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Water Dew Point In Cdu Overhead

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Posted 03 January 2022 - 01:36 AM

Dear Sir,


I wanted to know what all factors are responsible for Water Dew Point temp in CDU Overhead circuit. 

This has lot of significance when we talk about overhead system corrosion in CDU.

As per my knowledge, Overhead Vapour Feed Composition , Operating pressure and partial pressure of water vapor are responsible factors for Dew Point Temperature . Out of this, I think , partial pressure of water Vapour can be varied by changing Stripping Strip Flowrate . 

So i wanted to know how to force Water dew point earlier in CDU circuit to minimize the risk of corrosion ??

as we can not vary operating pressure and feed composition also.


How we can change water dew point in overhead CDU  ? 


Also I know this water dew point in CDU overhead is not same as Pure Water Dew Point Temp as heavier hydrocarbons present in mixture will increase water dew point and also higher operating pressure increases water dew point also.


Correct me if my understanding of water dew point is completely wrong here.






#2 SilverShaded


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Posted 03 January 2022 - 11:29 AM

"So i wanted to know how to force Water dew point earlier in CDU circuit to minimize the risk of corrosion ??"

Not sure what you mean by this?  All you can do is try to maintain ovehead temperature well above the water dewpoint.  Heavier naphtha going overhead can help although then your messing about with the refinery economics.


There are various designs which attempt to minimize overhead corrosion, such as double condenser designs and not having tip-top pumparounds, or even having top zero reflux.  Any stream entering the tower at less than the water dewpoint can cause localised corrosion.

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