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Hydrocarbon Dew Point

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#1 CheAmine


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Posted 02 August 2016 - 10:58 PM



Recently we have observed pitting and erosion marks on the turbo-expander blades in one of our NGL recovery units and for that the turbo-expander manufacturer has claimed the possibility of presence of hydrocarbon liquids entering the turbo-expander. A sample at the inlet of the turbo-expander has been collected, analyzed and simulated using HYSYS to estimate the hydrocarbon dew point.Lab analysis is attached. The stream at the inlet of the turbo-expander is usually operating at a temperature of -54 C and a pressure of 49 barg. The hydrocarbon dew point was found to be -48 C at the same operating pressure. Is there a possibility of hydrocarbon liquids drop out at the stream entering the turbo-expander taking into consideration that the turbo-expander upstream separator is equipped with a demister located at the vapor outlet line. note that the vapor line from the turbo-expander separator to the inlet of the turbo-expander does not seem to slop towards the separator.


I have done the same evaluation based on the heat and material balance composition and conditions and I have found that there the temperature and hydrocarbon dew point are equal !


your views regarding this are appreciated.



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#2 serra


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Posted 03 August 2016 - 01:59 AM

(if that is a problem) to avoid the carry over of liquid droplets a few degree of superheating may be required,

a demister may be a good option due to the combined effect with pressure drop,

you may investigate these point with the manufactorer (supposing the original specifications have been modified...),

a software may be useful to predict possible condensation (given composition and operating conditions which you can measure at points of interest)

but at those conditions std. models (Peng Robinson, Soave etc.)  may report a limited condensation (see attched picture, produced with PRODE Properties, should be similar with ASPEN Hysys)

note that you may define C6+ in different ways with different impact on results...

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#3 breizh


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Posted 03 August 2016 - 02:16 AM



Consider this resource to calculate the dew point .




Hope this helps



#4 frosty


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Posted 31 December 2016 - 03:40 AM

Is it possible to post a photo of the observed erosion?  Thanks

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