected and applied.
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05/11/2007
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Hermann Kempen, Kurita Europe GmbH, kempen@kurita.de
At crude distillation overhead systems neutralizing amines are commonly injected together with oil-soluble filming amines to give a good corrosion protection. The neutralizing amines are blends of amines, which give a very good pH profile during the condensation and it is relatively simple to control the pH range. Ammonia is more difficult to adjust correctly between pH 5.5 and 6.5 and being very volatile it will neutralize only at the end of the condensation and not as required during the whole condensation.
At vacuum overhead systems it is also better to inject neutralizer blends together with a water-soluble filming amine as the vacuum overhead system contains mainly sour water
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